On Mon, 8 Nov 2021 10:57:23 -0500 Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > Hi Andrew, > > I promised to give this patch some more testing exposure while it sits > in -mm. We've been steadily rolling this version of the change to our > fleet over the last months and it's currently on 20% of FB servers. We > have not noticed crashes or performance regressions because of it. > (The other 80% is running a previous version of the patch.) > > The comment in 'series' says "extra cycle" but that was 5.15 :-) Do > you think we can get it merged into 5.16? > > Just to reiterate, without the patch, there is very broad production > breakage for FB beyond reduced cache effectiveness. Yes, we lose cache > pages prematurely. But a bigger problem is that we lose nonresident > info we store in the inodes. This defeats thrash detection, which in > turn defeats psi and central reclaim deciscion making. The downstream > effects of this are quite severe and widespread: > > - memory prioity inversion between containers > - failure to offload cold memory to swap with proactive reclaim > - breakdown of container health monitoring and userspace OOM killing > > I'm not exaggerating when I say we can't reliably operate our fleet > without this patch. We've had to carry variants of it for two years > now. It'd be great to get this fixed upstream. Cool, thanks for the update. I'll sent it Linuswards this week.
