From: Herbert Poetzl <herbert@13thfloor.at>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Kirill Korotaev <dev@sw.ru>,
containers@lists.osdl.org, hansendc@us.ibm.com,
linux-kernel@vger.kernel.org, devel@openvz.org
Subject: Re: [Devel] Re: [RFC][PATCH 2/7] RSS controller core
Date: Tue, 13 Mar 2007 15:59:38 +0100 [thread overview]
Message-ID: <20070313145938.GG8755@MAIL.13thfloor.at> (raw)
In-Reply-To: <20070313034834.14013bb0.akpm@linux-foundation.org>
On Tue, Mar 13, 2007 at 03:48:34AM -0800, Andrew Morton wrote:
> > On Tue, 13 Mar 2007 13:19:53 +0300 Kirill Korotaev <dev@sw.ru> wrote:
> > Andrew Morton wrote:
> > >>>> - shared mappings of 'shared' files (binaries
> > >>>> and libraries) to allow for reduced memory
> > >>>> footprint when N identical guests are running
> > >>>
> > >>>So, it sounds like this can be phrased as a requirement like:
> > >>>
> > >>> "Guests must be able to share pages."
> > >>>
> > >>>Can you give us an idea why this is so?
> > >>
> > >>sure, one reason for this is that guests tend to
> > >>be similar (or almost identical) which results
> > >>in quite a lot of 'shared' libraries and executables
> > >>which would otherwise get cached for each guest and
> > >>would also be mapped for each guest separately
> > >
> > > nooooooo. What you're saying there amounts to text replication.
> > > There is no proposal here to create duplicated copies of pagecache
> > > pages: the VM just doesn't support that (Nick has soe protopatches
> > > which do this as a possible NUMA optimisation).
> > >
> > > So these mmapped pages will contiue to be shared across all
> > > guests. The problem boils down to "which guest(s) get charged for
> > > each shared page".
> > >
> > > A simple and obvious and easy-to-implement answer is "the guest
> > > which paged it in". I think we should firstly explain why that is
> > > insufficient.
> > I guess by "paged it in" you essentially mean
> > "mapped the page into address space for the *first* time"?
>
> Not really - I mean "first allocated the page". ie: major fault(),
> read(), write(), etc.
>
> > i.e. how many times the same page mapped into 2 address spaces
> > in the same container should be accounted for?
> >
> > We believe ONE. It is better due to:
> > - it allows better estimate how much RAM container uses.
> > - if one container mapped a single page 10,000 times,
> > it doesn't mean it is worse than a container which mapped only 200
> > pages and that it should be killed in case of OOM.
>
> I'm not sure that we need to account for pages at all, nor care about
> rss.
>
> If we use a physical zone-based containment scheme: fake-numa,
> variable-sized zones, etc then it all becomes moot.
sounds good to me, just not sure it provides what we
need, but I'm sure I'll figure that with your help ...
> You set up a container which has 1.5GB of physial memory then toss
> processes into it. As that process set increases in size it will
> toss out stray pages which shouldn't be there, then it will start
> reclaiming and swapping out its own pages and eventually it'll get an
> oom-killing.
okay, let me ask a few naive questions about this scheme:
how does this work for a _file_ which is shared between
two guests (e.g. an executable like bash, hardlinked
between guests) when both guests are in a different
zone-based container?
+ assumed that the file is read in the first time,
will it be accounted to the first guest doing so?
+ assumed it is accessed in the second guest, will
it cause any additional cache/mapping besides the
dentry stuff?
+ will container A be able to 'toss out' pages
'shared' with container B (assumed sharing is
possible :)
+ when the container A tosses out the pages for this
executable, will guest B still be able to use them?
+ when the pages are tossed out, will they require
the system to read them in again, or will they
stay available ala swap cache?
> No RSS acounting or page acounting in sight, because we already *have*
> that stuff, at the physical level, in the zone.
I'm fine with that ...
> Overcommitment can be performed by allowing different containers to
> share the same zone set, or by dynamically increasing or decreasing
> the size of a physical container.
here the question is, can a guest have several of
those 'virtual zones' assigned, so that there is a
container specific and a shared zone for example?
