Re: Clear performance regression on reaim7 in 2.6.15-git6
From: Martin J. Bligh
Date: Sat Apr 15 2006 - 18:30:26 EST
Andrew Morton wrote:
"Martin J. Bligh" <mbligh@xxxxxxxxxx> wrote:
drilling down into the results directories can get you the command line,
looks like "reaim -f workfile.short -s 1 -e 10 -i 2" to me. Buggered if
I can recall what that did though.
(http://test.kernel.org/abat/20229/004.reaim.test/results/cmdline)
I *think* it's only ia32 NUMA boxes, at least as far as I can see from
a quick poke around. Which would make me guess at scheduler code. Gitweb
would be nice to use, but it doesn't tag the -git snapshots, AFAICS,
which is a real shame. Nor does the git snapshot include the git tag,
as far as I know. Grrrr. I guess I'll download the snapshots and diff
them, and try to pull out the sched changes by hand. Much suckage.
The diffstat for 2.6.15-git5 -> 2.6.15-git6 is at
http://www.zip.com.au/~akpm/linux/patches/stuff/2 - only a single line
changed in sched.c:
diff -uNr 2.6.15-git5/kernel/sched.c 2.6.15-git6/kernel/sched.c
--- 2.6.15-git5/kernel/sched.c 2006-04-15 14:10:43.000000000 -0700
+++ 2.6.15-git6/kernel/sched.c 2006-04-15 14:10:52.000000000 -0700
@@ -4386,6 +4386,7 @@
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
+ mutex_debug_show_all_locks();
}
Hmm. whilst it's probably not that call, it does look like mutex
debugging. Look at the profiles from reaim between -git5 and -git6:
before:
http://test.kernel.org/abat/20115/004.reaim.test/profiling/profile.text
after:
http://test.kernel.org/abat/20229/004.reaim.test/profiling/profile.text
1262 kfree 3.5056
820 mutex_lock_interruptible 164.0000
752 __mutex_lock_slowpath 0.8754
43 schedule 0.0284
35 _spin_lock 2.3333
25 debug_mutex_set_owner 0.1613
23 debug_mutex_add_waiter 0.1586
/me hugs his huge stacks of data.
--------------------------------
config DEBUG_MUTEXES
bool "Mutex debugging, deadlock detection"
default y
depends on DEBUG_KERNEL
help
This allows mutex semantics violations and mutex related deadlocks
(lockups) to be detected and reported automatically.
--------------------------------
Hmmm. Who the hell thought defaulting that to 'y' was a good plan????
It's still broken in 17-rc1 ... will send you a patch in a sec.
M.
PS. Jeff Garzik pointed out there *are* git tags for each -git snapshot
http://www.kernel.org/pub/linux/kernel/v2.6/snapshots/patch-2.6.17-rc1-git11.id
which is really helpful.
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