On 25.11.2015 18:42, Vladimir Davydov wrote: > The comment to shrink_slab states that the portion of kmem objects > scanned by it equals the portion of lru pages scanned by shrink_zone > over shrinker->seeks. > > shrinker->seeks is supposed to be equal to the number of disk seeks > required to recreated an object. It is usually set to DEFAULT_SEEKS (2), > which is quite logical, because most kmem objects (e.g. dentry or inode) > require random IO to reread (seek to read and seek back). > > That said, one would expect that dcache is scanned two times less > intensively than page cache, which sounds sane as dentries are generally > more costly to recreate. > > However, the formula for distributing memory pressure between slab and > lru actually looks as follows (see do_shrink_slab): > > lru_scanned > objs_to_scan = objs_total * --------------- * 4 / shrinker->seeks > lru_reclaimable > > That is dcache, as well as most of other slab caches, is scanned two > times more aggressively than page cache. > > Fix this by dropping '4' from the equation above. > > Signed-off-by: Vladimir Davydov <[email protected]>
For [1]-[3]: Reviewed-by: Kirill Tkhai <[email protected]> > --- > mm/vmscan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 9b1c73bb465c..eadc08b7a5d6 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -262,7 +262,7 @@ static unsigned long do_shrink_slab(struct shrink_control > *shrinkctl, > nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0); > > total_scan = nr; > - delta = (4 * nr_scanned) / shrinker->seeks; > + delta = nr_scanned / shrinker->seeks; > delta *= max_pass; > do_div(delta, nr_eligible + 1); > total_scan += delta; > _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
