Re: [PATCH][-mm][0/2] page reclaim throttle take4

[Balbir Singh <balbir@linux.vnet.ibm.com>]

KOSAKI Motohiro wrote:
> changelog
> ========================================
>   v3 -> v4:
>      o fixed recursive shrink_zone problem.
>      o add last_checked variable in shrink_zone for 
>        prevent corner case regression.
> 
>   v2 -> v3:
>      o use wake_up() instead wake_up_all()
>      o max reclaimers can be changed Kconfig option and sysctl.
>      o some cleanups
> 
>   v1 -> v2:
>      o make per zone throttle 
> 
> 
> background
> =====================================
> current VM implementation doesn't has limit of # of parallel reclaim.
> when heavy workload, it bring to 2 bad things
>   - heavy lock contention
>   - unnecessary swap out
> 
> The end of last year, KAMEZA Hiroyuki proposed the patch of page 
> reclaim throttle and explain it improve reclaim time.
> 	http://marc.info/?l=linux-mm&m=119667465917215&w=2
> 
> but unfortunately it works only memcgroup reclaim.
> Today, I implement it again for support global reclaim and mesure it.
> 
> 
> benefit
> =====================================
> <<1. fix the bug of incorrect OOM killer>>
> 
> if do following commanc, sometimes OOM killer happened.
> (OOM happend about 10%)
> 
>  $ ./hackbench 125 process 1000
> 
> because following bad scenario happend.
> 
>    1. memory shortage happend.
>    2. many task call shrink_zone at the same time.
>    3. all page are isolated from LRU at the same time.
>    4. the last task can't isolate any page from LRU.
>    5. it cause reclaim failure.
>    6. it cause OOM killer.
> 
> my patch is directly solution for that problem.
> 
> 
> <<2. performance improvement>>
> I mesure various parameter of hackbench.
> 
> result number mean seconds (i.e. smaller is better)
> 

The results look quite impressive. Have you seen how your patches integrate with
Rik's LRU changes?

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL

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