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  1. 15 4月, 2015 14 次提交
  3. 07 4月, 2015 1 次提交
    • A
      fix mremap() vs. ioctx_kill() race · b2edffdd
      由 Al Viro 提交于 
      teach ->mremap() method to return an error and have it fail for
aio mappings in process of being killed

Note that in case of ->mremap() failure we need to undo move_page_tables()
we'd already done; we could call ->mremap() first, but then the failure of
move_page_tables() would require undoing whatever _successful_ ->mremap()
has done, which would be a lot more headache in general.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      b2edffdd
  5. 26 3月, 2015 9 次提交
    • M
      mm: numa: mark huge PTEs young when clearing NUMA hinting faults · b7b04004
      由 Mel Gorman 提交于 
      Base PTEs are marked young when the NUMA hinting information is cleared
but the same does not happen for huge pages which this patch addresses.

Note that migrated pages are not marked young as the base page migration
code does not assume that migrated pages have been referenced.  This
could be addressed but beyond the scope of this series which is aimed at
Dave Chinners shrink workload that is unlikely to be affected by this
issue.
Signed-off-by: NMel Gorman <mgorman@suse.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b7b04004
    • M
      mm: numa: slow PTE scan rate if migration failures occur · 074c2381
      由 Mel Gorman 提交于 
      Dave Chinner reported the following on https://lkml.org/lkml/2015/3/1/226

  Across the board the 4.0-rc1 numbers are much slower, and the degradation
  is far worse when using the large memory footprint configs. Perf points
  straight at the cause - this is from 4.0-rc1 on the "-o bhash=101073" config:

   -   56.07%    56.07%  [kernel]            [k] default_send_IPI_mask_sequence_phys
      - default_send_IPI_mask_sequence_phys
         - 99.99% physflat_send_IPI_mask
            - 99.37% native_send_call_func_ipi
                 smp_call_function_many
               - native_flush_tlb_others
                  - 99.85% flush_tlb_page
                       ptep_clear_flush
                       try_to_unmap_one
                       rmap_walk
                       try_to_unmap
                       migrate_pages
                       migrate_misplaced_page
                     - handle_mm_fault
                        - 99.73% __do_page_fault
                             trace_do_page_fault
                             do_async_page_fault
                           + async_page_fault
              0.63% native_send_call_func_single_ipi
                 generic_exec_single
                 smp_call_function_single

This is showing excessive migration activity even though excessive
migrations are meant to get throttled.  Normally, the scan rate is tuned
on a per-task basis depending on the locality of faults.  However, if
migrations fail for any reason then the PTE scanner may scan faster if
the faults continue to be remote.  This means there is higher system CPU
overhead and fault trapping at exactly the time we know that migrations
cannot happen.  This patch tracks when migration failures occur and
slows the PTE scanner.
Signed-off-by: NMel Gorman <mgorman@suse.de>
Reported-by: NDave Chinner <david@fromorbit.com>
Tested-by: NDave Chinner <david@fromorbit.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      074c2381
    • M
      mm: numa: preserve PTE write permissions across a NUMA hinting fault · b191f9b1
      由 Mel Gorman 提交于 
      Protecting a PTE to trap a NUMA hinting fault clears the writable bit
and further faults are needed after trapping a NUMA hinting fault to set
the writable bit again.  This patch preserves the writable bit when
trapping NUMA hinting faults.  The impact is obvious from the number of
minor faults trapped during the basis balancing benchmark and the system
CPU usage;

  autonumabench
                                             4.0.0-rc4             4.0.0-rc4
                                              baseline              preserve
  Time System-NUMA01                  107.13 (  0.00%)      103.13 (  3.73%)
  Time System-NUMA01_THEADLOCAL       131.87 (  0.00%)       83.30 ( 36.83%)
  Time System-NUMA02                    8.95 (  0.00%)       10.72 (-19.78%)
  Time System-NUMA02_SMT                4.57 (  0.00%)        3.99 ( 12.69%)
  Time Elapsed-NUMA01                 515.78 (  0.00%)      517.26 ( -0.29%)
  Time Elapsed-NUMA01_THEADLOCAL      384.10 (  0.00%)      384.31 ( -0.05%)
  Time Elapsed-NUMA02                  48.86 (  0.00%)       48.78 (  0.16%)
  Time Elapsed-NUMA02_SMT              47.98 (  0.00%)       48.12 ( -0.29%)

               4.0.0-rc4   4.0.0-rc4
                baseline    preserve
  User          44383.95    43971.89
  System          252.61      201.24
  Elapsed         998.68     1000.94

  Minor Faults   2597249     1981230
  Major Faults       365         364

There is a similar drop in system CPU usage using Dave Chinner's xfsrepair
workload

                                      4.0.0-rc4             4.0.0-rc4
                                       baseline              preserve
  Amean    real-xfsrepair      454.14 (  0.00%)      442.36 (  2.60%)
  Amean    syst-xfsrepair      277.20 (  0.00%)      204.68 ( 26.16%)

