From: Michal Hocko <mhocko@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
linux-mm@kvack.org, akpm@linux-foundation.org,
iamjoonsoo.kim@lge.com, riel@redhat.com, rientjes@google.com,
mgorman@techsingularity.net, hannes@cmpxchg.org,
linux-kernel@vger.kernel.org, torvalds@linux-foundation.org
Subject: Re: [RFC 02/13] mm, page_alloc: set alloc_flags only once in slowpath
Date: Thu, 12 May 2016 14:41:41 +0200 [thread overview]
Message-ID: <20160512124141.GH4200@dhcp22.suse.cz> (raw)
In-Reply-To: <5731D453.8050104@suse.cz>
On Tue 10-05-16 14:30:11, Vlastimil Babka wrote:
[...]
> >From 68f09f1d4381c7451238b4575557580380d8bf30 Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@suse.cz>
> Date: Fri, 29 Apr 2016 11:51:17 +0200
> Subject: [RFC 02/13] mm, page_alloc: set alloc_flags only once in slowpath
>
> In __alloc_pages_slowpath(), alloc_flags doesn't change after it's initialized,
> so move the initialization above the retry: label. Also make the comment above
> the initialization more descriptive.
>
> The only exception in the alloc_flags being constant is ALLOC_NO_WATERMARKS,
> which may change due to TIF_MEMDIE being set on the allocating thread. We can
> fix this, and make the code simpler and a bit more effective at the same time,
> by moving the part that determines ALLOC_NO_WATERMARKS from
> gfp_to_alloc_flags() to gfp_pfmemalloc_allowed(). This means we don't have to
> mask out ALLOC_NO_WATERMARKS in several places in __alloc_pages_slowpath()
> anymore. The only test for the flag can instead call gfp_pfmemalloc_allowed().
I like this _very_ much! gfp_to_alloc_flags was really ugly doing two
separate things and it is nice to split them up and give the whole thing
more sense. gfp_pfmemalloc_allowed() is the bright example of it.
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/page_alloc.c | 49 ++++++++++++++++++++++++-------------------------
> 1 file changed, 24 insertions(+), 25 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a50184ec6ca0..1b58facf4b5e 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3216,8 +3216,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
> */
> count_vm_event(COMPACTSTALL);
>
> - page = get_page_from_freelist(gfp_mask, order,
> - alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
> + page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
>
> if (page) {
> struct zone *zone = page_zone(page);
> @@ -3366,8 +3365,7 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
> return NULL;
>
> retry:
> - page = get_page_from_freelist(gfp_mask, order,
> - alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
> + page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
>
> /*
> * If an allocation failed after direct reclaim, it could be because
> @@ -3425,16 +3423,6 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
> } else if (unlikely(rt_task(current)) && !in_interrupt())
> alloc_flags |= ALLOC_HARDER;
>
> - if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
> - if (gfp_mask & __GFP_MEMALLOC)
> - alloc_flags |= ALLOC_NO_WATERMARKS;
> - else if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
> - alloc_flags |= ALLOC_NO_WATERMARKS;
> - else if (!in_interrupt() &&
> - ((current->flags & PF_MEMALLOC) ||
> - unlikely(test_thread_flag(TIF_MEMDIE))))
> - alloc_flags |= ALLOC_NO_WATERMARKS;
> - }
> #ifdef CONFIG_CMA
> if (gfpflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
> alloc_flags |= ALLOC_CMA;
> @@ -3444,7 +3432,19 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
>
> bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
> {
> - return !!(gfp_to_alloc_flags(gfp_mask) & ALLOC_NO_WATERMARKS);
> + if (unlikely(gfp_mask & __GFP_NOMEMALLOC))
> + return false;
> +
> + if (gfp_mask & __GFP_MEMALLOC)
> + return true;
> + if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
> + return true;
> + if (!in_interrupt() &&
> + ((current->flags & PF_MEMALLOC) ||
> + unlikely(test_thread_flag(TIF_MEMDIE))))
> + return true;
> +
> + return false;
> }
>
> static inline bool is_thp_gfp_mask(gfp_t gfp_mask)
> @@ -3579,25 +3579,24 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
> gfp_mask &= ~__GFP_ATOMIC;
>
> -retry:
> - if (gfp_mask & __GFP_KSWAPD_RECLAIM)
> - wake_all_kswapds(order, ac);
> -
> /*
> - * OK, we're below the kswapd watermark and have kicked background
> - * reclaim. Now things get more complex, so set up alloc_flags according
> - * to how we want to proceed.
> + * The fast path uses conservative alloc_flags to succeed only until
> + * kswapd needs to be woken up, and to avoid the cost of setting up
> + * alloc_flags precisely. So we do that now.