> This all works today with fake-numa and cpusets, no kernel changes
> needed.
sounds good!
> It could be made to work fairly simply with a multi-zone approach, or
> with resizeable zones.
>
> I'd be interested in knowing what you think the shortcomings of
> this are likely to be,.
will do so once I have a better understanding how this
approach will work ...
TIA,
Herbert
next prev parent reply other threads:[~2007-03-13 14:59 UTC|newest]
Thread overview: 129+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-06 14:42 [RFC][PATCH 0/7] Resource controllers based on process containers Pavel Emelianov
2007-03-06 14:49 ` [RFC][PATCH 1/7] Resource counters Pavel Emelianov
2007-03-07 4:03 ` Balbir Singh
2007-03-07 7:19 ` Pavel Emelianov
2007-03-09 16:37 ` Herbert Poetzl
2007-03-11 9:01 ` Pavel Emelianov
2007-03-11 19:00 ` Eric W. Biederman
2007-03-12 1:16 ` Herbert Poetzl
2007-03-13 9:09 ` Eric W. Biederman
2007-03-13 9:27 ` Pavel Emelianov
2007-03-13 9:49 ` [Devel] " Kirill Korotaev
2007-03-13 15:21 ` Herbert Poetzl
2007-03-13 15:41 ` Pavel Emelianov
2007-03-13 16:07 ` Srivatsa Vaddagiri
2007-03-14 7:12 ` Pavel Emelianov
2007-03-15 16:51 ` Eric W. Biederman
2007-03-13 16:32 ` Herbert Poetzl
2007-03-06 14:55 ` [RFC][PATCH 2/7] RSS controller core Pavel Emelianov
2007-03-06 22:00 ` Andrew Morton
2007-03-09 16:48 ` Herbert Poetzl
2007-03-11 9:08 ` Pavel Emelianov
2007-03-11 14:32 ` Herbert Poetzl
2007-03-11 15:04 ` Pavel Emelianov
2007-03-12 0:41 ` Herbert Poetzl
2007-03-12 8:31 ` Pavel Emelianov
2007-03-12 9:55 ` Balbir Singh
2007-03-12 23:43 ` Herbert Poetzl
2007-03-13 1:57 ` Balbir Singh
2007-03-13 2:24 ` Srivatsa Vaddagiri
2007-03-13 16:06 ` Herbert Poetzl
2007-03-11 12:26 ` Kirill Korotaev
2007-03-11 12:51 ` Andrew Morton
2007-03-11 15:51 ` Balbir Singh
2007-03-11 19:34 ` Eric W. Biederman
2007-03-12 9:23 ` [Devel] " Kirill Korotaev
2007-03-13 9:26 ` Eric W. Biederman
2007-03-13 15:43 ` Kirill Korotaev
2007-03-12 1:00 ` Herbert Poetzl
2007-03-12 9:02 ` Pavel Emelianov
2007-03-12 21:11 ` Herbert Poetzl
2007-03-13 7:17 ` Pavel Emelianov
2007-03-13 15:05 ` Herbert Poetzl
2007-03-13 15:32 ` Pavel Emelianov
2007-03-13 15:10 ` Kirill Korotaev
2007-03-13 15:11 ` Herbert Poetzl
2007-03-13 15:54 ` Kirill Korotaev
2007-03-12 18:42 ` Dave Hansen
2007-03-12 22:41 ` Herbert Poetzl
2007-03-12 23:02 ` Dave Hansen
2007-03-18 16:58 ` Eric W. Biederman
2007-03-13 6:04 ` Andrew Morton
2007-03-13 10:19 ` [Devel] " Kirill Korotaev
2007-03-13 11:48 ` Andrew Morton
2007-03-13 14:59 ` Herbert Poetzl [this message]
2007-03-13 17:05 ` Dave Hansen
2007-03-14 15:38 ` Mel Gorman
2007-03-14 20:42 ` Dave Hansen
2007-03-20 18:57 ` Mel Gorman
2007-03-18 22:44 ` [Devel] " Paul Menage
2007-03-19 17:41 ` Eric W. Biederman
2007-03-13 17:26 ` Dave Hansen