The patch looks hacky but the alternatives looked worse.  The tidest was
to rewalk the page tables after a hinting fault but it was more complex
than this approach and the performance was worse.  It's not generally
safe to just mark the page writable during the fault if it's a write
fault as it may have been read-only for COW so that approach was
discarded.
Signed-off-by: NMel Gorman <mgorman@suse.de>
Reported-by: NDave Chinner <david@fromorbit.com>
Tested-by: NDave Chinner <david@fromorbit.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b191f9b1
    • M
      mm: numa: group related processes based on VMA flags instead of page table flags · bea66fbd
      由 Mel Gorman 提交于 
      These are three follow-on patches based on the xfsrepair workload Dave
Chinner reported was problematic in 4.0-rc1 due to changes in page table
management -- https://lkml.org/lkml/2015/3/1/226.

Much of the problem was reduced by commit 53da3bc2 ("mm: fix up numa
read-only thread grouping logic") and commit ba68bc01 ("mm: thp:
Return the correct value for change_huge_pmd").  It was known that the
performance in 3.19 was still better even if is far less safe.  This
series aims to restore the performance without compromising on safety.

For the test of this mail, I'm comparing 3.19 against 4.0-rc4 and the
three patches applied on top

  autonumabench
                                                3.19.0             4.0.0-rc4             4.0.0-rc4             4.0.0-rc4             4.0.0-rc4
                                               vanilla               vanilla          vmwrite-v5r8         preserve-v5r8         slowscan-v5r8
  Time System-NUMA01                  124.00 (  0.00%)      161.86 (-30.53%)      107.13 ( 13.60%)      103.13 ( 16.83%)      145.01 (-16.94%)
  Time System-NUMA01_THEADLOCAL       115.54 (  0.00%)      107.64 (  6.84%)      131.87 (-14.13%)       83.30 ( 27.90%)       92.35 ( 20.07%)
  Time System-NUMA02                    9.35 (  0.00%)       10.44 (-11.66%)        8.95 (  4.28%)       10.72 (-14.65%)        8.16 ( 12.73%)
  Time System-NUMA02_SMT                3.87 (  0.00%)        4.63 (-19.64%)        4.57 (-18.09%)        3.99 ( -3.10%)        3.36 ( 13.18%)
  Time Elapsed-NUMA01                 570.06 (  0.00%)      567.82 (  0.39%)      515.78 (  9.52%)      517.26 (  9.26%)      543.80 (  4.61%)
  Time Elapsed-NUMA01_THEADLOCAL      393.69 (  0.00%)      384.83 (  2.25%)      384.10 (  2.44%)      384.31 (  2.38%)      380.73 (  3.29%)
  Time Elapsed-NUMA02                  49.09 (  0.00%)       49.33 ( -0.49%)       48.86 (  0.47%)       48.78 (  0.63%)       50.94 ( -3.77%)
  Time Elapsed-NUMA02_SMT              47.51 (  0.00%)       47.15 (  0.76%)       47.98 ( -0.99%)       48.12 ( -1.28%)       49.56 ( -4.31%)

                3.19.0   4.0.0-rc4   4.0.0-rc4   4.0.0-rc4   4.0.0-rc4
               vanilla     vanillavmwrite-v5r8preserve-v5r8slowscan-v5r8
  User        46334.60    46391.94    44383.95    43971.89    44372.12
  System        252.84      284.66      252.61      201.24      249.00
  Elapsed      1062.14     1050.96      998.68     1000.94     1026.78

Overall the system CPU usage is comparable and the test is naturally a
bit variable.  The slowing of the scanner hurts numa01 but on this
machine it is an adverse workload and patches that dramatically help it
often hurt absolutely everything else.

Due to patch 2, the fault activity is interesting

                                  3.19.0   4.0.0-rc4   4.0.0-rc4   4.0.0-rc4   4.0.0-rc4
                                 vanilla     vanillavmwrite-v5r8preserve-v5r8slowscan-v5r8
  Minor Faults                   2097811     2656646     2597249     1981230     1636841
  Major Faults                       362         450         365         364         365

Note the impact preserving the write bit across protection updates and
fault reduces faults.

  NUMA alloc hit                 1229008     1217015     1191660     1178322     1199681
  NUMA alloc miss                      0           0           0           0           0
  NUMA interleave hit                  0           0           0           0           0
  NUMA alloc local               1228514     1216317     1190871     1177448     1199021
  NUMA base PTE updates        245706197   240041607   238195516   244704842   115012800
  NUMA huge PMD updates           479530      468448      464868      477573      224487
  NUMA page range updates      491225557   479886983   476207932   489222218   229950144
  NUMA hint faults                659753      656503      641678      656926      294842
  NUMA hint local faults          381604      373963      360478      337585      186249
  NUMA hint local percent             57          56          56          51          63
  NUMA pages migrated            5412140     6374899     6266530     5277468     5755096
  AutoNUMA cost                    5121%       5083%       4994%       5097%       2388%

Here the impact of slowing the PTE scanner on migratrion failures is
obvious as "NUMA base PTE updates" and "NUMA huge PMD updates" are
massively reduced even though the headline performance is very similar.

