Re: [patch] slub: fix a code merge error

On Fri, 2011-11-11 at 04:30 +0800, Pekka Enberg wrote:

On Thu, Nov 10, 2011 at 10:18 PM, David Rientjes [off-list ref] wrote:

quoted

On Thu, 10 Nov 2011, Shaohua Li wrote:

quoted

Looks there is a merge error in the slub tree. DEACTIVATE_TO_TAIL != 1.
And this will cause performance regression.

Signed-off-by: Shaohua Li <redacted>

diff --git a/mm/slub.c b/mm/slub.c
index 7d2a996..60e16c4 100644
--- a/mm/slub.c
+++ b/mm/slub.c

@@ -1904,7 +1904,8 @@ static void unfreeze_partials(struct kmem_cache *s)
                              if (l == M_PARTIAL)
                                      remove_partial(n, page);
                              else
-                                     add_partial(n, page, 1);
+                                     add_partial(n, page,
+                                             DEACTIVATE_TO_TAIL);

                              l = m;
                      }

Acked-by: David Rientjes <rientjes@google.com>

Not sure where the "merge error" is, though, this is how it was proposed
on linux-mm each time the patch was posted.  Probably needs a better title
and changelog.

Indeed. Please resend with proper subject and changelog with
Christoph's and David's ACKs included.

Subject: slub: use correct parameter to add a page to partial list tail

unfreeze_partials() needs add the page to partial list tail, since such page
hasn't too many free objects. We now explictly use DEACTIVATE_TO_TAIL for this,
while DEACTIVATE_TO_TAIL != 1. This will cause performance regression (eg, more
lock contention in node->list_lock) without below fix.

Signed-off-by: Shaohua Li <redacted>
Acked-by: Christoph Lameter <redacted>
Acked-by: David Rientjes <rientjes@google.com>

diff --git a/mm/slub.c b/mm/slub.c
index 7d2a996..60e16c4 100644
--- a/mm/slub.c
+++ b/mm/slub.c

@@ -1904,7 +1904,8 @@ static void unfreeze_partials(struct kmem_cache *s)
 				if (l == M_PARTIAL)
 					remove_partial(n, page);
 				else
-					add_partial(n, page, 1);
+					add_partial(n, page,
+						DEACTIVATE_TO_TAIL);
 
 				l = m;
 			}


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