lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 29 Mar 2017 17:49:57 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        David Rientjes <rientjes@...gle.com>, kernel-team@...com,
        kernel-team@....com
Subject: Re: [PATCH v3 4/8] mm, page_alloc: count movable pages when stealing
 from pageblock

On 03/16/2017 02:53 AM, Joonsoo Kim wrote:
> On Tue, Mar 07, 2017 at 02:15:41PM +0100, Vlastimil Babka wrote:
>> When stealing pages from pageblock of a different migratetype, we count how
>> many free pages were stolen, and change the pageblock's migratetype if more
>> than half of the pageblock was free. This might be too conservative, as there
>> might be other pages that are not free, but were allocated with the same
>> migratetype as our allocation requested.
> 
> I think that too conservative is good for movable case. In my experiments,
> fragmentation spreads out when unmovable/reclaimable pageblock is
> changed to movable pageblock prematurely ('prematurely' means that
> allocated unmovable pages remains). As you said below, movable allocations
> falling back to other pageblocks don't causes permanent fragmentation.
> Therefore, we don't need to be less conservative for movable
> allocation. So, how about following change to keep the criteria for
> movable allocation conservative even with this counting improvement?
> 
> threshold = (1 << (pageblock_order - 1));
> if (start_type == MIGRATE_MOVABLE)
>         threshold += (1 << (pageblock_order - 2));
> 
> if (free_pages + alike_pages >= threshold)
>         ...

That could help, or also not. Keeping more pageblocks marked as unmovable also
means that more unmovable allocations will spread out to them all, even if they
would fit within less pageblocks. MIGRATE_MIXED was an idea to help in this
case, as truly unmovable pageblocks would be preferred to the mixed ones.

Can't decide about such change without testing :/

> Thanks.
> 

Powered by blists - more mailing lists