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  1. 10 5月, 2007 3 次提交
  3. 09 5月, 2007 2 次提交
  5. 08 5月, 2007 14 次提交
  7. 03 5月, 2007 1 次提交
  9. 04 4月, 2007 1 次提交
  11. 02 3月, 2007 1 次提交
  13. 21 2月, 2007 1 次提交
  15. 12 2月, 2007 6 次提交
  17. 06 1月, 2007 1 次提交
  19. 23 12月, 2006 2 次提交
  21. 14 12月, 2006 4 次提交
    • E
      [PATCH] SLAB: use a multiply instead of a divide in obj_to_index() · 6a2d7a95
      由 Eric Dumazet 提交于 
      When some objects are allocated by one CPU but freed by another CPU we can
consume lot of cycles doing divides in obj_to_index().

(Typical load on a dual processor machine where network interrupts are
handled by one particular CPU (allocating skbufs), and the other CPU is
running the application (consuming and freeing skbufs))

Here on one production server (dual-core AMD Opteron 285), I noticed this
divide took 1.20 % of CPU_CLK_UNHALTED events in kernel.  But Opteron are
quite modern cpus and the divide is much more expensive on oldest
architectures :

On a 200 MHz sparcv9 machine, the division takes 64 cycles instead of 1
cycle for a multiply.

Doing some math, we can use a reciprocal multiplication instead of a divide.

If we want to compute V = (A / B)  (A and B being u32 quantities)
we can instead use :

V = ((u64)A * RECIPROCAL(B)) >> 32 ;

where RECIPROCAL(B) is precalculated to ((1LL << 32) + (B - 1)) / B

Note :

I wrote pure C code for clarity. gcc output for i386 is not optimal but
acceptable :

mull   0x14(%ebx)
mov    %edx,%eax // part of the >> 32
xor     %edx,%edx // useless
mov    %eax,(%esp) // could be avoided
mov    %edx,0x4(%esp) // useless
mov    (%esp),%ebx

[akpm@osdl.org: small cleanups]
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      6a2d7a95
    • P
      [PATCH] cpuset: rework cpuset_zone_allowed api · 02a0e53d
      由 Paul Jackson 提交于 
      Elaborate the API for calling cpuset_zone_allowed(), so that users have to
explicitly choose between the two variants:

  cpuset_zone_allowed_hardwall()
  cpuset_zone_allowed_softwall()

Until now, whether or not you got the hardwall flavor depended solely on
whether or not you or'd in the __GFP_HARDWALL gfp flag to the gfp_mask
argument.

If you didn't specify __GFP_HARDWALL, you implicitly got the softwall
version.

Unfortunately, this meant that users would end up with the softwall version
without thinking about it.  Since only the softwall version might sleep,
this led to bugs with possible sleeping in interrupt context on more than
one occassion.

The hardwall version requires that the current tasks mems_allowed allows
the node of the specified zone (or that you're in interrupt or that
__GFP_THISNODE is set or that you're on a one cpuset system.)

The softwall version, depending on the gfp_mask, might allow a node if it
was allowed in the nearest enclusing cpuset marked mem_exclusive (which
requires taking the cpuset lock 'callback_mutex' to evaluate.)

This patch removes the cpuset_zone_allowed() call, and forces the caller to
explicitly choose between the hardwall and the softwall case.

If the caller wants the gfp_mask to determine this choice, they should (1)
be sure they can sleep or that __GFP_HARDWALL is set, and (2) invoke the
cpuset_zone_allowed_softwall() routine.

This adds another 100 or 200 bytes to the kernel text space, due to the few
lines of nearly duplicate code at the top of both cpuset_zone_allowed_*
routines.  It should save a few instructions executed for the calls that
turned into calls of cpuset_zone_allowed_hardwall, thanks to not having to
set (before the call) then check (within the call) the __GFP_HARDWALL flag.

For the most critical call, from get_page_from_freelist(), the same
instructions are executed as before -- the old cpuset_zone_allowed()
routine it used to call is the same code as the
cpuset_zone_allowed_softwall() routine that it calls now.

Not a perfect win, but seems worth it, to reduce this chance of hitting a
sleeping with irq off complaint again.
Signed-off-by: NPaul Jackson <pj@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      02a0e53d
    • C
      [PATCH] More slab.h cleanups · 55935a34
      由 Christoph Lameter 提交于 
      More cleanups for slab.h

1. Remove tabs from weird locations as suggested by Pekka

2. Drop the check for NUMA and SLAB_DEBUG from the fallback section
   as suggested by Pekka.

3. Uses static inline for the fallback defs as also suggested by Pekka.

4. Make kmem_ptr_valid take a const * argument.

5. Separate the NUMA fallback definitions from the kmalloc_track fallback
   definitions.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      55935a34
    • C
      [PATCH] slab: fix sleeping in atomic bug · dd47ea75
      由 Christoph Lameter 提交于 
      Fallback_alloc() does not do the check for GFP_WAIT as done in
cache_grow().  Thus interrupts are disabled when we call kmem_getpages()
which results in the failure.

Duplicate the handling of GFP_WAIT in cache_grow().
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Cc: Jay Cliburn <jacliburn@bellsouth.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      dd47ea75
  23. 11 12月, 2006 1 次提交
  25. 09 12月, 2006 3 次提交