On 30 Jan 2019, at 20:34, Dave Chinner wrote: > On Wed, Jan 30, 2019 at 12:21:07PM +0000, Chris Mason wrote: >> >> >> On 29 Jan 2019, at 23:17, Dave Chinner wrote: >> >>> From: Dave Chinner <dchinner@xxxxxxxxxx> >>> >>> This reverts commit a76cf1a474d7dbcd9336b5f5afb0162baa142cf0. >>> >>> This change causes serious changes to page cache and inode cache >>> behaviour and balance, resulting in major performance regressions >>> when combining worklaods such as large file copies and kernel >>> compiles. >>> >>> https://bugzilla.kernel.org/show_bug.cgi?id=202441 >> >> I'm a little confused by the latest comment in the bz: >> >> https://bugzilla.kernel.org/show_bug.cgi?id=202441#c24 > > Which says the first patch that changed the shrinker behaviour is > the underlying cause of the regression. > >> Are these reverts sufficient? > > I think so. Based on the latest comment: "If I had been less strict in my testing I probably would have discovered that the problem was present earlier than 4.19.3. Mr Gushins commit made it more visible. I'm going back to work after two days off, so I might not be able to respond inside your working hours, but I'll keep checking in on this as I get a chance." I don't think the reverts are sufficient. > >> Roman beat me to suggesting Rik's followup. We hit a different >> problem >> in prod with small slabs, and have a lot of instrumentation on Rik's >> code helping. > > I think that's just another nasty, expedient hack that doesn't solve > the underlying problem. Solving the underlying problem does not > require changing core reclaim algorithms and upsetting a page > reclaim/shrinker balance that has been stable and worked well for > just about everyone for years. > Things are definitely breaking down in non-specialized workloads, and have been for a long time. -chris