As xfsrepair was the reported workload here is the impact of the series
on it.

  xfsrepair
                                         3.19.0             4.0.0-rc4             4.0.0-rc4             4.0.0-rc4             4.0.0-rc4
                                        vanilla               vanilla          vmwrite-v5r8         preserve-v5r8         slowscan-v5r8
  Min      real-fsmark        1183.29 (  0.00%)     1165.73 (  1.48%)     1152.78 (  2.58%)     1153.64 (  2.51%)     1177.62 (  0.48%)
  Min      syst-fsmark        4107.85 (  0.00%)     4027.75 (  1.95%)     3986.74 (  2.95%)     3979.16 (  3.13%)     4048.76 (  1.44%)
  Min      real-xfsrepair      441.51 (  0.00%)      463.96 ( -5.08%)      449.50 ( -1.81%)      440.08 (  0.32%)      439.87 (  0.37%)
  Min      syst-xfsrepair      195.76 (  0.00%)      278.47 (-42.25%)      262.34 (-34.01%)      203.70 ( -4.06%)      143.64 ( 26.62%)
  Amean    real-fsmark        1188.30 (  0.00%)     1177.34 (  0.92%)     1157.97 (  2.55%)     1158.21 (  2.53%)     1182.22 (  0.51%)
  Amean    syst-fsmark        4111.37 (  0.00%)     4055.70 (  1.35%)     3987.19 (  3.02%)     3998.72 (  2.74%)     4061.69 (  1.21%)
  Amean    real-xfsrepair      450.88 (  0.00%)      468.32 ( -3.87%)      454.14 ( -0.72%)      442.36 (  1.89%)      440.59 (  2.28%)
  Amean    syst-xfsrepair      199.66 (  0.00%)      290.60 (-45.55%)      277.20 (-38.84%)      204.68 ( -2.51%)      150.55 ( 24.60%)
  Stddev   real-fsmark           4.12 (  0.00%)       10.82 (-162.29%)       4.14 ( -0.28%)        5.98 (-45.05%)        4.60 (-11.53%)
  Stddev   syst-fsmark           2.63 (  0.00%)       20.32 (-671.82%)       0.37 ( 85.89%)       16.47 (-525.59%)      15.05 (-471.79%)
  Stddev   real-xfsrepair        6.87 (  0.00%)        4.55 ( 33.75%)        3.46 ( 49.58%)        1.78 ( 74.12%)        0.52 ( 92.50%)
  Stddev   syst-xfsrepair        3.02 (  0.00%)       10.30 (-241.37%)      13.17 (-336.37%)       0.71 ( 76.63%)        5.00 (-65.61%)
  CoeffVar real-fsmark           0.35 (  0.00%)        0.92 (-164.73%)       0.36 ( -2.91%)        0.52 (-48.82%)        0.39 (-12.10%)
  CoeffVar syst-fsmark           0.06 (  0.00%)        0.50 (-682.41%)       0.01 ( 85.45%)        0.41 (-543.22%)       0.37 (-478.78%)
  CoeffVar real-xfsrepair        1.52 (  0.00%)        0.97 ( 36.21%)        0.76 ( 49.94%)        0.40 ( 73.62%)        0.12 ( 92.33%)
  CoeffVar syst-xfsrepair        1.51 (  0.00%)        3.54 (-134.54%)       4.75 (-214.31%)       0.34 ( 77.20%)        3.32 (-119.63%)
  Max      real-fsmark        1193.39 (  0.00%)     1191.77 (  0.14%)     1162.90 (  2.55%)     1166.66 (  2.24%)     1188.50 (  0.41%)
  Max      syst-fsmark        4114.18 (  0.00%)     4075.45 (  0.94%)     3987.65 (  3.08%)     4019.45 (  2.30%)     4082.80 (  0.76%)
  Max      real-xfsrepair      457.80 (  0.00%)      474.60 ( -3.67%)      457.82 ( -0.00%)      444.42 (  2.92%)      441.03 (  3.66%)
  Max      syst-xfsrepair      203.11 (  0.00%)      303.65 (-49.50%)      294.35 (-44.92%)      205.33 ( -1.09%)      155.28 ( 23.55%)

The really relevant lines as syst-xfsrepair which is the system CPU
usage when running xfsrepair.  Note that on my machine the overhead was
45% higher on 4.0-rc4 which may be part of what Dave is seeing.  Once we
preserve the write bit across faults, it's only 2.51% higher on average.
With the full series applied, system CPU usage is 24.6% lower on
average.

