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* 12aceb89b0bc eventfd: convert to f_op->read_iter() causes 6.7% performance regression
@ 2021-04-14 11:23 Hao Xu
  0 siblings, 0 replies; only message in thread
From: Hao Xu @ 2021-04-14 11:23 UTC (permalink / raw)
  To: Jens Axboe; +Cc: io-uring, Alexander Viro

Hi Jens,
We found that 12aceb89b0bc eventfd: convert to f_op->read_iter()
introduced 6.7% peformance regression in test suite will-it-scale

The test commands are:
./runtest.py eventfd1 10 thread 1
and
./runtest.py eventfd1 10 thread 128

the test is a simple while which is like:
while(time not over) {
   write(eventfd);
   read(eventfd);
}

By perf analysis, I saw that the main cost is new_sync_read().
Though I think this regression only happens when there is no
'schedule/sleep'(otherwise sleep occupies most time), I feel it
still necessary to report it.



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2021-04-14 11:23 12aceb89b0bc eventfd: convert to f_op->read_iter() causes 6.7% performance regression Hao Xu

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