From: Gleb Natapov <gleb-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: "Roland Dreier" <rdreier-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>,
"Håkon Bugge" <Haakon.Bugge-UdXhSnd/wVw@public.gmane.org>,
"Jason Gunthorpe"
<jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>,
"Andrew Morton"
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
"Eric B Munson"
<ebmunson-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
rolandd-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org,
pavel-+ZI9xUNit7I@public.gmane.org,
mingo-X9Un+BFzKDI@public.gmane.org,
jsquyres-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org
Subject: Re: [PATCH] ummunotify: Userspace support for MMU notifications
Date: Wed, 14 Apr 2010 11:52:28 +0300 [thread overview]
Message-ID: <20100414085228.GL23554@redhat.com> (raw)
In-Reply-To: <1271181774.4807.1868.camel@twins>
On Tue, Apr 13, 2010 at 08:02:54PM +0200, Peter Zijlstra wrote:
> On Tue, 2010-04-13 at 10:57 -0700, Roland Dreier wrote:
> > Are those system calls the only possible way that virtual to physical
> > mappings can change? Can't page migration or something like that
> > potentially affect things? And even if you did have hooks into every
> > system call that mattered (keep in mind that relying on glibc is not
> > enough, since an MPI application may not use glibc) would decoding them
> > and figuring out what happened really be preferable to a single event
> > type that tells you exactly what address range was affected?
>
> Yeah, virtual<->physical maps can change through swapping, page
> migration, memory compaction, huge-page aggregation (the latter two not
> yet being upstream).
>
> Even mlock() doesn't pin virtual<->physical maps.
Pages registered for RDMA are GUPed so no method above should touch
them. Fork+cow or unmap/map on the other hand can change
virtual<->physical maps. GUPed pages are still GUPed, but they are no
longer mapped into process' virtual address space. MPI copes with
Fork+cow by marking registered memory as MADV_DONTFORK.
--
Gleb.
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WARNING: multiple messages have this Message-ID (diff)
From: Gleb Natapov <gleb@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Roland Dreier" <rdreier@cisco.com>,
"Håkon Bugge" <Haakon.Bugge@Sun.COM>,
"Jason Gunthorpe" <jgunthorpe@obsidianresearch.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Eric B Munson" <ebmunson@us.ibm.com>,
linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
rolandd@cisco.com, pavel@ucw.cz, mingo@elte.hu,
jsquyres@cisco.com
Subject: Re: [PATCH] ummunotify: Userspace support for MMU notifications
Date: Wed, 14 Apr 2010 11:52:28 +0300 [thread overview]
Message-ID: <20100414085228.GL23554@redhat.com> (raw)
In-Reply-To: <1271181774.4807.1868.camel@twins>
On Tue, Apr 13, 2010 at 08:02:54PM +0200, Peter Zijlstra wrote:
> On Tue, 2010-04-13 at 10:57 -0700, Roland Dreier wrote:
> > Are those system calls the only possible way that virtual to physical
> > mappings can change? Can't page migration or something like that
> > potentially affect things? And even if you did have hooks into every
> > system call that mattered (keep in mind that relying on glibc is not
> > enough, since an MPI application may not use glibc) would decoding them
> > and figuring out what happened really be preferable to a single event
> > type that tells you exactly what address range was affected?
>
> Yeah, virtual<->physical maps can change through swapping, page
> migration, memory compaction, huge-page aggregation (the latter two not
> yet being upstream).
>
> Even mlock() doesn't pin virtual<->physical maps.
Pages registered for RDMA are GUPed so no method above should touch
them. Fork+cow or unmap/map on the other hand can change
virtual<->physical maps. GUPed pages are still GUPed, but they are no
longer mapped into process' virtual address space. MPI copes with
Fork+cow by marking registered memory as MADV_DONTFORK.
--
Gleb.
next prev parent reply other threads:[~2010-04-14 8:52 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-12 6:22 [PATCH] ummunotify: Userspace support for MMU notifications Eric B Munson
2010-04-12 6:22 ` Eric B Munson
[not found] ` <1271053337-7121-1-git-send-email-ebmunson-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2010-04-12 20:20 ` Pavel Machek
2010-04-12 20:20 ` Pavel Machek
2010-04-14 16:43 ` [PATCH] ummunotify: fix umn-test build Randy Dunlap
2010-04-14 16:43 ` Randy Dunlap
[not found] ` <20100414094341.ba69842d.randy.dunlap-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
2010-04-17 17:44 ` Eric B Munson
2010-04-17 17:44 ` Eric B Munson
[not found] ` <20100417174404.GB3579-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
2010-04-18 14:38 ` Roland Dreier
2010-04-18 14:38 ` Roland Dreier
2010-04-12 23:03 ` [PATCH] ummunotify: Userspace support for MMU notifications Andrew Morton
[not found] ` <20100412160359.1d9074dc.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2010-04-12 23:59 ` Jason Gunthorpe
2010-04-12 23:59 ` Jason Gunthorpe
[not found] ` <20100412235937.GF15629-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-04-13 8:29 ` Håkon Bugge
2010-04-13 8:29 ` Håkon Bugge
[not found] ` <3251DDDA-D705-4B1E-9595-9C24709EF146-U0mLk4xYmo8@public.gmane.org>
2010-04-13 17:57 ` Roland Dreier
2010-04-13 17:57 ` Roland Dreier
[not found] ` <adahbnfme0j.fsf-BjVyx320WGW9gfZ95n9DRSW4+XlvGpQz@public.gmane.org>
2010-04-13 18:02 ` Peter Zijlstra
2010-04-13 18:02 ` Peter Zijlstra
2010-04-14 5:18 ` Håkon Bugge
2010-04-14 5:18 ` Håkon Bugge
2010-04-14 8:52 ` Gleb Natapov [this message]
2010-04-14 8:52 ` Gleb Natapov
2010-04-15 13:48 ` Peter Zijlstra
2010-04-14 9:06 ` Gleb Natapov
2010-04-14 9:06 ` Gleb Natapov
[not found] ` <20100414090623.GM23554-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2010-04-14 14:36 ` Jeff Squyres
2010-04-14 14:36 ` Jeff Squyres
2010-04-17 17:41 ` Eric B Munson
2010-04-17 17:41 ` Eric B Munson
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