From: Simon Jeons <simon.jeons@gmail.com>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Petr Holasek <pholasek@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Izik Eidus <izik.eidus@ravellosystems.com>,
Rik van Riel <riel@redhat.com>,
David Rientjes <rientjes@google.com>,
Anton Arapov <anton@redhat.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 1/11] ksm: allow trees per NUMA node
Date: Sat, 26 Jan 2013 21:16:21 -0600 [thread overview]
Message-ID: <1359256581.4159.16.camel@kernel> (raw)
In-Reply-To: <alpine.LNX.2.00.1301261826000.7411@eggly.anvils>
On Sat, 2013-01-26 at 18:54 -0800, Hugh Dickins wrote:
> On Sat, 26 Jan 2013, Simon Jeons wrote:
> > On Fri, 2013-01-25 at 17:54 -0800, Hugh Dickins wrote:
> > > From: Petr Holasek <pholasek@redhat.com>
> > > @@ -1122,6 +1166,18 @@ struct rmap_item *unstable_tree_search_i
> > > return NULL;
> > > }
> > >
> > > + /*
> > > + * If tree_page has been migrated to another NUMA node, it
> > > + * will be flushed out and put into the right unstable tree
> >
> > Then why not insert the new page to unstable tree during page migration
> > against current upstream? Because default behavior is merge across
> > nodes.
>
> I don't understand the words "against current upstream" in your question.
I mean current upstream codes without numa awareness. :)
>
> We cannot move a page (strictly, a node) from one tree to another during
> page migration itself, because the necessary ksm_thread_mutex is not held.
> Not would we even want to while "merge across nodes".
>
> Ah, perhaps you are pointing out that in current upstream, the only user
> of ksm page migration is memory hotremove, which in current upstream does
> hold ksm_thread_mutex.
>
> So you'd like us to add code for moving a node from one tree to another
> in ksm_migrate_page() (and what would it do when it collides with an
Without numa awareness, I still can't understand your explanation why
can't insert the node to the tree just after page migration instead of
inserting it at the next scan.
> existing node?), code which will then be removed a few patches later
> when ksm page migration is fully enabled?
>
> No, I'm not going to put any more thought into that. When Andrea pointed
> out the problem with Petr's original change to ksm_migrate_page(), I did
> indeed think that we could do something cleverer at that point; but once
> I got down to trying it, found that a dead end. I wasn't going to be
> able to test the hotremove case properly anyway, so no good pursuing
> solutions that couldn't be generalized.
>
> Hugh
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next prev parent reply other threads:[~2013-01-27 3:16 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-26 1:53 [PATCH 0/11] ksm: NUMA trees and page migration Hugh Dickins
2013-01-26 1:54 ` [PATCH 1/11] ksm: allow trees per NUMA node Hugh Dickins
2013-01-27 1:14 ` Simon Jeons
2013-01-27 2:54 ` Hugh Dickins
2013-01-27 3:16 ` Simon Jeons [this message]
2013-01-27 21:55 ` Hugh Dickins
2013-01-28 23:03 ` Andrew Morton
2013-01-29 1:17 ` Hugh Dickins
2013-01-28 23:08 ` Andrew Morton
2013-01-29 1:38 ` Hugh Dickins
2013-02-05 16:41 ` Mel Gorman
2013-02-07 23:57 ` Hugh Dickins
2013-01-26 1:56 ` [PATCH 2/11] ksm: add sysfs ABI Documentation Hugh Dickins
2013-01-26 1:58 ` [PATCH 3/11] ksm: trivial tidyups Hugh Dickins
2013-01-28 23:11 ` Andrew Morton
2013-01-29 1:44 ` Hugh Dickins
2013-01-26 1:59 ` [PATCH 4/11] ksm: reorganize ksm_check_stable_tree Hugh Dickins
2013-02-05 16:48 ` Mel Gorman
2013-02-08 0:07 ` Hugh Dickins
2013-02-14 11:30 ` Mel Gorman
2013-01-26 2:00 ` [PATCH 5/11] ksm: get_ksm_page locked Hugh Dickins
2013-01-27 2:36 ` Simon Jeons
2013-01-27 22:08 ` Hugh Dickins
2013-01-28 0:36 ` Simon Jeons
2013-01-28 3:35 ` Hugh Dickins
2013-01-27 2:48 ` Simon Jeons
2013-01-27 22:10 ` Hugh Dickins
2013-02-05 17:18 ` Mel Gorman
2013-02-08 0:33 ` Hugh Dickins
2013-02-14 11:34 ` Mel Gorman
2013-01-26 2:01 ` [PATCH 6/11] ksm: remove old stable nodes more thoroughly Hugh Dickins
2013-01-27 4:55 ` Simon Jeons
2013-01-27 23:05 ` Hugh Dickins
2013-01-28 1:42 ` Simon Jeons
2013-01-28 4:14 ` Hugh Dickins
2013-01-28 2:12 ` Simon Jeons
2013-01-28 4:19 ` Hugh Dickins
2013-01-28 6:36 ` Simon Jeons
2013-01-28 23:44 ` Andrew Morton
2013-01-29 2:03 ` Hugh Dickins
2013-02-05 17:55 ` Mel Gorman
2013-02-08 19:33 ` Hugh Dickins
2013-02-14 11:58 ` Mel Gorman
2013-02-14 22:19 ` Hugh Dickins
2013-01-26 2:03 ` [PATCH 7/11] ksm: make KSM page migration possible Hugh Dickins
2013-01-27 5:47 ` Simon Jeons
2013-01-27 23:12 ` Hugh Dickins
2013-01-28 0:41 ` Simon Jeons
2013-01-28 3:44 ` Hugh Dickins
2013-02-05 19:11 ` Mel Gorman
2013-02-08 20:52 ` Hugh Dickins
2013-01-26 2:05 ` [PATCH 8/11] ksm: make !merge_across_nodes migration safe Hugh Dickins
2013-01-27 8:49 ` Simon Jeons
2013-01-27 23:25 ` Hugh Dickins
2013-01-28 3:44 ` Simon Jeons
2013-01-26 2:06 ` [PATCH 9/11] ksm: enable KSM page migration Hugh Dickins
2013-01-26 2:07 ` [PATCH 10/11] mm: remove offlining arg to migrate_pages Hugh Dickins
2013-01-26 2:10 ` [PATCH 11/11] ksm: stop hotremove lockdep warning Hugh Dickins
2013-01-27 6:23 ` Simon Jeons
2013-01-27 23:35 ` Hugh Dickins
2013-02-08 18:45 ` Gerald Schaefer
2013-02-11 22:13 ` Hugh Dickins
2013-01-28 23:54 ` [PATCH 0/11] ksm: NUMA trees and page migration Andrew Morton
2013-01-29 0:49 ` Izik Eidus
2013-01-29 2:26 ` Izik Eidus
2013-01-29 16:51 ` Andrea Arcangeli
2013-01-31 0:05 ` Ric Mason
2013-01-29 1:07 ` Hugh Dickins
2013-01-29 10:45 ` Gleb Natapov
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