linux-kernel - Re: Generic approach to customizable zones - was: Re: [PATCH v7 0/7] Introduce ZONE

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 28 Apr 2017 10:36:28 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Igor Stoppa <igor.stoppa@...wei.com>
Cc:     Joonsoo Kim <js1304@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        mgorman@...hsingularity.net, Laura Abbott <lauraa@...eaurora.org>,
        Minchan Kim <minchan@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Michal Nazarewicz <mina86@...a86.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Russell King <linux@...linux.org.uk>,
        Will Deacon <will.deacon@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@....com
Subject: Re: Generic approach to customizable zones - was: Re: [PATCH v7 0/7]
 Introduce ZONE_CMA

I didn't read this thoughly yet because I will be travelling shortly but
this point alone just made ask, because it seems there is some
misunderstanding

On Fri 28-04-17 11:04:27, Igor Stoppa wrote:
[...]
> * if one is happy to have a 64bits type, allow for as many zones as
>   it's possible to fit, or anyway more than what is possible with
>   the 32 bit mask.

zones are currently placed in struct page::flags. And that already is
64b size on 64b arches. And we do not really have any room spare there.
We encode page flags, zone id, numa_nid/sparse section_nr there. How can
you add more without enlarging the struct page itself or using external
means to store the same information (page_ext comes to mind)? Even if
the later would be possible then note thatpage_zone() is used in many
performance sensitive paths and making it perform well with special
casing would be far from trivial.
-- 
Michal Hocko
SUSE Labs