Re: mmap vs fs cache

From: Chris Friesen
Date: Fri Mar 08 2013 - 09:48:51 EST


On 03/08/2013 03:40 AM, Howard Chu wrote:

There is no way that a process that is accessing only 30GB of a mmap
should be able to fill up 32GB of RAM. There's nothing else running on
the machine, I've killed or suspended everything else in userland
besides a couple shells running top and vmstat. When I manually
drop_caches repeatedly, then eventually slapd RSS/SHR grows to 30GB and
the physical I/O stops.

Is it possible that the kernel is doing some sort of automatic readahead, but it ends up reading pages corresponding to data that isn't ever queried and so doesn't get mapped by the application?

Chris
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