[lkml]   [2014]   [Feb]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC PATCH V5] mm readahead: Fix readahead fail for no local memory and limit readahead pages
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.

 \ /
  Last update: 2014-02-07 01:21    [W:0.081 / U:0.596 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site