Again, the impact of preserving the write bit on minor faults is obvious
and the impact of slowing scanning after migration failures is obvious
on the PTE updates.  Note also that the number of pages migrated is much
reduced even though the headline performance is comparable.

                                  3.19.0   4.0.0-rc4   4.0.0-rc4   4.0.0-rc4   4.0.0-rc4
                                 vanilla     vanillavmwrite-v5r8preserve-v5r8slowscan-v5r8
  Minor Faults                 153466827   254507978   249163829   153501373   105737890
  Major Faults                       610         702         690         649         724
  NUMA base PTE updates        217735049   210756527   217729596   216937111   144344993
  NUMA huge PMD updates           129294       85044      106921      127246       79887
  NUMA pages migrated           21938995    29705270    28594162    22687324    16258075

                        3.19.0   4.0.0-rc4   4.0.0-rc4   4.0.0-rc4   4.0.0-rc4
                       vanilla     vanillavmwrite-v5r8preserve-v5r8slowscan-v5r8
  Mean sdb-avgqusz       13.47        2.54        2.55        2.47        2.49
  Mean sdb-avgrqsz      202.32      140.22      139.50      139.02      138.12
  Mean sdb-await         25.92        5.09        5.33        5.02        5.22
  Mean sdb-r_await        4.71        0.19        0.83        0.51        0.11
  Mean sdb-w_await      104.13        5.21        5.38        5.05        5.32
  Mean sdb-svctm          0.59        0.13        0.14        0.13        0.14
  Mean sdb-rrqm           0.16        0.00        0.00        0.00        0.00
  Mean sdb-wrqm           3.59     1799.43     1826.84     1812.21     1785.67
  Max  sdb-avgqusz      111.06       12.13       14.05       11.66       15.60
  Max  sdb-avgrqsz      255.60      190.34      190.01      187.33      191.78
  Max  sdb-await        168.24       39.28       49.22       44.64       65.62
  Max  sdb-r_await      660.00       52.00      280.00       76.00       12.00
  Max  sdb-w_await     7804.00       39.28       49.22       44.64       65.62
  Max  sdb-svctm          4.00        2.82        2.86        1.98        2.84
  Max  sdb-rrqm           8.30        0.00        0.00        0.00        0.00
  Max  sdb-wrqm          34.20     5372.80     5278.60     5386.60     5546.15

FWIW, I also checked SPECjbb in different configurations but it's
similar observations -- minor faults lower, PTE update activity lower
and performance is roughly comparable against 3.19.

This patch (of 3):

Threads that share writable data within pages are grouped together as
related tasks.  This decision is based on whether the PTE is marked
dirty which is subject to timing races between the PTE scanner update
and when the application writes the page.  If the page is file-backed,
then background flushes and sync also affect placement.  This is
unpredictable behaviour which is impossible to reason about so this
patch makes grouping decisions based on the VMA flags.
Signed-off-by: NMel Gorman <mgorman@suse.de>
Reported-by: NDave Chinner <david@fromorbit.com>
Tested-by: NDave Chinner <david@fromorbit.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      bea66fbd
    • L
      mm/page_alloc.c: call kernel_map_pages in unset_migrateype_isolate · cfa86943
      由 Laura Abbott 提交于 
      Commit 3c605096 ("mm/page_alloc: restrict max order of merging on
isolated pageblock") changed the logic of unset_migratetype_isolate to
check the buddy allocator and explicitly call __free_pages to merge.

The page that is being freed in this path never had prep_new_page called
so set_page_refcounted is called explicitly but there is no call to
kernel_map_pages.  With the default kernel_map_pages this is mostly
harmless but if kernel_map_pages does any manipulation of the page
tables (unmapping or setting pages to read only) this may trigger a
fault:

    alloc_contig_range test_pages_isolated(ceb00, ced00) failed
    Unable to handle kernel paging request at virtual address ffffffc0cec00000
    pgd = ffffffc045fc4000
    [ffffffc0cec00000] *pgd=0000000000000000
    Internal error: Oops: 9600004f [#1] PREEMPT SMP
    Modules linked in: exfatfs
    CPU: 1 PID: 23237 Comm: TimedEventQueue Not tainted 3.10.49-gc72ad36-dirty #1
    task: ffffffc03de52100 ti: ffffffc015388000 task.ti: ffffffc015388000
    PC is at memset+0xc8/0x1c0
    LR is at kernel_map_pages+0x1ec/0x244

Fix this by calling kernel_map_pages to ensure the page is set in the
page table properly

Fixes: 3c605096 ("mm/page_alloc: restrict max order of merging on isolated pageblock")
Signed-off-by: NLaura Abbott <lauraa@codeaurora.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: NRik van Riel <riel@redhat.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Gioh Kim <gioh.kim@lge.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      cfa86943
    • M
      mm/slub: fix lockups on PREEMPT && !SMP kernels · 859b7a0e
      由 Mark Rutland 提交于 
      Commit 9aabf810 ("mm/slub: optimize alloc/free fastpath by removing
preemption on/off") introduced an occasional hang for kernels built with
CONFIG_PREEMPT && !CONFIG_SMP.

