Re: [PATCH 16/16] mm/slab: introduce new slab management type, OBJFREELIST_SLAB

2016-01-15 0:32 GMT+09:00 Christoph Lameter [off-list ref]:

On Thu, 14 Jan 2016, Joonsoo Kim wrote:

quoted

SLAB needs a array to manage freed objects in a slab. It is only used
if some objects are freed so we can use free object itself as this array.
This requires additional branch in somewhat critical lock path to check
if it is first freed object or not but that's all we need. Benefits is
that we can save extra memory usage and reduce some computational
overhead by allocating a management array when new slab is created.

Hmmm... But then you need to have an offset in the page struct to
figure out where the freelist starts. One additional level of indirection.
Seems to have some negative impact on performance.

SLAB already keeps the pointer where the freelist starts in the page struct.
So, there is no *additional* negative impact on performance.

quoted

In my system, without enabling CONFIG_DEBUG_SLAB, Almost caches become
OBJFREELIST_SLAB and NORMAL_SLAB (using leftover) which doesn't waste
memory. Following is the result of number of caches with specific slab
management type.

Sounds good.

Thanks.

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