lkml.org 
[lkml]   [2008]   [Mar]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: hackbench regression since 2.6.25-rc
From
Date
On Thu, 2008-03-13 at 01:48 -0700, Andrew Morton wrote:
> On Thu, 13 Mar 2008 15:46:57 +0800 "Zhang, Yanmin" <yanmin_zhang@linux.intel.com> wrote:
>
> > Comparing with 2.6.24, on my 16-core tigerton, hackbench process mode has about
> > 40% regression with 2.6.25-rc1, and more than 20% regression with kernel
> > 2.6.25-rc4, because rc4 includes the reverting patch of scheduler load balance.
> >
> > Command to start it.
> > #hackbench 100 process 2000
> > I ran it for 3 times and sum the values.
> >
> > I tried to investiagte it by bisect.
> > Kernel up to tag 0f4dafc0563c6c49e17fe14b3f5f356e4c4b8806 has the 20% regression.
> > Kernel up to tag 6e90aa972dda8ef86155eefcdbdc8d34165b9f39 hasn't regression.
> >
> > Any bisect between above 2 tags cause kernel hang. I tried to checkout to a point between
> > these 2 tags for many times manually and kernel always paniced.
> >
> > All patches between the 2 tags are on kobject restructure. I guess such restructure
> > creates more cache miss on the 16-core tigerton.
> >
>
> That's pretty surprising - hackbench spends most of its time in userspace
> and zeroing out anonymous pages.
No. vmstat showed hackbench spends almost 100% in sys.

> It shouldn't be fiddling with kobjects
> much at all.
>
> Some kernel profiling might be needed here..
Thanks for your kind reminder. I don't know why I forgot it.

2.6.24 oprofile data:
CPU: Core 2, speed 1602 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
samples % image name app name symbol name
40200494 43.3899 linux-2.6.24 linux-2.6.24 __slab_alloc
35338431 38.1421 linux-2.6.24 linux-2.6.24 add_partial_tail
2993156 3.2306 linux-2.6.24 linux-2.6.24 __slab_free
1365806 1.4742 linux-2.6.24 linux-2.6.24 sock_alloc_send_skb
1253820 1.3533 linux-2.6.24 linux-2.6.24 copy_user_generic_string
1141442 1.2320 linux-2.6.24 linux-2.6.24 unix_stream_recvmsg
846836 0.9140 linux-2.6.24 linux-2.6.24 unix_stream_sendmsg
777561 0.8393 linux-2.6.24 linux-2.6.24 kmem_cache_alloc
587127 0.6337 linux-2.6.24 linux-2.6.24 sock_def_readable




2.6.25-rc4 oprofile data:
CPU: Core 2, speed 1602 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
samples % image name app name symbol name
46746994 43.3801 linux-2.6.25-rc4 linux-2.6.25-rc4 __slab_alloc
45986635 42.6745 linux-2.6.25-rc4 linux-2.6.25-rc4 add_partial
2577578 2.3919 linux-2.6.25-rc4 linux-2.6.25-rc4 __slab_free
1301644 1.2079 linux-2.6.25-rc4 linux-2.6.25-rc4 sock_alloc_send_skb
1185888 1.1005 linux-2.6.25-rc4 linux-2.6.25-rc4 copy_user_generic_string
969847 0.9000 linux-2.6.25-rc4 linux-2.6.25-rc4 unix_stream_recvmsg
806665 0.7486 linux-2.6.25-rc4 linux-2.6.25-rc4 kmem_cache_alloc
731059 0.6784 linux-2.6.25-rc4 linux-2.6.25-rc4 unix_stream_sendmsg


-yanmin




\
 
 \ /
  Last update: 2008-03-13 10:39    [W:0.118 / U:0.328 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site