From: David Rientjes <rientjes@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
Fengguang Wu <fengguang.wu@intel.com>,
David Cohen <david.a.cohen@linux.intel.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Damien Ramonda <damien.ramonda@intel.com>,
Jan Kara <jack@suse.cz>, Linus <torvalds@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH V5] mm readahead: Fix readahead fail for no local memory and limit readahead pages
Date: Thu, 6 Feb 2014 15:58:17 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.02.1402061557210.5061@chino.kir.corp.google.com> (raw)
In-Reply-To: <alpine.DEB.2.02.1402061537180.3441@chino.kir.corp.google.com>
On Thu, 6 Feb 2014, David Rientjes wrote:
> > > > > +#define MAX_REMOTE_READAHEAD 4096UL
> Normally it wouldn't matter because there's no significant downside to it
> racing, things like mempolicies which use numa_node_id() extensively would
> result in, oops, a page allocation on the wrong node.
>
> This stands out to me, though, because you're expecting the calculation to
> be correct for a specific node.
>
> The patch is still wrong, though, it should just do
>
> int node = ACCESS_ONCE(numa_mem_id());
> return min(nr, (node_page_state(node, NR_INACTIVE_FILE) +
> node_page_state(node, NR_FREE_PAGES)) / 2);
>
> since we want to readahead based on the cpu's local node, the comment
> saying we're reading ahead onto "remote memory" is wrong since a
> memoryless node has local affinity to numa_mem_id().
>
Oops, forgot about the MAX_REMOTE_READAHEAD which needs to be factored in
as well, but this handles the bound on local node's statistics.
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next prev parent reply other threads:[~2014-02-06 23:58 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-22 10:53 Raghavendra K T
2014-02-03 8:30 ` Raghavendra K T
2014-02-06 22:51 ` Andrew Morton
2014-02-06 22:58 ` David Rientjes
2014-02-06 23:22 ` Andrew Morton
2014-02-06 23:48 ` David Rientjes
2014-02-06 23:58 ` David Rientjes [this message]
2014-02-07 10:42 ` Raghavendra K T
2014-02-07 20:41 ` David Rientjes
2014-02-10 8:21 ` Raghavendra K T
2014-02-10 10:05 ` David Rientjes
2014-02-10 12:25 ` Raghavendra K T
2014-02-10 21:35 ` David Rientjes
2014-02-13 7:07 ` Raghavendra K T
2014-02-13 8:05 ` David Rientjes
2014-02-13 10:04 ` Raghavendra K T
2014-02-13 22:41 ` David Rientjes
2014-02-14 0:14 ` Nishanth Aravamudan
2014-02-14 0:37 ` Linus Torvalds
2014-02-14 0:45 ` Andrew Morton
2014-02-14 4:32 ` Nishanth Aravamudan
2014-02-14 10:54 ` David Rientjes
2014-02-17 19:28 ` Nishanth Aravamudan
2014-02-17 23:14 ` David Rientjes
2014-02-18 1:31 ` Nishanth Aravamudan
2014-02-17 22:59 ` Linus Torvalds
2014-02-14 7:43 ` Jan Kara
2014-02-17 22:57 ` Linus Torvalds
2014-02-14 5:47 ` Nishanth Aravamudan
2014-02-13 21:06 ` Andrew Morton
2014-02-13 21:42 ` Nishanth Aravamudan
2014-02-10 8:29 ` [RFC PATCH V5 RESEND] " Raghavendra K T
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