The problem is the following loop the patch introduced to
slab_alloc_node and slab_free:

    do {
        tid = this_cpu_read(s->cpu_slab->tid);
        c = raw_cpu_ptr(s->cpu_slab);
    } while (IS_ENABLED(CONFIG_PREEMPT) && unlikely(tid != c->tid));

GCC 4.9 has been observed to hoist the load of c and c->tid above the
loop for !SMP kernels (as in this case raw_cpu_ptr(x) is compile-time
constant and does not force a reload).  On arm64 the generated assembly
looks like:

         ldr     x4, [x0,#8]
  loop:
         ldr     x1, [x0,#8]
         cmp     x1, x4
         b.ne    loop

If the thread is preempted between the load of c->tid (into x1) and tid
(into x4), and an allocation or free occurs in another thread (bumping
the cpu_slab's tid), the thread will be stuck in the loop until
s->cpu_slab->tid wraps, which may be forever in the absence of
allocations/frees on the same CPU.

This patch changes the loop condition to access c->tid with READ_ONCE.
This ensures that the value is reloaded even when the compiler would
otherwise assume it could cache the value, and also ensures that the
load will not be torn.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: NChristoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Steve Capper <steve.capper@linaro.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      859b7a0e
    • G
      mm/memory hotplug: postpone the reset of obsolete pgdat · b0dc3a34
      由 Gu Zheng 提交于 
      Qiu Xishi reported the following BUG when testing hot-add/hot-remove node under
stress condition:

  BUG: unable to handle kernel paging request at 0000000000025f60
  IP: next_online_pgdat+0x1/0x50
  PGD 0
  Oops: 0000 [#1] SMP
  ACPI: Device does not support D3cold
  Modules linked in: fuse nls_iso8859_1 nls_cp437 vfat fat loop dm_mod coretemp mperf crc32c_intel ghash_clmulni_intel aesni_intel ablk_helper cryptd lrw gf128mul glue_helper aes_x86_64 pcspkr microcode igb dca i2c_algo_bit ipv6 megaraid_sas iTCO_wdt i2c_i801 i2c_core iTCO_vendor_support tg3 sg hwmon ptp lpc_ich pps_core mfd_core acpi_pad rtc_cmos button ext3 jbd mbcache sd_mod crc_t10dif scsi_dh_alua scsi_dh_rdac scsi_dh_hp_sw scsi_dh_emc scsi_dh ahci libahci libata scsi_mod [last unloaded: rasf]
  CPU: 23 PID: 238 Comm: kworker/23:1 Tainted: G           O 3.10.15-5885-euler0302 #1
  Hardware name: HUAWEI TECHNOLOGIES CO.,LTD. Huawei N1/Huawei N1, BIOS V100R001 03/02/2015
  Workqueue: events vmstat_update
  task: ffffa800d32c0000 ti: ffffa800d32ae000 task.ti: ffffa800d32ae000
  RIP: 0010: next_online_pgdat+0x1/0x50
  RSP: 0018:ffffa800d32afce8  EFLAGS: 00010286
  RAX: 0000000000001440 RBX: ffffffff81da53b8 RCX: 0000000000000082
  RDX: 0000000000000000 RSI: 0000000000000082 RDI: 0000000000000000
  RBP: ffffa800d32afd28 R08: ffffffff81c93bfc R09: ffffffff81cbdc96
  R10: 00000000000040ec R11: 00000000000000a0 R12: ffffa800fffb3440
  R13: ffffa800d32afd38 R14: 0000000000000017 R15: ffffa800e6616800
  FS:  0000000000000000(0000) GS:ffffa800e6600000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000025f60 CR3: 0000000001a0b000 CR4: 00000000001407e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
    refresh_cpu_vm_stats+0xd0/0x140
    vmstat_update+0x11/0x50
    process_one_work+0x194/0x3d0
    worker_thread+0x12b/0x410
    kthread+0xc6/0xd0
    ret_from_fork+0x7c/0xb0

The cause is the "memset(pgdat, 0, sizeof(*pgdat))" at the end of
try_offline_node, which will reset all the content of pgdat to 0, as the
pgdat is accessed lock-free, so that the users still using the pgdat
will panic, such as the vmstat_update routine.

process A:				offline node XX:

vmstat_updat()
   refresh_cpu_vm_stats()
     for_each_populated_zone()
       find online node XX
     cond_resched()
					offline cpu and memory, then try_offline_node()
					node_set_offline(nid), and memset(pgdat, 0, sizeof(*pgdat))
       zone = next_zone(zone)
         pg_data_t *pgdat = zone->zone_pgdat;  // here pgdat is NULL now
           next_online_pgdat(pgdat)
             next_online_node(pgdat->node_id);  // NULL pointer access

