Hi Minchan,

Sorry for late reply.

On 4/25/12 9:42 PM, Minchan Kim wrote:

On 04/25/2012 09:53 PM, Nitin Gupta wrote:

quoted

On 04/25/2012 02:23 AM, Minchan Kim wrote:

quoted

It isn't necessary to align pool size with PAGE_SIZE.
If I missed something, please let me know it.

Signed-off-by: Minchan Kim<minchan@kernel.org>
---
  drivers/staging/zsmalloc/zsmalloc-main.c |    5 ++---
  1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
index 504b6c2..b99ad9e 100644
--- a/drivers/staging/zsmalloc/zsmalloc-main.c
+++ b/drivers/staging/zsmalloc/zsmalloc-main.c

@@ -489,14 +489,13 @@ fail:

  struct zs_pool *zs_create_pool(const char *name, gfp_t flags)
  {
-	int i, error, ovhd_size;
+	int i, error;
  	struct zs_pool *pool;

  	if (!name)
  		return NULL;

-	ovhd_size = roundup(sizeof(*pool), PAGE_SIZE);
-	pool = kzalloc(ovhd_size, GFP_KERNEL);
+	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
  	if (!pool)
  		return NULL;

pool metadata is rounded-up to avoid potential false-sharing problem
(though we could just roundup to cache_line_size()).

Do you really have any hurt by false-sharing problem?
If so, we can change it with

I've never been hit by this false-sharing in any testing but this is 
really just a random chance. Apart from aligning to cache-line size, 
there is no way to ensure some unfortunate read-mostly object never 
falls in the same line.

kzalloc(ALIGN(sizeof(*pool), cache_line_size()), GFP_KERNEL);

Yes, looks better than aligning to PAGE_SIZE.


Thanks,
Nitin

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