Re: [PATCHv2 0/4] Improve performance for SLAB_POISON

2016-02-16 3:44 GMT+09:00 Laura Abbott [off-list ref]:

Hi,

This is a follow up to my previous series
(http://lkml.kernel.org/g/[ref])
This series takes the suggestion of Christoph Lameter and only focuses on
optimizing the slow path where the debug processing runs. The two main
optimizations in this series are letting the consistency checks be skipped and
relaxing the cmpxchg restrictions when we are not doing consistency checks.
With hackbench -g 20 -l 1000 averaged over 100 runs:

Before slub_debug=P
mean 15.607
variance .086
stdev .294

After slub_debug=P
mean 10.836
variance .155
stdev .394

This still isn't as fast as what is in grsecurity unfortunately so there's still
work to be done. Profiling ___slab_alloc shows that 25-50% of time is spent in
deactivate_slab. I haven't looked too closely to see if this is something that
can be optimized.

There is something to be optimized. deactivate_slab() deactivate objects of
freelist one by one and it's useless. And, it deactivates freelist
with two phases.
Deactivating objects except last one and then deactivating last object with
node lock. It would be also optimized although I didn't think deeply.

Thanks.

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