From: Andrea Arcangeli <aarcange@redhat.com>
To: Hugh Dickins <hugh@veritas.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
Rik van Riel <riel@redhat.com>, Izik Eidus <ieidus@redhat.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
chrisw@redhat.com, device@lanana.org, linux-mm@kvack.org,
nickpiggin@yahoo.com.au
Subject: Re: [PATCH 2/6] ksm: dont allow overlap memory addresses registrations.
Date: Wed, 6 May 2009 16:56:42 +0200 [thread overview]
Message-ID: <20090506145641.GA16078@random.random> (raw)
In-Reply-To: <Pine.LNX.4.64.0905061532240.25289@blonde.anvils>
On Wed, May 06, 2009 at 03:46:31PM +0100, Hugh Dickins wrote:
> As I understand it, KSM won't affect the vm_overcommit behaviour at all.
In short vm_overcommit is a virtual thing, KSM only makes virtual
takes less physical than before. One issue in KSM that was mentioned
was the cgroup accounting if you merge two pages in different groups
but that is kind of a corner case and it'll be handled "somehow" :)
> The only difference would be in how much memory (mostly lowmem)
> KSM's own data structures will take up - as usual, the kernel
> data structures aren't being accounted, but do take up memory.
Oh yeah, on 32bit systems that would be a problem... That lowmem is
taken for eacy virtual address scanned. One more reason to still allow
ksm to all users only selectively through chown/chmod with ioctl or
sysfs permissions with syscall/madvise. Luckily most systems where ksm
is used are 64bit. We don't plan to kmap_atomic around the
rmap_item/tree_item. No ram is allocated in the holes though, so if
there's not a real anonymous page allocated the rmap_item will not be
allocated either (without requiring pending update ;).
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next prev parent reply other threads:[~2009-05-06 14:55 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-04 22:25 [PATCH 0/6] ksm changes (v2) Izik Eidus
2009-05-04 22:25 ` [PATCH 1/6] ksm: limiting the num of mem regions user can register per fd Izik Eidus
2009-05-04 22:25 ` [PATCH 2/6] ksm: dont allow overlap memory addresses registrations Izik Eidus
2009-05-04 22:25 ` [PATCH 3/6] ksm: change the KSM_REMOVE_MEMORY_REGION ioctl Izik Eidus
2009-05-04 22:25 ` [PATCH 4/6] ksm: change the prot handling to use the generic helper functions Izik Eidus
2009-05-04 22:25 ` [PATCH 5/6] ksm: build system make it compile for all archs Izik Eidus
2009-05-04 22:25 ` [PATCH 6/6] ksm: use another miscdevice minor number Izik Eidus
2009-05-06 0:55 ` Rik van Riel
2009-05-06 0:54 ` [PATCH 5/6] ksm: build system make it compile for all archs Rik van Riel
2009-05-06 0:54 ` [PATCH 4/6] ksm: change the prot handling to use the generic helper functions Rik van Riel
2009-05-06 0:53 ` [PATCH 3/6] ksm: change the KSM_REMOVE_MEMORY_REGION ioctl Rik van Riel
2009-05-06 8:38 ` Izik Eidus
2009-05-06 11:16 ` Hugh Dickins
2009-05-06 13:34 ` Andrea Arcangeli
2009-05-06 13:56 ` Izik Eidus
2009-05-06 16:41 ` Hugh Dickins
2009-05-06 16:49 ` Chris Wright
2009-05-06 16:57 ` Hugh Dickins
2009-05-06 17:47 ` Andrea Arcangeli
2009-05-06 16:59 ` Izik Eidus
2009-05-07 11:31 ` Andrea Arcangeli
2009-05-07 13:13 ` Hugh Dickins
2009-05-07 13:23 ` Andrea Arcangeli
2009-05-06 14:25 ` Hugh Dickins
2009-05-06 14:45 ` Andrea Arcangeli
2009-05-06 15:36 ` Chris Wright
2009-05-06 15:27 ` Izik Eidus
2009-05-06 16:14 ` Chris Wright
2009-05-06 16:36 ` Hugh Dickins
2009-05-06 17:09 ` Chris Wright
2009-05-06 17:54 ` Hugh Dickins
2009-05-06 16:26 ` Hugh Dickins
2009-05-06 16:58 ` Izik Eidus
2009-05-06 23:59 ` Chris Wright
2009-05-07 2:41 ` Rik van Riel
2009-05-06 0:43 ` [PATCH 2/6] ksm: dont allow overlap memory addresses registrations Rik van Riel
2009-05-06 9:46 ` Izik Eidus
2009-05-06 12:26 ` Rik van Riel
2009-05-06 12:39 ` Izik Eidus
2009-05-06 13:17 ` Andrea Arcangeli
2009-05-06 13:28 ` Hugh Dickins
2009-05-06 14:02 ` Izik Eidus
2009-05-06 17:11 ` Hugh Dickins
2009-05-06 14:09 ` Andrea Arcangeli
2009-05-06 14:21 ` Alan Cox
2009-05-06 14:46 ` Hugh Dickins
2009-05-06 14:56 ` Andrea Arcangeli [this message]
2009-05-06 23:55 ` Minchan Kim
2009-05-07 0:19 ` Chris Wright
2009-05-07 10:46 ` Andrea Arcangeli
2009-05-07 12:01 ` Minchan Kim
2009-05-06 14:57 ` Izik Eidus
2009-05-06 0:40 ` [PATCH 1/6] ksm: limiting the num of mem regions user can register per fd Rik van Riel
-- strict thread matches above, loose matches on Subject: below --
2009-05-02 22:16 [PATCH 0/6] ksm changes Izik Eidus
2009-05-02 22:16 ` [PATCH 1/6] ksm: limiting the num of mem regions user can register per fd Izik Eidus
2009-05-02 22:16 ` [PATCH 2/6] ksm: dont allow overlap memory addresses registrations Izik Eidus
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