On Mon, Jan 23, 2023 at 11:17:53AM -0500, Jeff Moyer wrote: > Jeff Moyer <jmoyer@xxxxxxxxxx> writes: > > > Hi, Kent, > > > > Kent Overstreet <kent.overstreet@xxxxxxxxx> writes: > > > >> I've been observing workloads where IPIs due to wakeups in > >> aio_complete() are ~15% of total CPU time in the profile. Most of those > >> wakeups are unnecessary when completion batching is in use in > >> io_getevents(). > >> > >> This plumbs min_nr through via the wait eventry, so that aio_complete() > >> can avoid doing unnecessary wakeups. > >> > >> v2: This fixes a race in the first version of the patch. If we read some > >> events out after adding to the waitlist, we need to update wait.min_nr > >> call prepare_to_wait_event() again before scheduling. > > > > I like the idea of the patch, and I'll get some real world performance > > numbers soon. But first, this version (and the previous version as > > well) fails test case 23 in the libaio regression test suite: > > > > Starting cases/23.p > > FAIL: poll missed an event! > > FAIL: poll missed an event! > > test cases/23.t completed FAILED. > > It turns out that this only fails on the (relatively) old kernel against > which I applied the patches. When I apply both patches to the latest > tree, there is no test failure. > > Sorry for the noise, I'll be sure to test on the latest going forward. > Now to figure out what changed elsewhere to fix this.... That's odd - let me know if you'd like me to take a look...
