From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Mel Gorman <mgorman@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>,
Nadav Amit <nadav.amit@gmail.com>,
linux-mm@kvack.org,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Subject: Re: Potential race in TLB flush batching?
Date: Fri, 14 Jul 2017 19:02:57 +1000 [thread overview]
Message-ID: <1500022977.2865.88.camel@kernel.crashing.org> (raw)
In-Reply-To: <20170714083114.zhaz3pszrklnrn52@suse.de>
On Fri, 2017-07-14 at 09:31 +0100, Mel Gorman wrote:
> It may also be only a gain on a limited number of architectures depending
> on exactly how an architecture handles flushing. At the time, batching
> this for x86 in the worse-case scenario where all pages being reclaimed
> were mapped from multiple threads knocked 24.4% off elapsed run time and
> 29% off system CPU but only on multi-socket NUMA machines. On UMA, it was
> barely noticable. For some workloads where only a few pages are mapped or
> the mapped pages on the LRU are relatively sparese, it'll make no difference.
>
> The worst-case situation is extremely IPI intensive on x86 where many
> IPIs were being sent for each unmap. It's only worth even considering if
> you see that the time spent sending IPIs for flushes is a large portion
> of reclaim.
Ok, it would be interesting to see how that compares to powerpc with
its HW tlb invalidation broadcasts. We tend to hate them and prefer
IPIs in most cases but maybe not *this* case .. (mostly we find that
IPI + local inval is better for large scale invals, such as full mm on
exit/fork etc...).
In the meantime I found the original commits, we'll dig and see if it's
useful for us.
Cheers,
Ben.
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next prev parent reply other threads:[~2017-07-14 9:03 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-11 0:52 Potential race in TLB flush batching? Nadav Amit
2017-07-11 6:41 ` Mel Gorman
2017-07-11 7:30 ` Nadav Amit
2017-07-11 9:29 ` Mel Gorman
2017-07-11 10:40 ` Nadav Amit
2017-07-11 13:20 ` Mel Gorman
2017-07-11 14:58 ` Andy Lutomirski
2017-07-11 15:53 ` Mel Gorman
2017-07-11 17:23 ` Andy Lutomirski
2017-07-11 19:18 ` Mel Gorman
2017-07-11 20:06 ` Nadav Amit
2017-07-11 21:09 ` Mel Gorman
2017-07-11 20:09 ` Mel Gorman
2017-07-11 21:52 ` Mel Gorman
2017-07-11 22:27 ` Nadav Amit
2017-07-11 22:34 ` Nadav Amit
2017-07-12 8:27 ` Mel Gorman
2017-07-12 23:27 ` Nadav Amit
2017-07-12 23:36 ` Andy Lutomirski
2017-07-12 23:42 ` Nadav Amit
2017-07-13 5:38 ` Andy Lutomirski
2017-07-13 16:05 ` Nadav Amit
2017-07-13 16:06 ` Andy Lutomirski
2017-07-13 6:07 ` Mel Gorman
2017-07-13 16:08 ` Andy Lutomirski
2017-07-13 17:07 ` Mel Gorman
2017-07-13 17:15 ` Andy Lutomirski
2017-07-13 18:23 ` Mel Gorman
2017-07-14 23:16 ` Nadav Amit
2017-07-15 15:55 ` Mel Gorman
2017-07-15 16:41 ` Andy Lutomirski
2017-07-17 7:49 ` Mel Gorman
2017-07-18 21:28 ` Nadav Amit
2017-07-19 7:41 ` Mel Gorman
2017-07-19 19:41 ` Nadav Amit
2017-07-19 19:58 ` Mel Gorman
2017-07-19 20:20 ` Nadav Amit
2017-07-19 21:47 ` Mel Gorman
2017-07-19 22:19 ` Nadav Amit
2017-07-19 22:59 ` Mel Gorman
2017-07-19 23:39 ` Nadav Amit
2017-07-20 7:43 ` Mel Gorman
2017-07-22 1:19 ` Nadav Amit
2017-07-24 9:58 ` Mel Gorman
2017-07-24 19:46 ` Nadav Amit
2017-07-25 7:37 ` Minchan Kim
2017-07-25 8:51 ` Mel Gorman
2017-07-25 9:11 ` Minchan Kim
2017-07-25 10:10 ` Mel Gorman
2017-07-26 5:43 ` Minchan Kim
2017-07-26 9:22 ` Mel Gorman
2017-07-26 19:18 ` Nadav Amit
2017-07-26 23:40 ` Minchan Kim
2017-07-27 0:09 ` Nadav Amit
2017-07-27 0:34 ` Minchan Kim
2017-07-27 0:48 ` Nadav Amit
2017-07-27 1:13 ` Nadav Amit
2017-07-27 7:04 ` Minchan Kim
2017-07-27 7:21 ` Mel Gorman
2017-07-27 16:04 ` Nadav Amit
2017-07-27 17:36 ` Mel Gorman
2017-07-26 23:44 ` Minchan Kim
2017-07-11 22:07 ` Andy Lutomirski
2017-07-11 22:33 ` Mel Gorman
2017-07-14 7:00 ` Benjamin Herrenschmidt
2017-07-14 8:31 ` Mel Gorman
2017-07-14 9:02 ` Benjamin Herrenschmidt [this message]
2017-07-14 9:27 ` Mel Gorman
2017-07-14 22:21 ` Andy Lutomirski
2017-07-11 16:22 ` Nadav Amit
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