Re: [PATCH 1/4] VM/RMAP: Add infrastructure for batching the rmap chain locking v2

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 18 May 2011 23:14:43 +0200
Andi Kleen <andi@firstfloor.org> wrote:

> On Wed, May 18, 2011 at 01:25:47PM -0700, Andrew Morton wrote:
> > On Fri, 13 May 2011 16:46:21 -0700
> > Andi Kleen <andi@firstfloor.org> wrote:
> > 
> > > In fork and exit it's quite common to take same rmap chain locks
> > > again and again when the whole address space is processed  for a
> > > address space that has a lot of sharing. Also since the locking
> > > has changed to always lock the root anon_vma this can be very
> > > contended.
> > > 
> > > This patch adds a simple wrapper to batch these lock acquisitions
> > > and only reaquire the lock when another is needed. The main
> > > advantage is that when multiple processes are doing this in
> > > parallel they will avoid a lot of communication overhead
> > > on the lock cache line.
> > > 
> > > v2: Address review feedback. Drop lockbreak. Rename init function.
> > 
> > Doesn't compile:
> > 
> > include/linux/rmap.h: In function 'anon_vma_unlock_batch':
> > include/linux/rmap.h:146: error: 'struct anon_vma' has no member named 'lock'
> > mm/rmap.c: In function '__anon_vma_lock_batch':
> > mm/rmap.c:1737: error: 'struct anon_vma' has no member named 'lock'
> > mm/rmap.c:1739: error: 'struct anon_vma' has no member named 'lock'
> > 
> > I think I reported this against the v1 patches.
> 
> Hmm is that against -mm? Which tree exactly?
> 
> Both in Linus' latest and in -next I have
> 
> include/linux/rmap.h:
> 
> struct anon_vma {
>         struct anon_vma *root;  /* Root of this anon_vma tree */
>         spinlock_t lock;        /* Serialize access to vma list */
> 
> So it should compile. And it compiles here of course.

ah, whoop, sorry.  It's getting turned into a mutex, by
mm-convert-anon_vma-lock-to-a-mutex.patch

> To be honest I forgot where the -mm tree is, so I can't check. 
> It's not in its old place on kernel.org anymore?

http://userweb.kernel.org/~akpm/mmotm/

If you dive into the `series' file you'll see that this patch is part of this
series:

mm-mmu_gather-rework.patch
mm-mmu_gather-rework-fix.patch
powerpc-mmu_gather-rework.patch
sparc-mmu_gather-rework.patch
s390-mmu_gather-rework.patch
arm-mmu_gather-rework.patch
sh-mmu_gather-rework.patch
ia64-mmu_gather-rework.patch
um-mmu_gather-rework.patch
mm-now-that-all-old-mmu_gather-code-is-gone-remove-the-storage.patch
mm-powerpc-move-the-rcu-page-table-freeing-into-generic-code.patch
mm-extended-batches-for-generic-mmu_gather.patch
mm-extended-batches-for-generic-mmu_gather-fix.patch
lockdep-mutex-provide-mutex_lock_nest_lock.patch
mm-remove-i_mmap_lock-lockbreak.patch
mm-convert-i_mmap_lock-to-a-mutex.patch
mm-revert-page_lock_anon_vma-lock-annotation.patch
mm-improve-page_lock_anon_vma-comment.patch
mm-use-refcounts-for-page_lock_anon_vma.patch
mm-convert-anon_vma-lock-to-a-mutex.patch
mm-optimize-page_lock_anon_vma-fast-path.patch
mm-uninline-large-generic-tlbh-functions.patch

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