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

On Wed, May 18, 2011 at 01:25:47PM -0700, Andrew Morton wrote:

On Fri, 13 May 2011 16:46:21 -0700
Andi Kleen [off-list ref] wrote:

quoted

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.

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?

I'll look into checkpatch.

-Andi

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