Am 14.02.2020 um 21:49 schrieb Tyler Sanderson <tysand@xxxxxxxxxx>:
Regarding Wei's patch that modifies the shrinker implementation, versus this patch which reverts to OOM notifier: I am in favor of both patches. But I do want to make sure a fix gets back ported to 4.19 where the performance regression was first introduced. My concern with reverting to the OOM notifier is, as mst@ put it (in the other thread):
"when linux hits OOM all kind of error paths are being hit, latent bugs start triggering, latency goes up drastically."
Yeah, and that was the default behavior for years, so it‘s not big news :)
The guest could be in a lot of pain before the OOM notifier is invoked, and it seems like the shrinker API might allow more fine grained control of when we deflate.
On the other hand, I'm not totally convinced that Wei's patch is an expected use of the shrinker/page-cache APIs, and maybe it is fragile. Needs more testing and scrutiny.
It seems to me like the shrinker API is the right API in the long run, perhaps with some fixes and modifications. But maybe reverting to OOM notifier is the best patch to back
I think that‘s a good idea. Revert to the old state we had for years and then implement a proper, fully tested solution (e.g., shrinkers with priorities).
Cheers! |
