| |
|
 |
|
 |
|
|
|
| |
|
|
xen-devel
[Xen-devel] Re: Interaction between Xen and XFS: stray RW mappings
|
To: |
David Chinner <dgc@xxxxxxx> |
|
Subject: |
[Xen-devel] Re: Interaction between Xen and XFS: stray RW mappings |
|
From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
|
Date: |
Sun, 14 Oct 2007 16:12:20 -0700 |
|
Cc: |
nickpiggin@xxxxxxxxxxxx, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Morten , Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Bøgeskov <xen-users@xxxxxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, xfs-masters@xxxxxxxxxxx, Mark Williamson <mark.williamson@xxxxxxxxxxxx> |
|
Delivery-date: |
Sun, 14 Oct 2007 16:12:59 -0700 |
|
Envelope-to: |
www-data@xxxxxxxxxxxxxxxxxx |
|
In-reply-to: |
<20071014225618.GN23367404@xxxxxxx> |
|
List-help: |
<mailto:xen-devel-request@lists.xensource.com?subject=help> |
|
List-id: |
Xen developer discussion <xen-devel.lists.xensource.com> |
|
List-post: |
<mailto:xen-devel@lists.xensource.com> |
|
List-subscribe: |
<http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe> |
|
List-unsubscribe: |
<http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe> |
|
References: |
<470FA7C3.90404@xxxxxxxx> <20071014225618.GN23367404@xxxxxxx> |
|
Sender: |
xen-devel-bounces@xxxxxxxxxxxxxxxxxxx |
|
User-agent: |
Thunderbird 2.0.0.5 (X11/20070727) |
David Chinner wrote:
> You mean xfs_buf.c.
>
Yes, sorry.
> And yes, we delay unmapping pages until we have a batch of them
> to unmap. vmap and vunmap do not scale, so this is batching helps
> alleviate some of the worst of the problems.
>
How much performance does it cost? What kind of workloads would it show
up under?
> Realistically, if this delayed release of vmaps is a problem for
> Xen, then I think that some generic VM solution is needed to this
> problem as vmap() is likely to become more common in future (think
> large blocks in filesystems). Nick - any comments?
>
Well, the only real problem is that the pages are returned to the free
pool and reallocated while still being part of a mapping. If the pages
are still owned by the filesystem/pagecache, then there's no problem.
What's the lifetime of things being vmapped/unmapped in xfs? Are they
necessarily being freed when they're unmapped, or could unmapping of
freed memory be more immediate than other memory?
Maybe it just needs a notifier chain or something.
J
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
|
|
|
| |
|
Home