Messages in this thread | | | Date | Fri, 2 Nov 2018 09:55:57 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH RFC] mm: do not start node_reclaim for page order > MAX_ORDER |
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On Thu 01-11-18 20:37:52, Konstantin Khlebnikov wrote: > Page allocator has check in __alloc_pages_slowpath() but nowdays > there is earlier entry point into reclimer without such check: > get_page_from_freelist() -> node_reclaim().
Is the order check so expensive that it would be visible in the fast path? Spreading these MAX_ORDER checks sounds quite fragile to me.
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> > --- > mm/vmscan.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 62ac0c488624..52f672420f0b 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -4117,6 +4117,12 @@ int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) > { > int ret; > > + /* > + * Do not scan if allocation will never succeed. > + */ > + if (order >= MAX_ORDER) > + return NODE_RECLAIM_NOSCAN; > + > /* > * Node reclaim reclaims unmapped file backed pages and > * slab pages if we are over the defined limits. >
-- Michal Hocko SUSE Labs
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