On Fri, 2011-07-29 at 23:40 +0800, Mel Gorman wrote: > On Fri, Jul 29, 2011 at 11:23:10PM +0800, Alex Shi wrote: > > In commit 215ddd66, Mel Gorman said kswapd is better to sleep after a > > unsuccessful balancing if there is tighter reclaim request pending in > > the balancing. In this scenario, the 'order' and 'classzone_idx' > > that are checked for tighter request judgment is incorrect, since they > > aren't the one kswapd should read from new pgdat, but the last time pgdat > > value for just now balancing. Then kswapd will skip try_to_sleep func > > and rebalance the last pgdat request. It's not our expected behavior. > > > > So, I added new variables to distinguish the returned order/classzone_idx > > from last balancing, that can resolved above issue in that scenario. > > > > I'm afraid this changelog is very difficult to read and I do not see > what problem you are trying to solve and I do not see what this patch > might solve. > > When balance_pgdat() returns with a lower classzone or order, the values > stored in pgdat are not re-read and instead it tries to go to sleep > based on the starting request. Something like; Thanks for your comments, I will use this comments style next time, list request A, B etc. > > 1. Read pgdat request A (classzone_idx, order) Assume the order of A > 0, like is 3. > 2. balance_pgdat() > 3. During pgdat, a new pgdat request B (classzone_idx, order) is placed > 4. balance_pgdat() returns but failed so classzone_idx is lower Another balance_pgdat() failure indicate is returned order == 0, am I right? If so, the next step of kswapd is not trying to sleep, but do request A balance again. And I thought this behavior doesn't match the comments in kswapd. > 5. Try to sleep based on pgdat request A > > i.e. pgdat request B is not read and there is a comment explaining > why pgdat request B is not read after balance_pgdat() fails. > > This patch adds some variables that might improve the readability > for some people but otherwise I can't see what problem is being > fixed. What did I miss? > -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>