2007-03-13 19:09 ` Alan Cox
2007-03-13 20:28 ` Dave Hansen
2007-03-16 0:55 ` Eric W. Biederman
2007-03-16 16:31 ` Dave Hansen
2007-03-16 18:54 ` Eric W. Biederman
2007-03-16 19:46 ` Dave Hansen
2007-03-18 17:42 ` Eric W. Biederman
2007-03-19 15:48 ` Herbert Poetzl
2007-03-20 16:15 ` controlling mmap()'d vs read/write() pages Dave Hansen
2007-03-20 21:19 ` Eric W. Biederman
2007-03-23 0:51 ` Herbert Poetzl
2007-03-23 5:57 ` Nick Piggin
2007-03-23 10:12 ` Eric W. Biederman
2007-03-23 10:47 ` Nick Piggin
2007-03-23 12:21 ` Eric W. Biederman
2007-03-28 7:33 ` Nick Piggin
2007-03-23 16:41 ` Dave Hansen
2007-03-23 18:16 ` Herbert Poetzl
2007-03-28 9:18 ` Balbir Singh
2007-03-14 16:47 ` [RFC][PATCH 2/7] RSS controller core Mel Gorman
2007-03-07 5:37 ` Balbir Singh
2007-03-07 7:27 ` Pavel Emelianov
2007-03-06 14:58 ` [RFC][PATCH 3/7] Data structures changes for RSS accounting Pavel Emelianov
2007-03-11 19:13 ` Eric W. Biederman
2007-03-12 16:16 ` Kirill Korotaev
2007-03-12 16:48 ` Dave Hansen
2007-03-12 17:19 ` Pavel Emelianov
2007-03-12 17:27 ` Dave Hansen
2007-03-13 7:10 ` Pavel Emelianov
2007-03-12 17:21 ` Balbir Singh
2007-03-06 15:00 ` [RFC][PATCH 4/7] RSS accounting hooks over the code Pavel Emelianov
2007-03-11 19:14 ` Eric W. Biederman
2007-03-12 16:23 ` Kirill Korotaev
2007-03-12 16:50 ` Dave Hansen
2007-03-12 17:07 ` Kirill Korotaev
2007-03-12 17:33 ` Dave Hansen
2007-03-13 9:43 ` Eric W. Biederman
2007-03-12 23:54 ` Herbert Poetzl
2007-03-13 9:58 ` Eric W. Biederman
2007-03-13 10:25 ` Nick Piggin
2007-03-13 16:01 ` Eric W. Biederman
2007-03-14 3:51 ` Nick Piggin
2007-03-14 6:42 ` Balbir Singh
2007-03-14 6:57 ` Nick Piggin
2007-03-14 7:48 ` Balbir Singh
2007-03-14 13:25 ` Vaidyanathan Srinivasan
2007-03-14 13:49 ` Nick Piggin
2007-03-14 14:43 ` Vaidyanathan Srinivasan
2007-03-14 16:16 ` Kirill Korotaev
2007-03-15 5:01 ` Nick Piggin
2007-03-15 5:44 ` Balbir Singh
2007-03-28 20:15 ` Ethan Solomita
2007-03-14 15:37 ` Cedric Le Goater
2007-03-14 15:45 ` Pavel Emelianov
2007-03-06 15:03 ` [RFC][PATCH 5/7] Per-container OOM killer and page reclamation Pavel Emelianov
2007-03-09 21:21 ` Balbir Singh
2007-03-11 8:41 ` Pavel Emelianov
2007-03-06 15:04 ` [RFC][PATCH 6/7] Account for the number of tasks within container Pavel Emelianov
2007-03-07 2:00 ` Paul Menage
2007-03-07 7:13 ` Pavel Emelianov
2007-03-08 13:49 ` Paul Menage
2007-03-11 8:36 ` Pavel Emelianov
2007-03-06 15:07 ` [RFC][PATCH 7/7] Account for the number of files opened " Pavel Emelianov
2007-03-07 2:02 ` [RFC][PATCH 0/7] Resource controllers based on process containers Paul Menage
2007-03-07 7:30 ` Pavel Emelianov
2007-03-07 6:52 ` Balbir Singh
2007-03-07 7:32 ` Pavel Emelianov
2007-03-07 9:43 ` Kirill Korotaev
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