On Wed, Mar 23, 2011 at 11:36 PM, Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote: > On Wed, Mar 23, 2011 at 03:01:33PM +0900, Minchan Kim wrote: >> Okay. I will look at result. >> If the problem happens again with reverted patch of page_alloc.c, >> Don't we have to investigate further the problem happens with SLUB or >> some driver's big memory allocation which is lower than 2M? We didn't >> see the problem allocation under 2M but async migration's history was >> short so we can't make sure it. > > Yes, probably. This is also why I hope the page_alloc.c part didn't > make a difference. We kept it to be sure to make any sign of sync > migration to go away from the stack traces, but I hope it's not so > important anymore now. Reclaim eventually also becomes synchronous. > >> Don't you want to add async migration for low order allocation like SLUB? >> If you don't want to do async migration low order allocation, we can >> add the check if (gfp_flags & __GFP_RETRY) && (order >= 9 or some >> threshold) for async migration? >> >> My point is to avoid implicit hidden meaning of __GFP_NO_KSWAPD >> although __GFP_REPEAT already does it. > > I see your point, so let's think about it after testing of the > reversal of the page_alloc.c change. If that's not necessary we just > reverse it and it already solves these concerns. Absolutely. > >> If async migration is going on and meet the dirty page, the patch can >> return the -EBUSY so the page could put back to head of LRU but the >> old migration can be going on although the page is dirty. > > Ok, but in term of LRU it's not like we're going to help much in > skipping the page in compaction, it'd leave the sync pages there, and > only list_del the async pages. I think it's mostly a cpu saving > optimization, I doubt the lru ordering will be much more accurate by > not doing list_del on the sync pages considering we would list_del > the rest but not the sync part. Yes. In terms of all LRU pages, I doubt it but isn't it better than current meaningless rotation if we can do it easily? Anyway, It's not a urgent issue so I don't mind it. :) Thanks. -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx 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>