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Date: Fri, 4 May 2007 13:42:12 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Christoph Lameter <clameter@....com> Cc: linux-kernel@...r.kernel.org Subject: Re: Remove constructor from buffer_head On Thu, 3 May 2007 20:08:41 -0700 (PDT) Christoph Lameter <clameter@....com> wrote: > Performance tests show a slight improvements in netperf (not a > strong case for a performance improvement but removing the > constructor has definitely no negative impact so why keep > this around?). > > TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to localhost (127.0.0.1) port 0 AF_INET > Recv Send Send > Socket Socket Message Elapsed > Size Size Size Time Throughput > bytes bytes bytes secs. 10^6bits/sec > > Before: > 87380 16384 16384 10.01 6026.04 > 87380 16384 16384 10.01 5992.17 > 87380 16384 16384 10.01 6071.23 > > After: > 87380 16384 16384 10.01 6090.20 > 87380 16384 16384 10.01 6078.3 > 87380 16384 16384 10.00 6013.52 > > > Signed-off-by: Christoph Lameter <clameter@....com> > > --- > fs/buffer.c | 22 ++++------------------ So I benchmarked this by repeatedly extending (via write()) and truncating a 10MB file, on ext2. Using create-delete.c from http://www.zip.com.au/~akpm/linux/patches/stuff/ext3-tools.tar.gz Machine is a fast 2x4 core Woodcrest. CONFIG_SLAB=y The command used was time create-delete -s $((16 * 1024 * 1024)) -n 300 foo which will allocate and free 300*4096 buffer_heads. With patch: akpm2:/mnt/sda2> time create-delete -s $((16 * 1024 * 1024)) -n 300 foo create-delete -s $((16 * 1024 * 1024)) -n 300 foo 0.00s user 4.56s system 99% cpu 4.565 total akpm2:/mnt/sda2> time create-delete -s $((16 * 1024 * 1024)) -n 300 foo create-delete -s $((16 * 1024 * 1024)) -n 300 foo 0.00s user 4.60s system 99% cpu 4.612 total akpm2:/mnt/sda2> time create-delete -s $((16 * 1024 * 1024)) -n 300 foo create-delete -s $((16 * 1024 * 1024)) -n 300 foo 0.00s user 4.60s system 99% cpu 4.602 total akpm2:/mnt/sda2> time create-delete -s $((16 * 1024 * 1024)) -n 300 foo create-delete -s $((16 * 1024 * 1024)) -n 300 foo 0.00s user 4.56s system 99% cpu 4.567 total akpm2:/mnt/sda2> time create-delete -s $((16 * 1024 * 1024)) -n 300 foo create-delete -s $((16 * 1024 * 1024)) -n 300 foo 0.00s user 4.59s system 95% cpu 4.824 total Without patch: akpm2:/mnt/sda2> time create-delete -s $((16 * 1024 * 1024)) -n 300 foo create-delete -s $((16 * 1024 * 1024)) -n 300 foo 0.00s user 4.42s system 99% cpu 4.419 total akpm2:/mnt/sda2> time create-delete -s $((16 * 1024 * 1024)) -n 300 foo create-delete -s $((16 * 1024 * 1024)) -n 300 foo 0.00s user 4.42s system 99% cpu 4.421 total akpm2:/mnt/sda2> time create-delete -s $((16 * 1024 * 1024)) -n 300 foo create-delete -s $((16 * 1024 * 1024)) -n 300 foo 0.00s user 4.42s system 99% cpu 4.427 total akpm2:/mnt/sda2> time create-delete -s $((16 * 1024 * 1024)) -n 300 foo create-delete -s $((16 * 1024 * 1024)) -n 300 foo 0.00s user 4.42s system 99% cpu 4.417 total akpm2:/mnt/sda2> time create-delete -s $((16 * 1024 * 1024)) -n 300 foo create-delete -s $((16 * 1024 * 1024)) -n 300 foo 0.00s user 4.42s system 99% cpu 4.435 total So the patch took the average system time from 4.42 seconds up to 4.582 seconds. Nice slowdown! It could just be the usual inter-kernel-build noise, dunno. I'd investigate further, but someone has gone and broken oprofile. - 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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