Re: [PATCHSET for-next 0/3] Add FMODE_NOWAIT support to pipes

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On Tue, Mar 07, 2023 at 08:33:24PM -0700, Jens Axboe wrote:
> On 3/7/23 8:10?PM, Jens Axboe wrote:
> > Curious on how big of a difference this makes, I wrote a small benchmark
> > that simply opens 128 pipes and then does 256 rounds of reading and
> > writing to them. This was run 10 times, discarding the first run as it's
> > always a bit slower. Before the patch:
> > 
> > Avg:	262.52 msec
> > Stdev:	  2.12 msec
> > Min:	261.07 msec
> > Max	267.91 msec
> > 
> > and after the patch:
> > 
> > Avg:	24.14 msec
> > Stdev:	 9.61 msec
> > Min:	17.84 msec
> > Max:	43.75 msec
> > 
> > or about a 10x improvement in performance (and efficiency).
> 
> The above test was for a pipe being empty when the read is issued, if
> the test is changed to have data when, then it looks even better:
> 
> Before:
> 
> Avg:	249.24 msec
> Stdev:	  0.20 msec
> Min:	248.96 msec
> Max:	249.53 msec
> 
> After:
> 
> Avg:	 10.86 msec
> Stdev:	  0.91 msec
> Min:	 10.02 msec
> Max:	 12.67 msec
> 
> or about a 23x improvement.

Nice!

Code looks OK, maybe consider s/nonblock/nowait/, but I'm not a pipe
expert so I'll leave nitty gritty details to Al, et al.

Acked-by: Dave Chinner <dchinner@xxxxxxxxxx>
-- 
Dave Chinner
david@xxxxxxxxxxxxx



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