On 01/28/2011 01:24 PM, Andrea Arcangeli wrote:
On Fri, Jan 28, 2011 at 01:03:50PM -0500, Rik van Riel wrote:
My point is, the behaviour you describe would be WRONG :)
The reason is that the different zones can contain data
that is either heavily used or rarely used, often some
mixture of the two, but sometimes the zones are out of
balance in how much the data in memory gets touched.
We need to reclaim and reuse the lightly used memory
a little faster than the heavily used memory, to even
out the memory pressure between zones.
I've no idea how kswapd can reclaim the lightly used memory a little
faster when it blocks at high+gap.
It will block at high+gap only when one zone has really
easily reclaimable memory, and another zone has difficult
to free memory.
That creates a free memory differential between the
easy to free and difficult to free memory zones.
If memory in all zones is equally easy to free, kswapd
will go to sleep once the high watermark is reached in
every zone.
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