Messages in this thread | | | Date | Fri, 18 Dec 2009 15:38:11 +0200 | From | Avi Kivity <> | Subject | Re: [PATCH v2] vmscan: limit concurrent reclaimers in shrink_zone |
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On 12/11/2009 11:46 PM, Rik van Riel wrote: > Under very heavy multi-process workloads, like AIM7, the VM can > get into trouble in a variety of ways. The trouble start when > there are hundreds, or even thousands of processes active in the > page reclaim code. > > Not only can the system suffer enormous slowdowns because of > lock contention (and conditional reschedules) between thousands > of processes in the page reclaim code, but each process will try > to free up to SWAP_CLUSTER_MAX pages, even when the system already > has lots of memory free. > > It should be possible to avoid both of those issues at once, by > simply limiting how many processes are active in the page reclaim > code simultaneously. > > If too many processes are active doing page reclaim in one zone, > simply go to sleep in shrink_zone(). > > On wakeup, check whether enough memory has been freed already > before jumping into the page reclaim code ourselves. We want > to use the same threshold here that is used in the page allocator > for deciding whether or not to call the page reclaim code in the > first place, otherwise some unlucky processes could end up freeing > memory for the rest of the system. > > > > Control how to kill processes when uncorrected memory error (typically > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 30fe668..ed614b8 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -345,6 +345,10 @@ struct zone { > /* Zone statistics */ > atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS]; > > + /* Number of processes running page reclaim code on this zone. */ > + atomic_t concurrent_reclaimers; > + wait_queue_head_t reclaim_wait; > + >
Counting semaphore?
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
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