From: Mel Gorman <mgorman@techsingularity.net>
To: Michal Hocko <mhocko@suse.com>
Cc: Linux-MM <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
NeilBrown <neilb@suse.de>,
Thierry Reding <thierry.reding@gmail.com>,
Matthew Wilcox <willy@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 5/7] mm/page_alloc.c: Allow __GFP_NOFAIL requests deeper access to reserves
Date: Thu, 12 Jan 2023 09:43:41 +0000 [thread overview]
Message-ID: <20230112094341.hom3ccscbko6v626@techsingularity.net> (raw)
In-Reply-To: <Y77ZxWRYe+4RPGRj@dhcp22.suse.cz>
On Wed, Jan 11, 2023 at 04:46:13PM +0100, Michal Hocko wrote:
> On Mon 09-01-23 15:16:29, Mel Gorman wrote:
> > Currently __GFP_NOFAIL allocations without any other flags can access 25%
> > of the reserves but these requests imply that the system cannot make forward
> > progress until the allocation succeeds. Allow __GFP_NOFAIL access to 75%
> > of the min reserve.
>
> I am not sure this is really needed. IIRC the original motivation for
> allowing NOFAIL request to access access to memory reserves was
> GFP_NOFS|__GFP_NOFAIL requests which do not invoke the OOM killer.
> The amount of memory reserves granted was not really important. The
> point was to allow to move forward. Giving more of the reserves is a
> double edge sword. It can help in some cases but it can also prevent
> other high priority users from fwd progress.
>
> I would much rahter see such a change with an example where it really
> made a difference.
>
Fair point but based on your review for "mm/page_alloc: Give GFP_ATOMIC
and non-blocking allocations access to reserves" and only allowing
non-blocking allocations to access reserves if __GFP_HIGH is also
specified, this patch becomes a no-op and can be dropped.
If GFP_NOFAIL requests really require deeper access to reserves, it'll
have to be explicitly handled in __zone_watermark_ok and __GFP_NOFAIL
would be added to the ALLOC_RESERVES collection of flags.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2023-01-12 9:43 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-09 15:16 [PATCH 0/6 v2] Discard __GFP_ATOMIC Mel Gorman
2023-01-09 15:16 ` [PATCH 1/7] mm/page_alloc: Rename ALLOC_HIGH to ALLOC_MIN_RESERVE Mel Gorman
2023-01-11 15:18 ` Michal Hocko
2023-01-12 9:26 ` Mel Gorman
2023-01-09 15:16 ` [PATCH 2/7] mm/page_alloc: Treat RT tasks similar to __GFP_HIGH Mel Gorman
2023-01-11 15:27 ` Michal Hocko
2023-01-12 9:36 ` Mel Gorman
2023-01-12 9:47 ` Michal Hocko
2023-01-12 16:42 ` Mel Gorman
2023-01-13 9:04 ` David Laight
2023-01-13 11:09 ` Mel Gorman
2023-01-09 15:16 ` [PATCH 3/7] mm/page_alloc: Explicitly record high-order atomic allocations in alloc_flags Mel Gorman
2023-01-10 15:28 ` Vlastimil Babka
2023-01-11 15:36 ` Michal Hocko
2023-01-12 9:38 ` Mel Gorman
2023-01-09 15:16 ` [PATCH 4/7] mm/page_alloc: Explicitly define what alloc flags deplete min reserves Mel Gorman
2023-01-11 14:04 ` Vlastimil Babka
2023-01-11 15:37 ` Michal Hocko
2023-01-09 15:16 ` [PATCH 5/7] mm/page_alloc.c: Allow __GFP_NOFAIL requests deeper access to reserves Mel Gorman
2023-01-11 14:05 ` Vlastimil Babka
2023-01-11 15:46 ` Michal Hocko
2023-01-12 9:43 ` Mel Gorman [this message]
2023-01-09 15:16 ` [PATCH 6/7] mm/page_alloc: Give GFP_ATOMIC and non-blocking allocations " Mel Gorman
2023-01-11 14:12 ` Vlastimil Babka
2023-01-11 15:58 ` Michal Hocko
2023-01-11 17:05 ` Mel Gorman
2023-01-12 8:11 ` Michal Hocko
2023-01-12 8:29 ` Michal Hocko
2023-01-12 9:24 ` Mel Gorman
2023-01-12 9:45 ` Michal Hocko
2023-01-14 22:10 ` NeilBrown
2023-01-16 10:29 ` Mel Gorman
2023-01-09 15:16 ` [PATCH 7/7] mm: discard __GFP_ATOMIC Mel Gorman
2023-01-12 8:12 ` Michal Hocko
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