Messages in this thread | | | Date | Tue, 05 Aug 2008 16:16:54 +0530 | From | Balbir Singh <> | Subject | Re: Race condition between putback_lru_page and mem_cgroup_move_list |
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KOSAKI Motohiro wrote: > Hi Balbir-san, > >>> I also think zone's lru lock is unnecessary. >>> So, I guess below "it" indicate lock_page_cgroup, not zone lru lock. >> We need zone LRU lock, since the reclaim paths hold them. Not sure if I >> understand why you call zone's LRU lock unnecessary, could you elaborate please? > > I tought.. > > 1. in general, one data structure should be protected by one lock.
In general yes, but in practice no. We have different paths through which a page can be reclaimed. Consider the following
1. What happens if a global reclaim is in progress at the same time as memory cgroup reclaim and they are both looking at the same page? 2. In the shared reclaim infrastructure, we move pages and update statistics for pages belonging to a particular zone in a particular cgroup.
>> It's on my TODO list. I hope to get to it soon. > > Very good news!
I hope they show the benefit that I expect them too :)
-- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL
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