>-----Original Message----- >From: Russell King - ARM Linux [mailto:linux@xxxxxxxxxxxxxxxx] >Sent: 2013年8月1日 16:57 >To: Lisa Du >Cc: KOSAKI Motohiro; Christoph Lameter; linux-mm@xxxxxxxxx; Mel >Gorman; Bob Liu; Neil Zhang >Subject: Re: Possible deadloop in direct reclaim? > >On Wed, Jul 31, 2013 at 10:19:53PM -0700, Lisa Du wrote: >> >fork alloc order-1 memory for stack. Where and why alloc order-2? If it is >> >arch specific code, please >> >contact arch maintainer. >> Yes arch do_fork allocate order-2 memory when copy_process. >> Hi, Russel >> What's your opinion about this question? >> If we really need order-2 memory for fork, then we'd better set >> CONFIG_COMPATION right? > >Well, I gave up trying to read the original messages because the quoting >style is a total mess, so I don't have a full understanding of what the >issue is. I'm really sorry for my quoting style, I'll avoid such issue in future! > >However, we have always required order-2 memory for fork, going back to >the 1.x kernel days - it's fundamental to ARM to have that. The order-2 >allocation os for the 1st level page table. No order-2 allocation, no >page tables for the new thread. > >Looking at this commit: > >commit 05106e6a54aed321191b4bb5c9ee09538cbad3b1 >Author: Rik van Riel <riel@xxxxxxxxxx> >Date: Mon Oct 8 16:33:03 2012 -0700 > > mm: enable CONFIG_COMPACTION by default > > Now that lumpy reclaim has been removed, compaction is the only >way left > to free up contiguous memory areas. It is time to just enable > CONFIG_COMPACTION by default. > >it seems to indicate that everyone should have this enabled - however, >the way the change has been done, anyone building from defconfigs before >that change will not have that option enabled. > >So yes, this option should be turned on. Thanks Russel! I think I have got the information I want. Really appreciate for your explanation! ?韬{.n???檩jg???a?旃???)钋???骅w+h?璀?ｙ/i?⒏??⒎???Щ ??m?? ?)钋???痂?^??觥??ザ?v???O璁?f??i?⒏?