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Date: Thu, 13 Mar 2008 17:28:58 +0800 From: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com> To: Andrew Morton <akpm@...ux-foundation.org>, Christoph Lameter <clameter@....com> Cc: Kay Sievers <kay.sievers@...y.org>, Greg Kroah-Hartman <gregkh@...e.de>, LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu> Subject: Re: hackbench regression since 2.6.25-rc 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@...ux.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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