[lkml]   [2019]   [Feb]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC PATCH 01/31] mm: migrate: Add exchange_pages to exchange two lists of pages.

On 02/19/2019 06:26 PM, Matthew Wilcox wrote:
> On Tue, Feb 19, 2019 at 01:12:07PM +0530, Anshuman Khandual wrote:
>> But the location of this temp page matters as well because you would like to
>> saturate the inter node interface. It needs to be either of the nodes where
>> the source or destination page belongs. Any other node would generate two
>> internode copy process which is not what you intend here I guess.
> That makes no sense. It should be allocated on the local node of the CPU
> performing the copy. If the CPU is in node A, the destination is in node B
> and the source is in node C, then you're doing 4k worth of reads from node C,
> 4k worth of reads from node B, 4k worth of writes to node C followed by
> 4k worth of writes to node B. Eventually the 4k of dirty cachelines on
> node A will be written back from cache to the local memory (... or not,
> if that page gets reused for some other purpose first).
> If you allocate the page on node B or node C, that's an extra 4k of writes
> to be sent across the inter-node link.

Thats right there will be an extra remote write. My assumption was that the CPU
performing the copy belongs to either node B or node C.

 \ /
  Last update: 2019-02-20 05:39    [W:0.088 / U:9.792 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site