Re: iozone regression with 2.6.29-rc6

Lin Ming
2009-03-02T03:21:24Z

On Mon, 2009-03-02 at 11:12 +0800, Wu, Fengguang wrote:
> On Mon, Mar 02, 2009 at 10:19:04AM +0800, Lin, Ming wrote:
> > On Fri, 2009-02-27 at 17:49 +0800, Peter Zijlstra wrote:
> > > On Fri, 2009-02-27 at 17:13 +0800, Lin Ming wrote:
> > > > bisect locates below commits,
> > > >
> > > > commit 1cf6e7d83bf334cc5916137862c920a97aabc018
> > > > Author: Nick Piggin <npiggin@suse.de>
> > > > Date: Wed Feb 18 14:48:18 2009 -0800
> > > >
> > > > mm: task dirty accounting fix
> > > >
> > > > YAMAMOTO-san noticed that task_dirty_inc doesn't seem to be called properly for
> > > > cases where set_page_dirty is not used to dirty a page (eg. mark_buffer_dirty).
> > > >
> > > > Additionally, there is some inconsistency about when task_dirty_inc is
> > > > called. It is used for dirty balancing, however it even gets called for
> > > > __set_page_dirty_no_writeback.
> > > >
> > > > So rather than increment it in a set_page_dirty wrapper, move it down to
> > > > exactly where the dirty page accounting stats are incremented.
> > > >
> > > > Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
> > > > Signed-off-by: Nick Piggin <npiggin@suse.de>
> > > > Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> > > > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > > > Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> > > >
> > > >
> > > > below data in parenthesis is the result after above commit reverted, for example,
> > > > -10% (+2%) means,
> > > > iozone has ~10% regression with 2.6.29-rc6 compared with 2.6.29-rc5.
> > > > and
> > > > iozone has ~2% improvement with 2.6.29-rc6-revert-1cf6e7d compared with 2.6.29-rc5.
> > > >
> > > >
> > > > 4P dual-core HT 2P qual-core 2P qual-core HT
> > > > tulsa stockley Nehalem
> > > > --------------------------------------------------------
> > > > iozone-rewrite -10% (+2%) -8% (0%) -10% (-7%)
> > > > iozone-rand-write -50% (0%) -20% (+10%)
> > > > iozone-read -13% (0%)
> > > > iozone-write -28% (-1%)
> > > > iozone-reread -5% (-1%)
> > > > iozone-mmap-read -7% (+2%)
> > > > iozone-mmap-reread -7% (+2%)
> > > > iozone-mmap-rand-read -7% (+3%)
> > > > iozone-mmap-rand-write -5% (0%)
> > >
> > > Ugh, that's unexpected..
> > >
> > > So 'better' accounting leads to worse performance, which would indicate
> > > we throttle more.
> > >
> > > I take it you machine has gobs of memory.
> > >
> > > Does something like the below help any?
> >
> > It helps some as below test result,
> > The data in second parenthesis means 2.6.29-rc6-with-peter's-patch
> > compared with 2.6.29-rc5.
> >
> > 4P dual-core HT 2P qual-core 2P qual-core HT
> > tulsa stockley Nehalem
> > --------------------------------------------------------
> > iozone-rewrite -10% (+2%)(-3%) -8% (0%)(0%) -10% (-7%)(-2%)
> > iozone-rand-write -50% (0%)(-10%) -20% (+10%)(+3%)
> > iozone-read -13% (0%)(-8%)
> > iozone-write -28% (-1%)(+35%)
> > iozone-reread -5% (-1%)(-1%)
> > iozone-mmap-read -7% (+2%)(-7%)
> > iozone-mmap-reread -7% (+2%)(-7%)
> > iozone-mmap-rand-read -7% (+3%)(-7%)
> > iozone-mmap-rand-write -5% (0%)(+27%)
>
> Thanks, Lin Ming. To better understand the situation, would you please
> provide the iozone command and memory info about the servers?

iozone -i 0 -i 1 -i 2 -i 3 -i 4 -r 4k -s 64k -s 512m -s 1200m -b tmp.xls
iozone -B -r 4k -s 64k -s 512m -s 1200m -b tmp.xls

4P dual-core HT tulsa /proc/meminfo
------------------------------------
MemTotal: 8189476 kB
MemFree: 7915884 kB
Buffers: 32676 kB
Cached: 139784 kB
SwapCached: 0 kB
Active: 35852 kB
Inactive: 145564 kB
Active(anon): 9048 kB
Inactive(anon): 0 kB
Active(file): 26804 kB
Inactive(file): 145564 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 140 kB
Writeback: 0 kB
AnonPages: 9068 kB
Mapped: 4084 kB
Slab: 31180 kB
SReclaimable: 14800 kB
SUnreclaim: 16380 kB
PageTables: 1236 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 4094736 kB
Committed_AS: 18446744073709545248 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 286416 kB
VmallocChunk: 34359449467 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 4096 kB
DirectMap2M: 8380416

2P qual-core stockley /proc/meminfo
-----------------------------------
MemTotal: 8167260 kB
MemFree: 7951068 kB
Buffers: 30988 kB
Cached: 123772 kB
SwapCached: 0 kB
Active: 34744 kB
Inactive: 129296 kB
Active(anon): 9412 kB
Inactive(anon): 0 kB
Active(file): 25332 kB
Inactive(file): 129296 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 272 kB
Writeback: 0 kB
AnonPages: 9408 kB
Mapped: 4072 kB
Slab: 21760 kB
SReclaimable: 10612 kB
SUnreclaim: 11148 kB
PageTables: 1260 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 4083628 kB
Committed_AS: 18446744073709540996 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 11216 kB
VmallocChunk: 34359726459 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 7168 kB
DirectMap2M: 8380416 kB

2P qual-core HT Nehalem /proc/meminfo
-------------------------------------
MemTotal: 6113044 kB
MemFree: 5947476 kB
Buffers: 17056 kB
Cached: 44280 kB
SwapCached: 0 kB
Active: 31268 kB
Inactive: 40300 kB
Active(anon): 10308 kB
Inactive(anon): 0 kB
Active(file): 20960 kB
Inactive(file): 40300 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 280 kB
Writeback: 0 kB
AnonPages: 10328 kB
Mapped: 5096 kB
Slab: 27844 kB
SReclaimable: 10988 kB
SUnreclaim: 16856 kB
PageTables: 2204 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 3056520 kB
Committed_AS: 18446744073709542732 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 286428 kB
VmallocChunk: 34359451259 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 8192 kB
DirectMap2M: 6275072 kB

Lin Ming

>
> Thanks,
> Fengguang