From: Dave Chinner <david@fromorbit.com>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: Andreas Dilger <adilger@dilger.ca>,
Christoph Hellwig <hch@infradead.org>,
"linux-fsdevel@vger.kernel.org Devel"
<linux-fsdevel@vger.kernel.org>,
xfs@oss.sgi.com
Subject: Re: XFS status update for May 2012
Date: Tue, 19 Jun 2012 11:27:00 +1000 [thread overview]
Message-ID: <20120619012700.GH25389@dastard> (raw)
In-Reply-To: <4FDF9998.6020205@sandeen.net>
On Mon, Jun 18, 2012 at 04:11:52PM -0500, Eric Sandeen wrote:
> On 6/18/12 1:25 PM, Andreas Dilger wrote:
> > On 2012-06-18, at 6:08 AM, Christoph Hellwig wrote:
> >> May saw the release of Linux 3.4, including a decent sized XFS update.
> >> Remarkable XFS features in Linux 3.4 include moving over all metadata
> >> updates to use transactions, the addition of a work queue for the
> >> low-level allocator code to avoid stack overflows due to extreme stack
> >> use in the Linux VM/VFS call chain,
> >
> > This is essentially a workaround for too-small stacks in the kernel,
> > which we've had to do at times as well, by doing work in a separate
> > thread (with a new stack) and waiting for the results? This is a
> > generic problem that any reasonably-complex filesystem will have when
> > running under memory pressure on a complex storage stack (e.g. LVM +
> > iSCSI), but causes unnecessary context switching.
> >
> > Any thoughts on a better way to handle this, or will there continue
> > to be a 4kB stack limit and hack around this with repeated kmalloc
>
> well, 8k on x86_64 (not 4k) right? But still...
>
> Maybe it's still a partial hack but it's more generic - should we have
> IRQ stacks like x86 has? (I think I'm right that that only exists
> on x86 / 32-bit) - is there any downside to that?
We already have irq stacks for x86-64 - the stackunwinder knows
about them so when you get a stack trace from the interrupt stack is
walks back across to the thread stack at the appropriate point...
See dump_trace() in arch/x86/kernel/dumpstack_64.c
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: Andreas Dilger <adilger@dilger.ca>,
Christoph Hellwig <hch@infradead.org>,
"linux-fsdevel@vger.kernel.org Devel"
<linux-fsdevel@vger.kernel.org>,
xfs@oss.sgi.com
Subject: Re: XFS status update for May 2012
Date: Tue, 19 Jun 2012 11:27:00 +1000 [thread overview]
Message-ID: <20120619012700.GH25389@dastard> (raw)
In-Reply-To: <4FDF9998.6020205@sandeen.net>
On Mon, Jun 18, 2012 at 04:11:52PM -0500, Eric Sandeen wrote:
> On 6/18/12 1:25 PM, Andreas Dilger wrote:
> > On 2012-06-18, at 6:08 AM, Christoph Hellwig wrote:
> >> May saw the release of Linux 3.4, including a decent sized XFS update.
> >> Remarkable XFS features in Linux 3.4 include moving over all metadata
> >> updates to use transactions, the addition of a work queue for the
> >> low-level allocator code to avoid stack overflows due to extreme stack
> >> use in the Linux VM/VFS call chain,
> >
> > This is essentially a workaround for too-small stacks in the kernel,
> > which we've had to do at times as well, by doing work in a separate
> > thread (with a new stack) and waiting for the results? This is a
> > generic problem that any reasonably-complex filesystem will have when
> > running under memory pressure on a complex storage stack (e.g. LVM +
> > iSCSI), but causes unnecessary context switching.
> >
> > Any thoughts on a better way to handle this, or will there continue
> > to be a 4kB stack limit and hack around this with repeated kmalloc
>
> well, 8k on x86_64 (not 4k) right? But still...
>
> Maybe it's still a partial hack but it's more generic - should we have
> IRQ stacks like x86 has? (I think I'm right that that only exists
> on x86 / 32-bit) - is there any downside to that?
We already have irq stacks for x86-64 - the stackunwinder knows
about them so when you get a stack trace from the interrupt stack is
walks back across to the thread stack at the appropriate point...
See dump_trace() in arch/x86/kernel/dumpstack_64.c
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2012-06-19 1:28 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-18 12:08 XFS status update for May 2012 Christoph Hellwig
2012-06-18 12:08 ` Christoph Hellwig
2012-06-18 18:25 ` Andreas Dilger
2012-06-18 18:25 ` Andreas Dilger
2012-06-18 18:43 ` Ben Myers
2012-06-18 18:43 ` Ben Myers
2012-06-18 20:36 ` Andreas Dilger
2012-06-18 20:36 ` Andreas Dilger
2012-06-19 1:20 ` Dave Chinner
2012-06-19 1:20 ` Dave Chinner
2012-06-18 21:11 ` Eric Sandeen
2012-06-18 21:11 ` Eric Sandeen
2012-06-18 21:16 ` Eric Sandeen
2012-06-18 21:16 ` Eric Sandeen
2012-06-19 1:27 ` Dave Chinner [this message]
2012-06-19 1:27 ` Dave Chinner
2012-06-19 1:11 ` Dave Chinner
2012-06-19 1:11 ` Dave Chinner
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