On Wed, Aug 17, 2022 at 02:59:48AM +0000, CGEL wrote: > On Wed, Aug 03, 2022 at 09:55:39AM -0400, Johannes Weiner wrote: > > On Mon, Aug 01, 2022 at 12:42:04AM +0000, cgel.zte@xxxxxxxxx wrote: > > > > This doubles the psi cache footprint on every context switch, wakeup, > > sleep, etc. in the scheduler. You're also adding more branches to > > those same paths. It'll measurably affect everybody who is using psi. > > > > Yet, in the years of using psi in production myself, I've never felt > > the need for what this patch provides. There are event counters for > > everything that contributes to pressure, and it's never been hard to > > rootcause spikes. There are also things like bpftrace that let you > > identify who is stalling for how long in order to do one-off tuning > > and systems introspection. > > > We think this patch is not for rootcause spikes, it's for automatic optimize > memory besides oomd, especially for sysctl adjustment. For example if we see > much pressure of direct reclaim the automatic optimize program might turn up > watermark_scale_factor. > The base idea is that this patch gives user a brief UI to know what kind of > memory pressure the system is suffering, and to optimize the system in a fine > grain. It could provide data for user to adjust watermark_boost_factor, > extfrag_threshold, compaction_proactiveness,transparent_hugepage/defrag, > swappiness, vfs_cache_pressure, madvise(), which may not easy for to do > before. > > It's not easy for automatic optimize program to use tools likes bpftrace or > ftrace to do this. > > While we may use CONFIG_PSI_XX or bootparam to turn on/off this patch to avoid > additional footprint for user who not need this. Hi Do you think this is praciseable?
