(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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>