linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "Martin J. Bligh" <mbligh@aracnet.com>
To: William Lee Irwin III <wli@holomorphy.com>,
	Andrew Morton <akpm@digeo.com>
Cc: Dave Hansen <haveblue@us.ibm.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	colpatch@us.ibm.com
Subject: Re: [PATCH] per-zone kswapd process
Date: Thu, 12 Sep 2002 22:10:37 -0700	[thread overview]
Message-ID: <617478427.1031868636@[10.10.2.3]> (raw)
In-Reply-To: <20020913045938.GG2179@holomorphy.com>

>> Also, I'm wondering why the individual kernel threads don't have
>> their affinity masks set to make them run on the CPUs to which the
>> zone (or zones) are local?
>> Isn't it the case that with this code you could end up with a kswapd
>> on node 0 crunching on node 1's pages while a kswapd on node 1 crunches
>> on node 0's pages?
> 
> Without some architecture-neutral method of topology detection, there's
> no way to do this. A follow-up when it's there should fix it.

Every discontigmem arch should implement cpu_to_node, with a generic
fallback mechanism that returns 0 or something. Not that we do right
now, but that's easy to fix. There should also be a node_to_cpus call
that returns a bitmask of which cpus are in that node.

Matt ... want to sneak in the first bit of the topology patch, or
whatever lump this fell under? Seems like an appropriate juncture.
We have the code already somewhere, just need to fish it out.

>> If I'm not totally out to lunch on this, I'd have thought that a
>> better approach would be
>> 	int sys_kswapd(int nid)
>> 	{
>> 		return kernel_thread(kswapd, ...);
>> 	}
>> Userspace could then set up the CPU affinity based on some topology
>> or config information and would then parent a kswapd instance.  That
>> kswapd instance would then be bound to the CPUs which were on the
>> node identified by `nid'.
>> Or something like that?
> 
> I'm very very scared of handing things like that to userspace, largely
> because I don't trust userspace at all.
> 
> At this point, we need to enumerate nodes and provide a cpu to node
> correspondence to userspace, and the kernel can obey, aside from the
> question of "What do we do if we need to scan a node without a kswapd
> started yet?". I think mbligh recently got the long-needed arch code in
> for cpu to node... But I'm just not able to make the leap of faith that
> memory detection is something that can ever comfortably be given to
> userspace.

I don't think the userspace stuff is necessary - we can do this all 
in the kernel dead easily I think. Just need a couple of definitions,
which are trivially small functions.

M.


  reply	other threads:[~2002-09-13  5:08 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-09-13  3:33 Dave Hansen
2002-09-13  4:06 ` Andrew Morton
2002-09-13  4:59   ` William Lee Irwin III
2002-09-13  5:10     ` Martin J. Bligh [this message]
     [not found]       ` <3D8232DE.9090000@us.ibm.com>
     [not found]         ` <3D823702.8E29AB4F@digeo.com>
     [not found]           ` <3D8251D6.3060704@us.ibm.com>
     [not found]             ` <3D82566B.EB2939D5@digeo.com>
2002-09-13 22:52               ` [PATCH] per-zone^Wnode " Dave Hansen
2002-09-13 23:24                 ` Matthew Dobson
2002-09-13 23:29                 ` Matthew Dobson
2002-09-13 23:46                 ` William Lee Irwin III
2002-09-14  0:02                   ` Andrew Morton
2002-09-14  0:12                     ` William Lee Irwin III
2002-09-14  1:19                       ` Andrew Morton
2002-09-13  5:46     ` [PATCH] per-zone " Andrew Morton
2002-09-13  5:38       ` Martin J. Bligh
2002-09-13  6:03         ` Andrew Morton
2002-09-13 13:05     ` Alan Cox
2002-09-13 21:30       ` William Lee Irwin III
2002-09-18 16:07         ` [PATCH] recognize MAP_LOCKED in mmap() call Hubertus Franke
2002-09-18 16:29           ` Andrew Morton
2002-09-16  5:44     ` [PATCH] per-zone kswapd process Daniel Phillips
2002-09-16  7:46       ` William Lee Irwin III
2002-09-16 15:12         ` Rik van Riel

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='617478427.1031868636@[10.10.2.3]' \
    --to=mbligh@aracnet.com \
    --cc=akpm@digeo.com \
    --cc=colpatch@us.ibm.com \
    --cc=haveblue@us.ibm.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=wli@holomorphy.com \
    --subject='Re: [PATCH] per-zone kswapd process' \
    /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

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).