From: Vlastimil Babka <vbabka@suse.cz>
To: Joonsoo Kim <js1304@gmail.com>
Cc: Rik van Riel <riel@surriel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Memory Management List <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-team@fb.com, Roman Gushchin <guro@fb.com>,
Qian Cai <cai@lca.pw>, Mel Gorman <mgorman@techsingularity.net>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH] mm,page_alloc,cma: conditionally prefer cma pageblocks for movable allocations
Date: Wed, 11 Mar 2020 18:41:38 +0100 [thread overview]
Message-ID: <89865b7b-f0ed-999d-0f23-4dbfb45115db@suse.cz> (raw)
In-Reply-To: <CAAmzW4P6+3O_RLvgy_QOKD4iXw+Hk3HE7Toc4Ky7kvQbCozCeA@mail.gmail.com>
On 3/11/20 11:13 AM, Joonsoo Kim wrote:
>>
>> Few years ago Joonsoo wanted to fix these kinds of weird MIGRATE_CMA corner
>> cases by using ZONE_MOVABLE instead [1]. Unfortunately it was reverted due to
>> unresolved bugs. Perhaps the idea could be resurrected now?
>>
>> [1]
>> https://lore.kernel.org/linux-mm/1512114786-5085-1-git-send-email-iamjoonsoo.kim@lge.com/
>
> Thanks for ccing, Vlastimil.
No problem. Also, welcome back :)
> Recently, I'm working for resurrecting this idea.
> I will send the preparation patches in this or next week.
Good to hear!
> Unresolved bugs of my patchset comes from the fact that ZONE_MOVABLE
> which is used for
> serving CMA memory in my patchset could have both lowmem(direct mapped) and
> highmem(no direct mapped) pages on CONFIG_HIGHMEM enabled system.
>
> For someone to use this memory, PageHighMem() should be called to
> check if there is direct
> mapping or not. Current PageHighMem() implementation is:
>
> #define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
>
> Since ZONE_MOVABLE has both typed pages, ZONE_MOVABLE should be considered
> as highmem zone. In this case, PageHighMem() always returns TRUE for
> all pages on
> ZONE_MOVABLE and lowmem pages on ZONE_MOVABLE could make some troubles.
Doh, HighMem brings only troubles these days [1].
[1] https://lwn.net/Articles/813201/
> My plan to fix this problem is to change the PageHighMem() implementation.
>
> #define PageHighMem(__p) (page_to_pfn(__p) >= max_low_pfn)
>
> In fact, PageHighMem() is used to check whether direct mapping exists or not.
> With this new implementation, regardless of the zone type of the page, we can
> correctly check if the page is direct mapped or not. Changing the
> name, PageHighMem(),
> to !PageDirectMapped() is also planned but it will be done after
> everything have settle down.
>
> Unfortunately, before changing the implementation, I should check the
> all call-sites
> of PageHighMem() since there is some callers who use PageHighMem() to check
> the zone type.
>
> What my preparation patch will does is to correct this PageHighMem() usage.
> After fixing it, I will try to merge the patchset [1].
>
> Thanks.
>
next prev parent reply other threads:[~2020-03-11 17:41 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-06 20:01 [PATCH] mm,page_alloc,cma: conditionally prefer cma pageblocks for movable allocations Rik van Riel
2020-03-07 22:38 ` Andrew Morton
2020-03-08 13:23 ` Rik van Riel
2020-03-11 17:58 ` Vlastimil Babka
2020-03-11 22:58 ` Roman Gushchin
2020-03-11 23:03 ` Vlastimil Babka
2020-03-11 23:21 ` Roman Gushchin
2020-03-11 8:51 ` Vlastimil Babka
2020-03-11 10:13 ` Joonsoo Kim
2020-03-11 17:41 ` Vlastimil Babka [this message]
2020-03-11 17:35 ` Roman Gushchin
2020-03-12 1:41 ` Joonsoo Kim
2020-03-12 2:39 ` Roman Gushchin
2020-03-12 8:56 ` Joonsoo Kim
2020-03-12 17:07 ` Roman Gushchin
2020-03-13 7:44 ` Joonsoo Kim
2020-04-02 2:13 ` Andrew Morton
2020-04-02 2:53 ` Roman Gushchin
2020-04-02 5:43 ` Joonsoo Kim
2020-04-02 19:42 ` Roman Gushchin
2020-04-03 4:34 ` Joonsoo Kim
2020-04-03 17:50 ` Roman Gushchin
2020-04-02 3:05 ` Roman Gushchin
2020-03-21 0:49 ` Minchan Kim
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=89865b7b-f0ed-999d-0f23-4dbfb45115db@suse.cz \
--to=vbabka@suse.cz \
--cc=akpm@linux-foundation.org \
--cc=anshuman.khandual@arm.com \
--cc=cai@lca.pw \
--cc=guro@fb.com \
--cc=iamjoonsoo.kim@lge.com \
--cc=js1304@gmail.com \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
--cc=riel@surriel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).