Messages in this thread | | | Date | Mon, 19 Feb 2007 16:46:33 +0530 | From | Balbir Singh <> | Subject | Re: [RFC][PATCH][3/4] Add reclaim support |
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Andrew Morton wrote: > On Mon, 19 Feb 2007 16:20:53 +0530 Balbir Singh <balbir@in.ibm.com> wrote: > >>>> + * so, is the container over it's limit. Returns 1 if the container is above >>>> + * its limit. >>>> + */ >>>> +int memctlr_mm_overlimit(struct mm_struct *mm, void *sc_cont) >>>> +{ >>>> + struct container *cont; >>>> + struct memctlr *mem; >>>> + long usage, limit; >>>> + int ret = 1; >>>> + >>>> + if (!sc_cont) >>>> + goto out; >>>> + >>>> + read_lock(&mm->container_lock); >>>> + cont = mm->container; >>>> + >>>> + /* >>>> + * Regular reclaim, let it proceed as usual >>>> + */ >>>> + if (!sc_cont) >>>> + goto out; >>>> + >>>> + ret = 0; >>>> + if (cont != sc_cont) >>>> + goto out; >>>> + >>>> + mem = memctlr_from_cont(cont); >>>> + usage = atomic_long_read(&mem->counter.usage); >>>> + limit = atomic_long_read(&mem->counter.limit); >>>> + if (limit && (usage > limit)) >>>> + ret = 1; >>>> +out: >>>> + read_unlock(&mm->container_lock); >>>> + return ret; >>>> +} >>> hm, I wonder how much additional lock traffic all this adds. >>> >> It's a read_lock() and most of the locks are read_locks >> which allow for concurrent access, until the container >> changes or goes away > > read_lock isn't free, and I suspect we're calling this function pretty > often (every pagefault?) It'll be measurable on some workloads, on some > hardware. > > It probably won't be terribly bad because each lock-taking is associated > with a clear_page(). But still, if there's any possibility of lightening > the locking up, now is the time to think about it. >
Yes, good point. I'll revisit to see if barriers can replace the locking or if the locking is required at all?
>>>> @@ -66,6 +67,9 @@ struct scan_control { >>>> int swappiness; >>>> >>>> int all_unreclaimable; >>>> + >>>> + void *container; /* Used by containers for reclaiming */ >>>> + /* pages when the limit is exceeded */ >>>> }; >>> eww. Why void*? >>> >> I did not want to expose struct container in mm/vmscan.c. > > It's already there, via rmap.h >
Yes, true
>> An additional >> thought was that no matter what container goes in the field would be >> useful for reclaim. > > Am having trouble parsing that sentence ;) > >
The thought was that irrespective of the infrastructure that goes in having an entry for reclaim in scan_control would be useful. I guess the name exposes what the type tries to hide :-)
-- Warm Regards, Balbir Singh - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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