On Fri, May 30, 2025 at 07:52:28PM +1200, Barry Song wrote: > On Fri, May 30, 2025 at 9:14 AM Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > > > On Thu, May 29, 2025 at 04:28:46PM +0100, Matthew Wilcox wrote: > > > Barry's problem is that we're all nervous about possibly regressing > > > performance on some unknown workloads. Just try Barry's proposal, see > > > if anyone actually compains or if we're just afraid of our own shadows. > > > > I actually explained why I think this is a terrible idea. But okay, I > > tried the patch anyway. > > > > This is 'git log' on a hot kernel repo after a large IO stream: > > > > VANILLA BARRY > > Real time 49.93 ( +0.00%) 60.36 ( +20.48%) > > User time 32.10 ( +0.00%) 32.09 ( -0.04%) > > System time 14.41 ( +0.00%) 14.64 ( +1.50%) > > pgmajfault 9227.00 ( +0.00%) 18390.00 ( +99.30%) > > workingset_refault_file 184.00 ( +0.00%) 236899.00 (+127954.05%) > > > > Clearly we can't generally ignore page cache hits just because the > > mmaps() are intermittent. > > Hi Johannes, > Thanks! > > Are you on v1, which lacks folio demotion[1], or v2, which includes it [2]? > > [1] https://lore.kernel.org/linux-mm/20250412085852.48524-1-21cnbao@xxxxxxxxx/ > [2] https://lore.kernel.org/linux-mm/20250514070820.51793-1-21cnbao@xxxxxxxxx/ The subthread is about whether the reference dismissal / demotion should be unconditional (v1) or opt-in (v2). I'm arguing for v2.
