From: Helge Deller <deller@gmx.de>
To: James Bottomley <James.Bottomley@HansenPartnership.com>,
Mel Gorman <mgorman@techsingularity.net>,
Mikulas Patocka <mpatocka@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
John David Anglin <dave.anglin@bell.net>,
linux-parisc@vger.kernel.org, linux-mm@kvack.org,
Vlastimil Babka <vbabka@suse.cz>,
Andrea Arcangeli <aarcange@redhat.com>,
Zi Yan <zi.yan@cs.rutgers.edu>
Subject: Re: Memory management broken by "mm: reclaim small amounts of memory when an external fragmentation event occurs"
Date: Mon, 8 Apr 2019 17:22:31 +0200 [thread overview]
Message-ID: <1aca1299-8713-3d54-7c5e-adf791509987@gmx.de> (raw)
In-Reply-To: <1554733749.3137.6.camel@HansenPartnership.com>
On 08.04.19 16:29, James Bottomley wrote:
> On Mon, 2019-04-08 at 10:52 +0100, Mel Gorman wrote:
>> First, if pa-risc is !NUMA then why are separate local ranges
>> represented as separate nodes? Is it because of DISCONTIGMEM or
>> something else? DISCONTIGMEM is before my time so I'm not familiar
>> with it and I consider it "essentially dead" but the arch init code
>> seems to setup pgdats for each physical contiguous range so it's a
>> possibility. The most likely explanation is pa-risc does not have
>> hardware with addressing limitations smaller than the CPUs physical
>> address limits and it's possible to have more ranges than available
>> zones but clarification would be nice.
>
> Let me try, since I remember the ancient history. In the early days,
> there had to be a single mem_map array covering all of physical memory.
> Some pa-risc systems had huge gaps in the physical memory; I think one
> gap was somewhere around 1GB, so this lead us to wasting huge amounts
> of space in mem_map on non-existent memory. What CONFIG_DISCONTIGMEM
> did was allow you to represent this discontinuity on a non-NUMA system
> using numa nodes, so we effectively got one node per discontiguous
> range. It's hacky, but it worked. I thought we finally got converted
> to sparsemem by the NUMA people, but I can't find the commit.
James, you tried once:
https://patchwork.kernel.org/patch/729441/
It seems we better should move over to sparsemem now?
Helge
next prev parent reply other threads:[~2019-04-08 15:22 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-06 15:20 Memory management broken by "mm: reclaim small amounts of memory when an external fragmentation event occurs" Mikulas Patocka
2019-04-06 17:26 ` Mikulas Patocka
2019-04-08 9:52 ` Mel Gorman
2019-04-08 11:10 ` Mikulas Patocka
2019-04-08 12:54 ` Mel Gorman
2019-04-08 14:29 ` James Bottomley
2019-04-08 15:22 ` Helge Deller [this message]
2019-04-08 19:44 ` James Bottomley
2019-04-09 20:09 ` Helge Deller
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=1aca1299-8713-3d54-7c5e-adf791509987@gmx.de \
--to=deller@gmx.de \
--cc=James.Bottomley@HansenPartnership.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=dave.anglin@bell.net \
--cc=linux-mm@kvack.org \
--cc=linux-parisc@vger.kernel.org \
--cc=mgorman@techsingularity.net \
--cc=mpatocka@redhat.com \
--cc=vbabka@suse.cz \
--cc=zi.yan@cs.rutgers.edu \
/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).