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  1. 05 3月, 2009 2 次提交
    • F
      sched: don't rebalance if attached on NULL domain · 8a0be9ef
      由 Frederic Weisbecker 提交于 
      Impact: fix function graph trace hang / drop pointless softirq on UP

While debugging a function graph trace hang on an old PII, I saw
that it consumed most of its time on the timer interrupt. And
the domain rebalancing softirq was the most concerned.

The timer interrupt calls trigger_load_balance() which will
decide if it is worth to schedule a rebalancing softirq.

In case of builtin UP kernel, no problem arises because there is
no domain question.

In case of builtin SMP kernel running on an SMP box, still no
problem, the softirq will be raised each time we reach the
next_balance time.

In case of builtin SMP kernel running on a UP box (most distros
provide default SMP kernels, whatever the box you have), then
the CPU is attached to the NULL sched domain. So a kind of
unexpected behaviour happen:

trigger_load_balance() -> raises the rebalancing softirq later
on softirq: run_rebalance_domains() -> rebalance_domains() where
the for_each_domain(cpu, sd) is not taken because of the NULL
domain we are attached at. Which means rq->next_balance is never
updated. So on the next timer tick, we will enter
trigger_load_balance() which will always reschedule() the
rebalacing softirq:

if (time_after_eq(jiffies, rq->next_balance))
	raise_softirq(SCHED_SOFTIRQ);

So for each tick, we process this pointless softirq.

This patch fixes it by checking if we are attached to the null
domain before raising the softirq, another possible fix would be
to set the maximal possible JIFFIES value to rq->next_balance if
we are attached to the NULL domain.

v2: build fix on UP
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <49af242d.1c07d00a.32d5.ffffc019@mx.google.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      8a0be9ef
    • I
      Merge commit 'v2.6.29-rc7' into sched/core · 49d2d266
      由 Ingo Molnar 提交于
      49d2d266
  3. 04 3月, 2009 9 次提交
  5. 03 3月, 2009 24 次提交
  7. 02 3月, 2009 5 次提交
    • I
      Merge branches 'sched/clock', 'sched/urgent' and 'linus' into sched/core · 5512b3ec
      由 Ingo Molnar 提交于
      5512b3ec
    • P
      x86 mmiotrace: fix race with release_kmmio_fault_page() · 340430c5
      由 Pekka Paalanen 提交于 
      There was a theoretical possibility to a race between arming a page in
post_kmmio_handler() and disarming the page in
release_kmmio_fault_page():

cpu0                             cpu1
------------------------------------------------------------------
mmiotrace shutdown
enter release_kmmio_fault_page
                                 fault on the page
                                 disarm the page
disarm the page
                                 handle the MMIO access
                                 re-arm the page
put the page on release list
remove_kmmio_fault_pages()
                                 fault on the page
                                 page not known to mmiotrace
                                 fall back to do_page_fault()
                                 *KABOOM*

(This scenario also shows the double disarm case which is allowed.)

Fixed by acquiring kmmio_lock in post_kmmio_handler() and checking
if the page is being released from mmiotrace.
Signed-off-by: NPekka Paalanen <pq@iki.fi>
Cc: Stuart Bennett <stuart@freedesktop.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      340430c5
    • S
      x86 mmiotrace: improve handling of secondary faults · 3e39aa15
      由 Stuart Bennett 提交于 
      Upgrade some kmmio.c debug messages to warnings.
Allow secondary faults on probed pages to fall through, and only log
secondary faults that are not due to non-present pages.

Patch edited by Pekka Paalanen.
Signed-off-by: NStuart Bennett <stuart@freedesktop.org>
Signed-off-by: NPekka Paalanen <pq@iki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      3e39aa15
    • P
      x86 mmiotrace: split set_page_presence() · 0b700a6a
      由 Pekka Paalanen 提交于 
      From 36772dcb6ffbbb68254cbfc379a103acd2fbfefc Mon Sep 17 00:00:00 2001
From: Pekka Paalanen <pq@iki.fi>
Date: Sat, 28 Feb 2009 21:34:59 +0200

Split set_page_presence() in kmmio.c into two more functions set_pmd_presence()
and set_pte_presence(). Purely code reorganization, no functional changes.
Signed-off-by: NPekka Paalanen <pq@iki.fi>
Cc: Stuart Bennett <stuart@freedesktop.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      0b700a6a
    • P
      x86 mmiotrace: fix save/restore page table state · 5359b585
      由 Pekka Paalanen 提交于 
      From baa99e2b32449ec7bf147c234adfa444caecac8a Mon Sep 17 00:00:00 2001
From: Pekka Paalanen <pq@iki.fi>
Date: Sun, 22 Feb 2009 20:02:43 +0200

Blindly setting _PAGE_PRESENT in disarm_kmmio_fault_page() overlooks the
possibility, that the page was not present when it was armed.

Make arm_kmmio_fault_page() store the previous page presence in struct
kmmio_fault_page and use it on disarm.

This patch was originally written by Stuart Bennett, but Pekka Paalanen
rewrote it a little different.
Signed-off-by: NPekka Paalanen <pq@iki.fi>
Cc: Stuart Bennett <stuart@freedesktop.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      5359b585