(4/8/13 1:32 PM), Cody P Schafer wrote:On 04/07/2013 08:39 AM, KOSAKI Motohiro wrote:(4/5/13 4:33 PM), Cody P Schafer wrote:No off-cpu users of the percpu pagesets exist.
zone_pcp_update()'s goal is to adjust the ->high and ->mark members of a
percpu pageset based on a zone's ->managed_pages. We don't need to drain
the entire percpu pageset just to modify these fields. Avoid calling
setup_pageset() (and the draining required to call it) and instead just
set the fields' values.
This does change the behavior of zone_pcp_update() as the percpu
pagesets will not be drained when zone_pcp_update() is called (they will
end up being shrunk, not completely drained, later when a 0-order page
is freed in free_hot_cold_page()).
Signed-off-by: Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx>
NAK.
1) zone_pcp_update() is only used from memory hotplug and it require page drain.
I'm looking at this code because I'm currently working on a patchset
which adds another interface which modifies zone sizes, so "only used
from memory hotplug" is a temporary thing (unless I discover that
zone_pcp_update() is not intended to do what I want it to do).
maybe yes, maybe no. I don't know temporary or not. However the fact is,
you must not break anywhere. You need to look all caller always.
2) stop_machin is used for avoiding race. just removing it is insane.
What race? Is there a cross cpu access to ->high & ->batch that makes
using on_each_cpu() instead of stop_machine() inappropriate? It is
absolutely not just being removed.
OK, I missed that. however your code is still wrong.
However you can't call free_pcppages_bulk() from interrupt context and
then you can't use on_each_cpu() anyway.