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SubjectRe: [PATCH] allow PF_MEMALLOC tasks to directly reclaim pages
Marcelo,

Infact, the test can be made even weaker than that.

We only what to avoid the inactive-clean list when allocating from
within an interrupt (or from a bottom-half handler) to avoid
deadlock on taking the pagecache_lock and pagemap_lru_lock.
Note: no allocations are done while holding either of these locks.

Even GFP_ATOMIC doesn't matter; that simply says if we should block or
not (could be an allocation while holding a spinlock, but not inside an
interrupt).

I've been doing v heavy load on a 4-way server with;

if (order == 0 && !in_interrupt())
direct_reclaim = 1;

without any problems.

Of course, the in_interrupt() is heavier than (gfp_mask & __GFP_WAIT),
but the benefits outweight the slight fattening.

Mark



On Fri, 27 Apr 2001, Marcelo Tosatti wrote:

>
> Linus,
>
> Currently __alloc_pages() does not allow PF_MEMALLOC tasks to free clean
> inactive pages.
>
> This is senseless --- if the allocation has __GFP_WAIT set, its ok to grab
> the pagemap_lru_lock/pagecache_lock/etc.
>
> I checked all possible codepaths after reclaim_page() and they are ok.
>
> The following patch fixes that.
>
>
> --- linux/mm/page_alloc.c.orig Fri Apr 27 05:59:35 2001
> +++ linux/mm/page_alloc.c Fri Apr 27 05:59:48 2001
> @@ -295,8 +295,7 @@
> * Can we take pages directly from the inactive_clean
> * list?
> */
> - if (order == 0 && (gfp_mask & __GFP_WAIT) &&
> - !(current->flags & PF_MEMALLOC))
> + if (order == 0 && (gfp_mask & __GFP_WAIT))
> direct_reclaim = 1;
>
> /*
>
>
> -
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