So the solution here is postponing the reset of obsolete pgdat from
try_offline_node() to hotadd_new_pgdat(), and just resetting
pgdat->nr_zones and pgdat->classzone_idx to be 0 rather than the memset
0 to avoid breaking pointer information in pgdat.
Signed-off-by: NGu Zheng <guz.fnst@cn.fujitsu.com>
Reported-by: NXishi Qiu <qiuxishi@huawei.com>
Suggested-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Xie XiuQi <xiexiuqi@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b0dc3a34
    • N
      mm/pagewalk.c: prevent positive return value of walk_page_test() from being passed to callers · f6837395
      由 Naoya Horiguchi 提交于 
      walk_page_test() is purely pagewalk's internal stuff, and its positive
return values are not intended to be passed to the callers of pagewalk.

However, in the current code if the last vma in the do-while loop in
walk_page_range() happens to return a positive value, it leaks outside
walk_page_range().  So the user visible effect is invalid/unexpected
return value (according to the reporter, mbind() causes it.)

This patch fixes it simply by reinitializing the return value after
checked.

Another exposed interface, walk_page_vma(), already returns 0 for such
cases so no problem.

Fixes: fafaa426 ("pagewalk: improve vma handling")
Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: NKazutomo Yoshii <kazutomo.yoshii@gmail.com>
Reported-by: NKazutomo Yoshii <kazutomo.yoshii@gmail.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      f6837395
    • L
      mm: fix anon_vma->degree underflow in anon_vma endless growing prevention · 3fe89b3e
      由 Leon Yu 提交于 
      I have constantly stumbled upon "kernel BUG at mm/rmap.c:399!" after
upgrading to 3.19 and had no luck with 4.0-rc1 neither.

So, after looking into new logic introduced by commit 7a3ef208 ("mm:
prevent endless growth of anon_vma hierarchy"), I found chances are that
unlink_anon_vmas() is called without incrementing dst->anon_vma->degree
in anon_vma_clone() due to allocation failure.  If dst->anon_vma is not
NULL in error path, its degree will be incorrectly decremented in
unlink_anon_vmas() and eventually underflow when exiting as a result of
another call to unlink_anon_vmas().  That's how "kernel BUG at
mm/rmap.c:399!" is triggered for me.

This patch fixes the underflow by dropping dst->anon_vma when allocation
fails.  It's safe to do so regardless of original value of dst->anon_vma
because dst->anon_vma doesn't have valid meaning if anon_vma_clone()
fails.  Besides, callers don't care dst->anon_vma in such case neither.

Also suggested by Michal Hocko, we can clean up vma_adjust() a bit as
anon_vma_clone() now does the work.

[akpm@linux-foundation.org: tweak comment]
Fixes: 7a3ef208 ("mm: prevent endless growth of anon_vma hierarchy")
Signed-off-by: NLeon Yu <chianglungyu@gmail.com>
Signed-off-by: NKonstantin Khlebnikov <koct9i@gmail.com>
Reviewed-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NRik van Riel <riel@redhat.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3fe89b3e
  7. 25 3月, 2015 1 次提交
  9. 23 3月, 2015 1 次提交
    • T
      writeback: fix possible underflow in write bandwidth calculation · c72efb65
      由 Tejun Heo 提交于 
      From 1ebf33901ecc75d9496862dceb1ef0377980587c Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 23 Mar 2015 00:08:19 -0400

2f800fbd ("writeback: fix dirtied pages accounting on redirty")
introduced account_page_redirty() which reverts stat updates for a
redirtied page, making BDI_DIRTIED no longer monotonically increasing.

bdi_update_write_bandwidth() uses the delta in BDI_DIRTIED as the
basis for bandwidth calculation.  While unlikely, since the above
patch, the newer value may be lower than the recorded past value and
underflow the bandwidth calculation leading to a wild result.

Fix it by subtracing min of the old and new values when calculating
delta.  AFAIK, there hasn't been any report of it happening but the
resulting erratic behavior would be non-critical and temporary, so
it's possible that the issue is happening without being reported.  The
risk of the fix is very low, so tagged for -stable.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Greg Thelen <gthelen@google.com>
Fixes: 2f800fbd ("writeback: fix dirtied pages accounting on redirty")
Cc: stable@vger.kernel.org
Signed-off-by: NJens Axboe <axboe@fb.com>
      c72efb65
  11. 13 3月, 2015 8 次提交
  13. 12 3月, 2015 1 次提交
    • L
      mm: fix up numa read-only thread grouping logic · 53da3bc2
      由 Linus Torvalds 提交于 
      Dave Chinner reported that commit 4d942466 ("mm: convert
p[te|md]_mknonnuma and remaining page table manipulations") slowed down
his xfsrepair test enormously.  In particular, it was using more system
time due to extra TLB flushing.

