The patch titled
sched: likely profiling
has been removed from the -mm tree. Its filename is
sched-likely-profiling.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: sched: likely profiling
From: Nick Piggin <npiggin@xxxxxxx>
This likely profiling is pretty fun. I found a few possible problems
in sched.c.
This patch may be not measurable, but when I did measure long ago,
nooping (un)likely cost a couple of % on scheduler heavy benchmarks, so
it all adds up.
Tweak some branch hints:
- the 2nd 64 bits in the bitmask is likely to be populated, because it
contains the first 28 bits (nearly 3/4) of the normal priorities.
(ratio of 669669:691 ~= 1000:1).
- it isn't unlikely that context switching switches to another process. it
might be very rapidly switching to and from the idle process (ratio of
475815:419004 and 471330:423544). Let the branch predictor decide.
- preempt_enable seems to be very often called in a nested preempt_disable
or with interrupts disabled (ratio of 3567760:87965 ~= 40:1)
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
Acked-by: Ingo Molnar <mingo@xxxxxxx>
Cc: Daniel Walker <dwalker@xxxxxxxxxx>
Cc: Hua Zhong <hzhong@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/asm-generic/bitops/sched.h | 2 +-
kernel/sched.c | 6 +++---
2 files changed, 4 insertions(+), 4 deletions(-)
diff -puN include/asm-generic/bitops/sched.h~sched-likely-profiling include/asm-generic/bitops/sched.h
--- a/include/asm-generic/bitops/sched.h~sched-likely-profiling
+++ a/include/asm-generic/bitops/sched.h
@@ -15,7 +15,7 @@ static inline int sched_find_first_bit(c
#if BITS_PER_LONG == 64
if (unlikely(b[0]))
return __ffs(b[0]);
- if (unlikely(b[1]))
+ if (likely(b[1]))
return __ffs(b[1]) + 64;
return __ffs(b[2]) + 128;
#elif BITS_PER_LONG == 32
diff -puN kernel/sched.c~sched-likely-profiling kernel/sched.c
--- a/kernel/sched.c~sched-likely-profiling
+++ a/kernel/sched.c
@@ -1822,14 +1822,14 @@ context_switch(struct rq *rq, struct tas
struct mm_struct *mm = next->mm;
struct mm_struct *oldmm = prev->active_mm;
- if (unlikely(!mm)) {
+ if (!mm) {
next->active_mm = oldmm;
atomic_inc(&oldmm->mm_count);
enter_lazy_tlb(oldmm, next);
} else
switch_mm(oldmm, mm, next);
- if (unlikely(!prev->mm)) {
+ if (!prev->mm) {
prev->active_mm = NULL;
WARN_ON(rq->prev_mm);
rq->prev_mm = oldmm;
@@ -3491,7 +3491,7 @@ asmlinkage void __sched preempt_schedule
* If there is a non-zero preempt_count or interrupts are disabled,
* we do not want to preempt the current task. Just return..
*/
- if (unlikely(ti->preempt_count || irqs_disabled()))
+ if (likely(ti->preempt_count || irqs_disabled()))
return;
need_resched:
_
Patches currently in -mm which might be from npiggin@xxxxxxx are
origin.patch
mm-add-arch_alloc_page.patch
radix-tree-rcu-lockless-readside.patch
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