On Tue, Jun 01, 2010 at 06:20:25PM +0200, Andi Kleen wrote: > On Wed, Jun 02, 2010 at 01:59:43AM +1000, Nick Piggin wrote: > > On Tue, Jun 01, 2010 at 05:48:10PM +0200, Andi Kleen wrote: > > > Nick Piggin <npiggin@xxxxxxx> writes: > > > > > > > This isn't really a new problem, and I don't know how important it is, > > > > but I recently came across it again when doing some aim7 testing with > > > > huge numbers of tasks. > > > > > > Seems reasonable. Of course you need to at least > > > save/restore the old CPU policy, and use a subset of it. > > > > The mpolicy? My patch does that (mpol_prefer_cpu_start/end). The real > > problem is that it can actually violate the parent's mempolicy. For > > example MPOL_BIND and cpus_allowed set on a node outside the mempolicy. > > I don't see where you store 'old', but maybe I missed it. It's the argument returned by mpol_prefer_cpu_start. Yes this also opens races for lost-write when we have concurrent mpol changes. So I'm not claiming the code is right. > > > slightly more difficult. The advantage would be that on multiple > > > migrations it would follow. And it would be a bit slower for > > > the initial case. > > > > Migrate what on touch? Talking mainly about kernel memory structures, > > task_struct, mm, vmas, page tables, kernel stack, etc. > > Migrate task_struct, mm, vmas, page tables, kernel stack > on reasonable touch. As long as they are not shared it shouldn't > be too difficult. Possible but that's a lot further off (considering we don't even migrate user memory) and is complimentary to this patch. -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>