Re: [PATCH -next RFC v3 0/8] improve tag allocation under heavy load

[yukuai (C)]

在 2022/04/25 19:20, Damien Le Moal 写道:
> On 4/25/22 16:28, yukuai (C) wrote:
> > 在 2022/04/25 15:06, Damien Le Moal 写道:
> >
> > > > > By the way, did you check that doing something like:
> > > > >
> > > > > echo 2048 > /sys/block/sdX/queue/nr_requests
> > > > >
> > > > > improves performance for your high number of jobs test case ?
> > > >
> > > > Yes, performance will not degrade when numjobs is not greater than 256
> > > > in this case.
> > >
> > > That is my thinking as well. I am asking if did check that (did you run it ?).
> >
> > Hi,
> >
> > I'm sure I ran it with 256 jobs before.
> >
> > However, I didn't run it with 512 jobs. And following is the result I
> > just tested:
>
> What was nr_requests ? The default 64 ?
> If you increase that number, do you see better throughput/more requests
> being sequential ?

Sorry if I didn't explain this clearly.

If nr_requests is 64, numjobs is 512, the ratio of sequential is about
20%. If nr_requests is 2048, numjobs is 512, the ratio is 49.1%.

Then yes, increase nr_requests can improve performance in the test case.

> > ratio of sequential io: 49.1%
> >
> > Read|Write seek
> >
> > cnt 99338, zero cnt 48753
> >
> >       >=(KB) .. <(KB)     : count       ratio |distribution
> >                |
> >            0 .. 1         : 48753       49.1%
> > |########################################|
> >            1 .. 2         : 0            0.0% |
> >                |
> >            2 .. 4         : 0            0.0% |
> >                |
> >            4 .. 8         : 0            0.0% |
> >                |
> >            8 .. 16        : 0            0.0% |
> >                |
> >           16 .. 32        : 0            0.0% |
> >                |
> >           32 .. 64        : 0            0.0% |
> >                |
> >           64 .. 128       : 4975         5.0% |#####
> >                |
> >          128 .. 256       : 4439         4.5% |####
> >                |
> >          256 .. 512       : 2615         2.6% |###
> >                |
> >          512 .. 1024      : 967          1.0% |#
> >                |
> >         1024 .. 2048      : 213          0.2% |#
> >                |
> >         2048 .. 4096      : 375          0.4% |#
> >                |
> >         4096 .. 8192      : 723          0.7% |#
> >                |
> >         8192 .. 16384     : 1436         1.4% |##
> >                |
> >        16384 .. 32768     : 2626         2.6% |###
> >                |
> >        32768 .. 65536     : 4197         4.2% |####
> >                |
> >        65536 .. 131072    : 6431         6.5% |######
> >                |
> >       131072 .. 262144    : 7590         7.6% |#######
> >                |
> >       262144 .. 524288    : 6433         6.5% |######
> >                |
> >       524288 .. 1048576   : 4583         4.6% |####
> >                |
> >      1048576 .. 2097152   : 2237         2.3% |##
> >                |
> >      2097152 .. 4194304   : 489          0.5% |#
> >                |
> >      4194304 .. 8388608   : 83           0.1% |#
> >                |
> >      8388608 .. 16777216  : 36           0.0% |#
> >                |
> >     16777216 .. 33554432  : 0            0.0% |
> >                |
> >     33554432 .. 67108864  : 0            0.0% |
> >                |
> >     67108864 .. 134217728 : 137          0.1% |#
> >                |