* Re: [PATCH] mm: delete duplicate order checking, when stealing whole pageblock
[not found] <20210611063834.11871-1-chengkaitao@didiglobal.com>
@ 2021-06-12 0:00 ` Andrew Morton
0 siblings, 0 replies; only message in thread
From: Andrew Morton @ 2021-06-12 0:00 UTC (permalink / raw)
To: chengkaitao; +Cc: linux-mm, linux-kernel, smcdef, Joonsoo Kim
On Fri, 11 Jun 2021 14:38:34 +0800 chengkaitao <pilgrimtao@gmail.com> wrote:
> From: chengkaitao <pilgrimtao@gmail.com>
>
> 1. Already has (order >= pageblock_order / 2) here, we don't neet
> (order >= pageblock_order)
> 2. set function can_steal_fallback to inline
>
> ...
>
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2619,18 +2619,8 @@ static void change_pageblock_range(struct page *pageblock_page,
> * is worse than movable allocations stealing from unmovable and reclaimable
> * pageblocks.
> */
> -static bool can_steal_fallback(unsigned int order, int start_mt)
> +static inline bool can_steal_fallback(unsigned int order, int start_mt)
> {
> - /*
> - * Leaving this order check is intended, although there is
> - * relaxed order check in next check. The reason is that
> - * we can actually steal whole pageblock if this condition met,
> - * but, below check doesn't guarantee it and that is just heuristic
> - * so could be changed anytime.
> - */
> - if (order >= pageblock_order)
> - return true;
> -
> if (order >= pageblock_order / 2 ||
> start_mt == MIGRATE_RECLAIMABLE ||
> start_mt == MIGRATE_UNMOVABLE ||
Well, that redundant check was put there deliberately, as the comment
explains.
The reasoning is perhaps a little dubious, but it seems that the
compiler has optimized away the redundant check anyway (your patch
doesn't alter code size).
^ permalink raw reply [flat|nested] only message in thread