> On Tue, 17 Nov 2009 16:17:50 +0900 (JST) > KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> wrote: > > > Non MM subsystem must not use PF_MEMALLOC. Memory reclaim need few > > memory, anyone must not prevent it. Otherwise the system cause > > mysterious hang-up and/or OOM Killer invokation. > > So now what happens if we are paging and all our memory is tied up for > writeback to a device or CIFS etc which can no longer allocate the memory > to complete the write out so the MM can reclaim ? Probably my answer is not so simple. sorry. reason1: MM reclaim does both dropping clean memory and writing out dirty pages. reason2: if all memory is exhausted, maybe we can't recover it. it is fundamental limitation of Virtual Memory subsystem. and, min-watermark is decided by number of system physcal memory, but # of I/O issue (i.e. # of pages of used by writeback thread) is mainly decided # of devices. then, we can't gurantee min-watermark is sufficient on any systems. Only reasonable solution is mempool like reservation, I think. IOW, any reservation memory shouldn't share unrelated subsystem. otherwise we lost any gurantee. So, I think we need to hear why many developer don't use mempool, instead use PF_MEMALLOC. > Am I missing something or is this patch set not addressing the case where > the writeback thread needs to inherit PF_MEMALLOC somehow (at least for > the I/O in question and those blocking it) Yes, probably my patchset isn't perfect. honestly I haven't understand why so many developer prefer to use PF_MEMALLOC. -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
