Hi Joonsoo,
On Sat, Jul 07, 2012 at 12:28:41AM +0900, Joonsoo Kim wrote:
> __alloc_pages_direct_compact has many arguments so invoking it is very costly.
It's already slow path so it's pointless for such optimization.
> And in almost invoking case, order is 0, so return immediately.
You can't make sure it.
>
> Let's not invoke it when order 0
Let's not ruin git blame.
>
> Signed-off-by: Joonsoo Kim <js1304@xxxxxxxxx>
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6092f33..f4039aa 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2056,7 +2056,10 @@ out:
> }
>
> #ifdef CONFIG_COMPACTION
> -/* Try memory compaction for high-order allocations before reclaim */
> +/*
> + * Try memory compaction for high-order allocations before reclaim
> + * Must be called with order > 0
> + */
> static struct page *
> __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
> struct zonelist *zonelist, enum zone_type high_zoneidx,
> @@ -2067,8 +2070,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
> {
> struct page *page;
>
> - if (!order)
> - return NULL;
> + BUG_ON(!order);
>
> if (compaction_deferred(preferred_zone, order)) {
> *deferred_compaction = true;
> @@ -2363,15 +2365,17 @@ rebalance:
> * Try direct compaction. The first pass is asynchronous. Subsequent
> * attempts after direct reclaim are synchronous
> */
> - page = __alloc_pages_direct_compact(gfp_mask, order,
> - zonelist, high_zoneidx,
> - nodemask,
> - alloc_flags, preferred_zone,
> - migratetype, sync_migration,
> - &deferred_compaction,
> - &did_some_progress);
> - if (page)
> - goto got_pg;
> + if (unlikely(order)) {
> + page = __alloc_pages_direct_compact(gfp_mask, order,
> + zonelist, high_zoneidx,
> + nodemask,
> + alloc_flags, preferred_zone,
> + migratetype, sync_migration,
> + &deferred_compaction,
> + &did_some_progress);
> + if (page)
> + goto got_pg;
> + }
> sync_migration = true;
>
> /*
> @@ -2446,15 +2450,17 @@ rebalance:
> * direct reclaim and reclaim/compaction depends on compaction
> * being called after reclaim so call directly if necessary
> */
> - page = __alloc_pages_direct_compact(gfp_mask, order,
> - zonelist, high_zoneidx,
> - nodemask,
> - alloc_flags, preferred_zone,
> - migratetype, sync_migration,
> - &deferred_compaction,
> - &did_some_progress);
> - if (page)
> - goto got_pg;
> + if (unlikely(order)) {
> + page = __alloc_pages_direct_compact(gfp_mask, order,
> + zonelist, high_zoneidx,
> + nodemask,
> + alloc_flags, preferred_zone,
> + migratetype, sync_migration,
> + &deferred_compaction,
> + &did_some_progress);
> + if (page)
> + goto got_pg;
> + }
> }
>
> nopage:
> --
> 1.7.9.5
>
> --
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