| Subject | Re: [PATCH 07/25] Check in advance if the zonelist needs additional filtering | From | Pekka Enberg <> | Date | Tue, 21 Apr 2009 10:21:12 +0300 |
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Hi Mel,
On Mon, 2009-04-20 at 23:19 +0100, Mel Gorman wrote: > Zonelist are filtered based on nodemasks for memory policies normally. > It can be additionally filters on cpusets if they exist as well as > noting when zones are full. These simple checks are expensive enough to > be noticed in profiles. This patch checks in advance if zonelist > filtering will ever be needed. If not, then the bulk of the checks are > skipped. > > Signed-off-by: Mel Gorman <mel@csn.ul.ie> > @@ -1401,6 +1405,7 @@ get_page_from_freelist(gfp_t gfp_mask, nodemask_t *nodemask, unsigned int order, > nodemask_t *allowednodes = NULL;/* zonelist_cache approximation */ > int zlc_active = 0; /* set if using zonelist_cache */ > int did_zlc_setup = 0; /* just call zlc_setup() one time */ > + int zonelist_filter = 0; > > (void)first_zones_zonelist(zonelist, high_zoneidx, nodemask, > &preferred_zone); > @@ -1411,6 +1416,10 @@ get_page_from_freelist(gfp_t gfp_mask, nodemask_t *nodemask, unsigned int order, > > VM_BUG_ON(order >= MAX_ORDER); > > + /* Determine in advance if the zonelist needs filtering */ > + if ((alloc_flags & ALLOC_CPUSET) && unlikely(number_of_cpusets > 1)) > + zonelist_filter = 1; > + > zonelist_scan: > /* > * Scan zonelist, looking for a zone with enough free. > @@ -1418,12 +1427,16 @@ zonelist_scan: > */ > for_each_zone_zonelist_nodemask(zone, z, zonelist, > high_zoneidx, nodemask) { > - if (NUMA_BUILD && zlc_active && > - !zlc_zone_worth_trying(zonelist, z, allowednodes)) > - continue; > - if ((alloc_flags & ALLOC_CPUSET) && > - !cpuset_zone_allowed_softwall(zone, gfp_mask)) > - goto try_next_zone; > + > + /* Ignore the additional zonelist filter checks if possible */ > + if (zonelist_filter) { > + if (NUMA_BUILD && zlc_active && > + !zlc_zone_worth_trying(zonelist, z, allowednodes)) > + continue; > + if ((alloc_flags & ALLOC_CPUSET) &&
The above expression is always true here because of the earlier zonelists_filter check, no?
> + !cpuset_zone_allowed_softwall(zone, gfp_mask)) > + goto try_next_zone; > + } > > if (!(alloc_flags & ALLOC_NO_WATERMARKS)) { > unsigned long mark;
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