From: Ingo Molnar <mingo@elte.hu>
To: Christoph Hellwig <hch@infradead.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH] mm: remove global locks from mm/highmem.c
Date: Sun, 28 Jan 2007 16:17:00 +0100 [thread overview]
Message-ID: <20070128151700.GA7644@elte.hu> (raw)
In-Reply-To: <20070128144933.GD16552@infradead.org>
* Christoph Hellwig <hch@infradead.org> wrote:
> On Sun, Jan 28, 2007 at 03:11:34PM +0100, Peter Zijlstra wrote:
> > Eradicate global locks.
> >
> > - kmap_lock is removed by extensive use of atomic_t, a new flush
> > scheme and modifying set_page_address to only allow NULL<->virt
> > transitions.
>
> What's the point for this? [...]
scalability. I did lock profiling on the -rt kernel, which exposes such
things nicely. Half of the lock contention events during kernel compile
were due to kmap(). (The system had 2 GB of RAM, so 40% lowmem, 60%
highmem.)
> [...] In doubt we just need to convert that caller to kmap_atomic.
the pagecache ones cannot be converted to kmap_atomic, because we can
block while holding them. Plus kmap_atomic is quite a bit slower than
this scalable version of kmap().
Ingo
ps. please fix your mailer to not emit Mail-Followup-To headers. In Mutt
you can do this via "set followup_to=no" in your .muttrc.
WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@elte.hu>
To: Christoph Hellwig <hch@infradead.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH] mm: remove global locks from mm/highmem.c
Date: Sun, 28 Jan 2007 16:17:00 +0100 [thread overview]
Message-ID: <20070128151700.GA7644@elte.hu> (raw)
In-Reply-To: <20070128144933.GD16552@infradead.org>
* Christoph Hellwig <hch@infradead.org> wrote:
> On Sun, Jan 28, 2007 at 03:11:34PM +0100, Peter Zijlstra wrote:
> > Eradicate global locks.
> >
> > - kmap_lock is removed by extensive use of atomic_t, a new flush
> > scheme and modifying set_page_address to only allow NULL<->virt
> > transitions.
>
> What's the point for this? [...]
scalability. I did lock profiling on the -rt kernel, which exposes such
things nicely. Half of the lock contention events during kernel compile
were due to kmap(). (The system had 2 GB of RAM, so 40% lowmem, 60%
highmem.)
> [...] In doubt we just need to convert that caller to kmap_atomic.
the pagecache ones cannot be converted to kmap_atomic, because we can
block while holding them. Plus kmap_atomic is quite a bit slower than
this scalable version of kmap().
Ingo
ps. please fix your mailer to not emit Mail-Followup-To headers. In Mutt
you can do this via "set followup_to=no" in your .muttrc.
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next prev parent reply other threads:[~2007-01-28 15:18 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-01-28 14:11 [PATCH] mm: remove global locks from mm/highmem.c Peter Zijlstra
2007-01-28 14:11 ` Peter Zijlstra
2007-01-28 14:49 ` Christoph Hellwig
2007-01-28 14:49 ` Christoph Hellwig
2007-01-28 15:17 ` Ingo Molnar [this message]
2007-01-28 15:17 ` Ingo Molnar
2007-01-28 15:28 ` Christoph Hellwig
2007-01-28 15:28 ` Christoph Hellwig
2007-01-28 15:48 ` Ingo Molnar
2007-01-28 15:48 ` Ingo Molnar
2007-01-28 15:54 ` Christoph Hellwig
2007-01-28 15:54 ` Christoph Hellwig
2007-01-28 18:19 ` Ingo Molnar
2007-01-28 18:19 ` Ingo Molnar
2007-01-28 22:29 ` Andrew Morton
2007-01-28 22:29 ` Andrew Morton
2007-01-29 2:52 ` Nick Piggin
2007-01-29 2:52 ` Nick Piggin
2007-01-29 9:44 ` Peter Zijlstra
2007-01-29 9:44 ` Peter Zijlstra
2007-01-30 1:31 ` Martin J. Bligh
2007-01-30 1:31 ` Martin J. Bligh
2007-01-30 1:41 ` Andrew Morton
2007-01-30 1:41 ` Andrew Morton
2007-01-30 1:49 ` Martin J. Bligh
2007-01-30 1:49 ` Martin J. Bligh
2007-01-30 2:15 ` Andrew Morton
2007-01-30 2:15 ` Andrew Morton
2007-01-31 0:44 ` David Chinner
2007-01-31 0:44 ` David Chinner
2007-01-31 1:11 ` Andrew Morton
2007-01-31 1:11 ` Andrew Morton
2007-01-31 3:22 ` David Chinner
2007-01-31 3:22 ` David Chinner
2007-02-02 12:05 ` Christoph Hellwig
2007-02-02 12:05 ` Christoph Hellwig
2007-02-02 19:24 ` Matt Mackall
2007-02-02 19:24 ` Matt Mackall
2007-02-02 23:16 ` David Chinner
2007-02-02 23:16 ` David Chinner
2007-02-02 23:14 ` David Chinner
2007-02-02 23:14 ` David Chinner
2007-01-29 19:08 ` Ingo Molnar
2007-01-29 19:08 ` Ingo Molnar
2007-01-29 19:19 ` Hugh Dickins
2007-01-29 19:19 ` Hugh Dickins
2007-01-29 19:53 ` Ingo Molnar
2007-01-29 19:53 ` Ingo Molnar
2007-01-29 20:06 ` Ingo Molnar
2007-01-29 20:06 ` Ingo Molnar
2007-01-30 2:02 ` Nick Piggin
2007-01-30 2:02 ` Nick Piggin
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