From: Wei Yang <richard.weiyang@gmail.com>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Wei Yang <richard.weiyang@gmail.com>,
willy@infradead.org, mhocko@suse.com, linux-mm@kvack.org,
akpm@linux-foundation.org
Subject: Re: [RFC] put page to pcp->lists[] tail if it is not on the same node
Date: Sat, 20 Oct 2018 16:33:18 +0000 [thread overview]
Message-ID: <20181020163318.72oqszgdtqfafycu@master> (raw)
In-Reply-To: <20181019083818.GQ5819@techsingularity.net>
On Fri, Oct 19, 2018 at 09:38:18AM +0100, Mel Gorman wrote:
>On Fri, Oct 19, 2018 at 04:33:03AM +0000, Wei Yang wrote:
>> node
>> Reply-To: Wei Yang <richard.weiyang@gmail.com>
>>
>> Masters,
>>
>> During the code reading, I pop up this idea.
>>
>> In case we put some intelegence of NUMA node to pcp->lists[], we may
>> get a better performance.
>>
>
>Why?
>
>> The idea is simple:
>>
>> Put page on other nodes to the tail of pcp->lists[], because we
>> allocate from head and free from tail.
>>
>
>Pages from remote nodes are not placed on local lists. Even in the slab
>context, such objects are placed on alien caches which have special
>handling.
>
Hmm... I am not sure get your point correctly.
As I mentioned in the reply to Vlastimil, every zone has a
per_cpu_pageset for each cpu. For those per_cpu_pageset of one zone, it
will only contains pages from this zone. This means, some of
per_cpu_pageset will have the pages with the same node id, while others
not.
I don't get your point for the slab context. They use a different list
instead of pcp->lists[]? If you could give me some hint, I may catch up.
>> Since my desktop just has one numa node, I couldn't test the effect.
>
>I suspect it would eventually cause a crash or at least weirdness as the
>page zone ids would not match due to different nodes.
>
If my analysis is correct, there are only two relationship between page
node_id of those pages in pcp and the pcp's node_id, either the same or
not.
Let me have a try with qemu emulated numa system. :-)
>> Sorry for sending this without a real justification. Hope this will not
>> make you uncomfortable. I would be very glad if you suggest some
>> verifications that I could do.
>>
>> Below is my testing patch, look forward your comments.
>>
>
>I commend you trying to understand how the page allocator works but I
>suggest you take a step back, pick a workload that is of interest and
>profile it to see where hot spots are that may pinpoint where an
>improvement can be made.
>
>--
>Mel Gorman
>SUSE Labs
--
Wei Yang
Help you, Help me
next prev parent reply other threads:[~2018-10-20 16:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-19 4:33 Wei Yang
2018-10-19 8:38 ` Mel Gorman
2018-10-20 0:54 ` Wei Yang
2018-10-20 16:33 ` Wei Yang [this message]
2018-10-21 2:36 ` Wei Yang
2018-10-21 12:12 ` Mel Gorman
2018-10-22 1:24 ` Wei Yang
2018-10-19 13:43 ` Vlastimil Babka
2018-10-20 1:38 ` Wei Yang
2018-10-20 16:10 ` Wei Yang
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