Messages in this thread Patch in this message | | | Subject | Re: [PATCH 01/11] mm: page_alloc: set_migratetype_isolate: drain PCP prior to isolating | Date | Sun, 01 Jan 2012 19:52:16 +0100 | From | "Michal Nazarewicz" <> |
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On Sun, 01 Jan 2012 17:06:53 +0100, Gilad Ben-Yossef <gilad@benyossef.com> wrote:
> 2012/1/1 Michal Nazarewicz <mina86@mina86.com>: >> Looks interesting, I'm not entirely sure why it does not end up a race >> condition, but in case of __zone_drain_all_pages() we already hold
> If a page is in the PCP list when we check, you'll send the IPI and all is well. > > If it isn't when we check and gets added later you could just the same have > situation where we send the IPI, try to do try an empty PCP list and then > the page gets added. So we are not adding a race condition that is not there > already :-)
Right, makes sense.
>> zone->lock, so my fears are somehow gone.. I'll give it a try, and prepare >> a patch for __zone_drain_all_pages().
> I plan to send V5 of the IPI noise patch after some testing. It has a new > version of the drain_all_pages, with no allocation in the reclaim path > and no locking. You might want to wait till that one is out to base on it.
This shouldn't be a problem for my case as set_migratetype_isolate() is hardly ever called in reclaim path. :)
The change so far seems rather obvious:
mm/page_alloc.c | 14 +++++++++++++- 1 files changed, 13 insertions(+), 1 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 424d36a..eaa686b 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1181,7 +1181,19 @@ static void __zone_drain_local_pages(void *arg) */ static void __zone_drain_all_pages(struct zone *zone) { - on_each_cpu(__zone_drain_local_pages, zone, 1); + struct per_cpu_pageset *pcp; + cpumask_var_t cpus; + int cpu; + + if (likely(zalloc_cpumask_var(&cpus, GFP_ATOMIC | __GFP_NOWARN))) { + for_each_online_cpu(cpu) + if (per_cpu_ptr(zone->pageset, cpu)->pcp.count) + cpumask_set_cpu(cpu, cpus); + on_each_cpu_mask(cpus, __zone_drain_local_pages, zone, 1); + free_cpumask_var(cpus); + } else { + on_each_cpu(__zone_drain_local_pages, zone, 1); + } }
#ifdef CONFIG_HIBERNATION -- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michał “mina86” Nazarewicz (o o) ooo +----<email/xmpp: mpn@google.com>--------------ooO--(_)--Ooo-- -- 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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