Re: mmap()/VM problems in 2.4.0

Vlad Bolkhovitine (vladb@sw.com.sg)
Tue, 16 Jan 2001 14:43:01 +0800


Mike Galbraith wrote:
>
> On 15 Jan 2001, Zlatko Calusic wrote:
>
> > "Vlad Bolkhovitine" <vladb@sw.com.sg> writes:
> >
> > > Here is updated info for 2.4.1pre3:
> > >
> > > Size is MB, BlkSz is Bytes, Read, Write, and Seeks are MB/sec
> > >
> > > with mmap()
> > >
> > > File Block Num Seq Read Rand Read Seq Write Rand Write
> > > Dir Size Size Thr Rate (CPU%) Rate (CPU%) Rate (CPU%) Rate (CPU%)
> > > ------- ------ ------- --- ----------- ----------- ----------- -----------
> > > . 1024 4096 2 1.089 1.24% 0.235 0.45% 1.118 4.11% 0.616 1.41%
> > >
[...]
> > > Mmap() performance dropped dramatically down to almost unusable level. Plus,
> > > system was unusable during test: "vmstat 1" updated results every 1-2 _MINUTES_!
> > >
> >
> > You need Marcelo's patch. Please apply and retest.
>
> My box thinks quite highly of that patch fwiw, but insists that he needs
> to apply Jens Axboes' blk patch first ;-) (Not because of tiobench)

New data:

2.4.1pre3 + Marcelo's patch

File Block Num Seq Read Rand Read Seq Write Rand Write
Dir Size Size Thr Rate (CPU%) Rate (CPU%) Rate (CPU%) Rate (CPU%)
------- ------ ------- --- ----------- ----------- ----------- -----------
. 1024 4096 2 12.68 9.23% 0.497 0.92% 10.57 15.3% 0.594 1.44%

The same performance level as for 2.4.0. No improvement.

2.4.1pre3 + Marcelo's patch + Jens Axboes' blk-13B patch

File Block Num Seq Read Rand Read Seq Write Rand Write
Dir Size Size Thr Rate (CPU%) Rate (CPU%) Rate (CPU%) Rate (CPU%)
------- ------ ------- --- ----------- ----------- ----------- -----------
. 1024 4096 2 12.47 10.0% 0.504 1.13% 9.998 16.5% 0.735 2.21%

No significant difference, just noise. IMHO, it is expected, since 2 threads
simply aren't enough to launch blk patch's mechanisms

> -Mike
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