> */
> alloc_flags = gfp_to_alloc_flags(gfp_mask);
>
> +retry:
> + if (gfp_mask & __GFP_KSWAPD_RECLAIM)
> + wake_all_kswapds(order, ac);
> +
> /* This is the last chance, in general, before the goto nopage. */
> - page = get_page_from_freelist(gfp_mask, order,
> - alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
> + page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
> if (page)
> goto got_pg;
>
> /* Allocate without watermarks if the context allows */
> - if (alloc_flags & ALLOC_NO_WATERMARKS) {
> + if (gfp_pfmemalloc_allowed(gfp_mask)) {
> /*
> * Ignore mempolicies if ALLOC_NO_WATERMARKS on the grounds
> * the allocation is high priority and these type of
> --
> 2.8.2
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-05-12 12:41 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-10 7:35 [RFC 00/13] make direct compaction more deterministic Vlastimil Babka
2016-05-10 7:35 ` [RFC 01/13] mm, compaction: don't isolate PageWriteback pages in MIGRATE_SYNC_LIGHT mode Vlastimil Babka
2016-05-11 12:40 ` Michal Hocko
2016-05-10 7:35 ` [RFC 02/13] mm, page_alloc: set alloc_flags only once in slowpath Vlastimil Babka
2016-05-10 11:28 ` Tetsuo Handa
2016-05-10 12:30 ` Vlastimil Babka
2016-05-12 12:41 ` Michal Hocko [this message]
2016-05-31 6:20 ` Joonsoo Kim
2016-05-31 7:59 ` Vlastimil Babka
2016-06-02 1:50 ` Joonsoo Kim
2016-05-10 7:35 ` [RFC 03/13] mm, page_alloc: don't retry initial attempt " Vlastimil Babka
2016-05-12 12:48 ` Michal Hocko
2016-05-31 6:25 ` Joonsoo Kim
2016-05-31 12:03 ` Vlastimil Babka
2016-05-10 7:35 ` [RFC 04/13] mm, page_alloc: restructure direct compaction handling " Vlastimil Babka
2016-05-12 13:29 ` Michal Hocko
2016-05-13 8:10 ` Vlastimil Babka
2016-05-13 8:31 ` Michal Hocko
2016-05-10 7:35 ` [RFC 05/13] mm, page_alloc: make THP-specific decisions more generic Vlastimil Babka
2016-05-12 13:43 ` Michal Hocko
2016-05-10 7:35 ` [RFC 06/13] mm, thp: remove __GFP_NORETRY from khugepaged and madvised allocations Vlastimil Babka
2016-05-12 16:20 ` Michal Hocko
2016-05-13 8:23 ` Vlastimil Babka
2016-05-13 12:05 ` Michal Hocko
2016-05-18 11:59 ` Vlastimil Babka
2016-05-18 15:24 ` Michal Hocko
2016-05-20 13:57 ` Vlastimil Babka
2016-05-23 8:39 ` Michal Hocko
2016-05-10 7:35 ` [RFC 07/13] mm, compaction: introduce direct compaction priority Vlastimil Babka
2016-05-13 12:37 ` Michal Hocko
2016-05-10 7:35 ` [RFC 08/13] mm, compaction: simplify contended compaction handling Vlastimil Babka
2016-05-13 13:09 ` Michal Hocko
2016-05-16 7:10 ` Vlastimil Babka
2016-05-10 7:35 ` [RFC 09/13] mm, compaction: make whole_zone flag ignore cached scanner positions Vlastimil Babka
2016-05-13 13:23 ` Michal Hocko
2016-05-10 7:36 ` [RFC 10/13] mm, compaction: cleanup unused functions Vlastimil Babka
2016-05-10 7:36 ` [RFC 11/13] mm, compaction: add the ultimate direct compaction priority Vlastimil Babka
2016-05-13 13:38 ` Michal Hocko
2016-05-16 7:17 ` Vlastimil Babka
2016-05-16 8:11 ` Michal Hocko
2016-05-18 12:46 ` Vlastimil Babka
2016-05-10 7:36 ` [RFC 12/13] mm, compaction: more reliably increase " Vlastimil Babka
2016-05-10 12:55 ` Vlastimil Babka
2016-05-13 14:15 ` Michal Hocko
2016-05-16 7:31 ` Vlastimil Babka
2016-05-16 8:14 ` Michal Hocko
2016-05-16 9:27 ` Vlastimil Babka
2016-05-16 9:52 ` Michal Hocko
2016-05-31 6:37 ` Joonsoo Kim
2016-05-31 12:07 ` Vlastimil Babka
2016-05-31 12:29 ` Vlastimil Babka
2016-06-02 2:50 ` Joonsoo Kim
2016-05-10 7:36 ` [RFC 13/13] mm, compaction: fix and improve watermark handling Vlastimil Babka
2016-05-16 9:25 ` Michal Hocko
2016-05-16 9:50 ` Vlastimil Babka
2016-05-16 12:30 ` Michal Hocko
2016-05-18 13:50 ` Mel Gorman
2016-05-18 14:27 ` Michal Hocko
2016-05-18 14:40 ` Mel Gorman
2016-05-17 20:01 ` [RFC 00/13] make direct compaction more deterministic Michal Hocko
2016-05-18 7:19 ` Vlastimil Babka
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