Messages in this thread | | | Subject | Re: [PATCH] slab: avoid unnecessary touching of a partial slab | From | Zhao Jin <> | Date | Fri, 26 Aug 2011 23:02:34 +0800 |
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On Fri, 2011-08-26 at 09:50 -0500, Christoph Lameter wrote: > On Fri, 26 Aug 2011, Zhao Jin wrote: > > > On Fri, 2011-08-26 at 09:08 -0500, Christoph Lameter wrote: > > > On Fri, 26 Aug 2011, Zhao Jin wrote: > > > > > > > In cache_alloc_refill(), after refilling from a partial slab, if the > > > > slab remains partial, it would be deleted from and then added again to > > > > the partial list. As the slab is the first element in the list before > > > > deletion, such behavior has no effect. This patch avoids touching the > > > > slab in this case. > > > > > > The list_del/list_add action is a list_move. > > > > But in cache_alloc_refill(), it is the first slab (that is: its list > > field is pointed by the l3->slabs_partial.next) that is picked from the > > partial list for refilling. Assume it remains partial after that. Since > > list_add inserts a new element after the head (l3->slabs_partial), the > > position of the slab in the partial list won't change after > > list_del/list_add: it will be still the first element. Therefore, > > list_del/list_add has done nothing actually in this case. > > Correct but still tthe del/add is a list_move operation. Convert that the > other case as well? > Yes. The patch avoids list_del/list_add only if it is the case that a partial slab was used for refilling and remains partial (that is: partial => partial). If it is not the case( so it must be either partial => full, free => full or free => partial) the patched code behaves the same as current (list_del/list_add).
Regards, zhj
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