The ultimate reason turns out to be how the change to use the regular
page table accessor functions broke the NUMA grouping logic.  The old
special mknuma/mknonnuma code accessed the page table present bit and
the magic NUMA bit directly, while the new code just changes the page
protections using PROT_NONE and the regular vma protections.

That sounds equivalent, and from a fault standpoint it really is, but a
subtle side effect is that the *other* protection bits of the page table
entries also change.  And the code to decide how to group the NUMA
entries together used the writable bit to decide whether a particular
page was likely to be shared read-only or not.

And with the change to make the NUMA handling use the regular permission
setting functions, that writable bit was basically always cleared for
private mappings due to COW.  So even if the page actually ends up being
written to in the end, the NUMA balancing would act as if it was always
shared RO.

This code is a heuristic anyway, so the fix - at least for now - is to
instead check whether the page is dirty rather than writable.  The bit
doesn't change with protection changes.

NOTE! This also adds a FIXME comment to revisit this issue,

Not only should we probably re-visit the whole "is this a shared
read-only page" heuristic (we might want to take the vma permissions
into account and base this more on those than the per-page ones, and
also look at whether the particular access that triggers it is a write
or not), but the whole COW issue shows that we should think about the
NUMA fault handling some more.

For example, maybe we should do the early-COW thing that a regular fault
does.  Or maybe we should accept that while using the same bits as
PROTNONE was a good thing (and got rid of the specual NUMA bit), we
might still want to just preseve the other protection bits across NUMA
faulting.

Those are bigger questions, left for later.  This just fixes up the
heuristic so that it at least approximates working again.  More analysis
and work needed.
Reported-by: NDave Chinner <david@fromorbit.com>
Tested-by: NMel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      53da3bc2
  15. 04 3月, 2015 1 次提交
    • T
      writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth() · 7d70e154
      由 Tejun Heo 提交于 
      global_update_bandwidth() uses static variable update_time as the
timestamp for the last update but forgets to initialize it to
INITIALIZE_JIFFIES.

This means that global_dirty_limit will be 5 mins into the future on
32bit and some large amount jiffies into the past on 64bit.  This
isn't critical as the only effect is that global_dirty_limit won't be
updated for the first 5 mins after booting on 32bit machines,
especially given the auxiliary nature of global_dirty_limit's role -
protecting against global dirty threshold's sudden dips; however, it
does lead to unintended suboptimal behavior.  Fix it.

Fixes: c42843f2 ("writeback: introduce smoothed global dirty limit")
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NJan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: stable@vger.kernel.org
Signed-off-by: NJens Axboe <axboe@fb.com>
      7d70e154
  17. 01 3月, 2015 4 次提交
    • J
      mm: page_alloc: revert inadvertent !__GFP_FS retry behavior change · cc873177
      由 Johannes Weiner 提交于 
      Historically, !__GFP_FS allocations were not allowed to invoke the OOM
killer once reclaim had failed, but nevertheless kept looping in the
allocator.

Commit 9879de73 ("mm: page_alloc: embed OOM killing naturally into
allocation slowpath"), which should have been a simple cleanup patch,
accidentally changed the behavior to aborting the allocation at that
point.  This creates problems with filesystem callers (?) that currently
rely on the allocator waiting for other tasks to intervene.

Revert the behavior as it shouldn't have been changed as part of a
cleanup patch.

Fixes: 9879de73 ("mm: page_alloc: embed OOM killing naturally into allocation slowpath")
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Reported-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Dave Chinner <david@fromorbit.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: <stable@vger.kernel.org>	[3.19.x]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      cc873177
    • J
      mm: memcontrol: use "max" instead of "infinity" in control knobs · d2973697
      由 Johannes Weiner 提交于 
      The memcg control knobs indicate the highest possible value using the
symbolic name "infinity", which is long and awkward to type.

Switch to the string "max", which is just as descriptive but shorter and
sweeter.

This changes a user interface, so do it before the release and before
the development flag is dropped from the default hierarchy.
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d2973697
    • M
      memcg: fix low limit calculation · 4e54dede
      由 Michal Hocko 提交于 
      A memcg is considered low limited even when the current usage is equal to
the low limit.  This leads to interesting side effects e.g.
groups/hierarchies with no memory accounted are considered protected and
so the reclaim will emit MEMCG_LOW event when encountering them.

Another and much bigger issue was reported by Joonsoo Kim.  He has hit a
NULL ptr dereference with the legacy cgroup API which even doesn't have
low limit exposed.  The limit is 0 by default but the initial check fails
for memcg with 0 consumption and parent_mem_cgroup() would return NULL if
use_hierarchy is 0 and so page_counter_read would try to dereference NULL.

I suppose that the current implementation is just an overlook because the
documentation in Documentation/cgroups/unified-hierarchy.txt says:

  "The memory.low boundary on the other hand is a top-down allocated
  reserve.  A cgroup enjoys reclaim protection when it and all its
  ancestors are below their low boundaries"

Fix the usage and the low limit comparision in mem_cgroup_low accordingly.

