On Fri, Jul 08, 2016 at 10:35:08AM +0100, Mel Gorman wrote: > The vmstat allocstall was fairly useful in the general sense but > node-based LRUs change that. It's important to know if a stall was for an > address-limited allocation request as this will require skipping pages > from other zones. This patch adds pgstall_* counters to replace > allocstall. The sum of the counters will equal the old allocstall so it > can be trivially recalculated. A high number of address-limited > allocation requests may result in a lot of useless LRU scanning for > suitable pages. > > As address-limited allocations require pages to be skipped, it's important > to know how much useless LRU scanning took place so this patch adds > pgskip* counters. This yields the following model > > 1. The number of address-space limited stalls can be accounted for (pgstall) > 2. The amount of useless work required to reclaim the data is accounted > (pgskip) > 3. The total number of scans is available from pgscan_kswapd and pgscan_direct > so from that the ratio of useful to useless scans can be calculated. > > Signed-off-by: Mel Gorman <[email protected]> > Acked-by: Vlastimil Babka <[email protected]>
These statistics should be quite helpful, so: Acked-by: Johannes Weiner <[email protected]> But I have one nitpick: > @@ -23,6 +23,8 @@ > > enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, > FOR_ALL_ZONES(PGALLOC), > + FOR_ALL_ZONES(PGSTALL), > + FOR_ALL_ZONES(PGSCAN_SKIP), > PGFREE, PGACTIVATE, PGDEACTIVATE, > PGFAULT, PGMAJFAULT, > PGLAZYFREED, The PG prefix seems to stand for page, and all stat names that contain it represent some per-page event. PGSTALL is not a page event, though. Would you mind sticking with allocstall? allocstall_dma32 etc.
