Re: Performance regressions in 2.6.30-rc7?

[Chris Mason]

On Tue, Jun 09, 2009 at 12:32:08PM +0200, Jan Kara wrote:
> On Thu 04-06-09 21:13:15, Mike Galbraith wrote:
> > On Thu, 2009-06-04 at 13:21 +0200, Jan Kara wrote:
> > 
> > > > Sequential Writes
> > > > 2.6.30-smp-ordered            6000  65536  32   50.16 508.9%    31.996    45595.78   0.64965  0.02402    10
> > > > 2.6.29.4-smp-ordered          6000  65536  32   52.70 543.2%    33.658    23794.92   0.71754  0.00836    10
> > > > 
> > > > 2.6.30-smp-writeback          6000  65536  32   47.82 525.4%    35.003    32588.84   0.56192  0.02298     9
> > > > 2.6.29.4-smp-writeback        6000  65536  32   52.52 467.6%    32.397    12972.78   0.53580  0.00522    11
> > > > 
> > > > 2.6.30-smp-ordered            6000  65536  16   56.08 254.9%    15.463    33000.68   0.39687  0.00521    22
> > > > 2.6.29.4-smp-ordered          6000  65536  16   62.40 308.4%    14.701    13455.02   0.13125  0.00208    20
> > > > 
> > > > 2.6.30-smp-writeback          6000  65536  16   51.90 281.4%    17.098    12869.85   0.36771  0.00104    18
> > > > 2.6.29.4-smp-writeback        6000  65536  16   60.53 272.6%    14.977     8637.08   0.21146  0.00000    22
> > > > 
> > > > 2.6.30-smp-ordered            6000  65536   8   51.09 113.4%     8.700    14856.55   0.06771  0.00417    45
> > > > 2.6.29.4-smp-ordered          6000  65536   8   56.13 130.6%     8.098     8400.45   0.03958  0.00000    43
> > > > 
> > > > 2.6.30-smp-writeback          6000  65536   8   50.19 131.7%     8.680    16821.04   0.11979  0.00208    38
> > > > 2.6.29.4-smp-writeback        6000  65536   8   54.90 130.7%     8.244     4925.48   0.10000  0.00000    42
> > >   It really seems write has some problems... There's consistently lower
> > > throughput and it also seems some writes take really long. I'll try to
> > > reproduce it here.
> > 
> > Looked "pretty solid" to me.  I haven't observed enough to ~trust.
>   OK, I did a few runs of tiobench here and I can confirm that I see about
> 6% performance regression in Sequential Write throughput between 2.6.29
> and 2.6.30-rc8. I'll try to find what's causing it.

My first guess would be the WRITE_SYNC style changes.  Is the regression
still there with noop?

-chris

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