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

[Jens Axboe <axboe@kernel.dk>]

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.

-- 
Jens Axboe