Fixes: 241994ed (mm: memcontrol: default hierarchy interface for memory)
Reported-by: NJoonsoo Kim <js1304@gmail.com>
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      4e54dede
    • J
      mm/nommu: fix memory leak · da616534
      由 Joonsoo Kim 提交于 
      Maxime reported the following memory leak regression due to commit
dbc8358c ("mm/nommu: use alloc_pages_exact() rather than its own
implementation").

On v3.19, I am facing a memory leak.  Each time I run a command one page
is lost.  Here an example with busybox's free command:

  / # free
               total       used       free     shared    buffers     cached
  Mem:          7928       1972       5956          0          0        492
  -/+ buffers/cache:       1480       6448
  / # free
               total       used       free     shared    buffers     cached
  Mem:          7928       1976       5952          0          0        492
  -/+ buffers/cache:       1484       6444
  / # free
               total       used       free     shared    buffers     cached
  Mem:          7928       1980       5948          0          0        492
  -/+ buffers/cache:       1488       6440
  / # free
               total       used       free     shared    buffers     cached
  Mem:          7928       1984       5944          0          0        492
  -/+ buffers/cache:       1492       6436
  / # free
               total       used       free     shared    buffers     cached
  Mem:          7928       1988       5940          0          0        492
  -/+ buffers/cache:       1496       6432

At some point, the system fails to sastisfy 256KB allocations:

  free: page allocation failure: order:6, mode:0xd0
  CPU: 0 PID: 67 Comm: free Not tainted 3.19.0-05389-gacf2cf1-dirty #64
  Hardware name: STM32 (Device Tree Support)
    show_stack+0xb/0xc
    warn_alloc_failed+0x97/0xbc
    __alloc_pages_nodemask+0x295/0x35c
    __get_free_pages+0xb/0x24
    alloc_pages_exact+0x19/0x24
    do_mmap_pgoff+0x423/0x658
    vm_mmap_pgoff+0x3f/0x4e
    load_flat_file+0x20d/0x4f8
    load_flat_binary+0x3f/0x26c
    search_binary_handler+0x51/0xe4
    do_execveat_common+0x271/0x35c
    do_execve+0x19/0x1c
    ret_fast_syscall+0x1/0x4a
  Mem-info:
  Normal per-cpu:
  CPU    0: hi:    0, btch:   1 usd:   0
  active_anon:0 inactive_anon:0 isolated_anon:0
   active_file:0 inactive_file:0 isolated_file:0
   unevictable:123 dirty:0 writeback:0 unstable:0
   free:1515 slab_reclaimable:17 slab_unreclaimable:139
   mapped:0 shmem:0 pagetables:0 bounce:0
   free_cma:0
  Normal free:6060kB min:352kB low:440kB high:528kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:492kB isolated(anon):0ks
  lowmem_reserve[]: 0 0
  Normal: 23*4kB (U) 22*8kB (U) 24*16kB (U) 23*32kB (U) 23*64kB (U) 23*128kB (U) 1*256kB (U) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 6060kB
  123 total pagecache pages
  2048 pages of RAM
  1538 free pages
  66 reserved pages
  109 slab pages
  -46 pages shared
  0 pages swap cached
  nommu: Allocation of length 221184 from process 67 (free) failed
  Normal per-cpu:
  CPU    0: hi:    0, btch:   1 usd:   0
  active_anon:0 inactive_anon:0 isolated_anon:0
   active_file:0 inactive_file:0 isolated_file:0
   unevictable:123 dirty:0 writeback:0 unstable:0
   free:1515 slab_reclaimable:17 slab_unreclaimable:139
   mapped:0 shmem:0 pagetables:0 bounce:0
   free_cma:0
  Normal free:6060kB min:352kB low:440kB high:528kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:492kB isolated(anon):0ks
  lowmem_reserve[]: 0 0
  Normal: 23*4kB (U) 22*8kB (U) 24*16kB (U) 23*32kB (U) 23*64kB (U) 23*128kB (U) 1*256kB (U) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 6060kB
  123 total pagecache pages
  Unable to allocate RAM for process text/data, errno 12 SEGV

This problem happens because we allocate ordered page through
__get_free_pages() in do_mmap_private() in some cases and we try to free
individual pages rather than ordered page in free_page_series().  In
this case, freeing pages whose refcount is not 0 won't be freed to the
page allocator so memory leak happens.

To fix the problem, this patch changes __get_free_pages() to
alloc_pages_exact() since alloc_pages_exact() returns
physically-contiguous pages but each pages are refcounted.

Fixes: dbc8358c ("mm/nommu: use alloc_pages_exact() rather than its own implementation").
Reported-by: NMaxime Coquelin <mcoquelin.stm32@gmail.com>
Tested-by: NMaxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <stable@vger.kernel.org>	[3.19]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      da616534