Messages in this thread | | | Date | Thu, 27 Jan 2011 15:14:51 +0100 | From | Johannes Weiner <> | Subject | Re: [patch 2/3] memcg: prevent endless loop on huge page charge |
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Hi Gleb,
On Thu, Jan 27, 2011 at 04:00:24PM +0200, Gleb Natapov wrote: > On Thu, Jan 27, 2011 at 02:46:45PM +0100, Johannes Weiner wrote: > > The charging code can encounter a charge size that is bigger than a > > regular page in two situations: one is a batched charge to fill the > > per-cpu stocks, the other is a huge page charge. > > > > This code is distributed over two functions, however, and only the > > outer one is aware of huge pages. In case the charging fails, the > > inner function will tell the outer function to retry if the charge > > size is bigger than regular pages--assuming batched charging is the > > only case. And the outer function will retry forever charging a huge > > page. > > > > This patch makes sure the inner function can distinguish between batch > > charging and a single huge page charge. It will only signal another > > attempt if batch charging failed, and go into regular reclaim when it > > is called on behalf of a huge page. > > > Yeah, that is exactly the case I am debugging right now. Came up with > different solution: pass page_size to __mem_cgroup_do_charge() and > compare csize with page_size (not CHARGE_SIZE). Not sure which solution > it more correct.
I guess it makes no difference, but using CHARGE_SIZE gets away without adding another parameter to __mem_cgroup_do_charge().
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