On Wed, Jan 05, 2011 at 03:27:37PM -0600, Michael Roth wrote: > On 01/05/2011 02:35 PM, Andrea Arcangeli wrote: > > On Wed, Jan 05, 2011 at 02:26:19PM -0600, Michael Roth wrote: > >> Yah you're right, but I've seen several discussions about using mempath > >> for tmpfs/ram-backed files for things like numa/zram/etc so tend to > >> think of it as something potentially more than just a hook for > >> hugetlbfs, which is becoming less and less useful. But the MADV_DONTFORK > >> stuff should still be immediately applicable. > > > > Yes, MADV_DONTFORK should be set all on all guest physical memory > > without options so I hope the new patch I just posted is fine to stop > > the spurious -ENOMEM failures in fork. > > The patch in this thread? A couple paths still aren't covered when using > -mem-path. Something like this should get them all:
Well the reason of MADV_DONTFORK is to avoid accounting issues with anonymous memory, mem-path don't have that issue as hugetlbfs skips the accounting (it has to because hugetlbfs are not always taken from the regular page allocator). It could be however considered a minor performance optimization. Now you mention that you want to use -mem-path for other things too, so maybe that's why you need it there too. BTW, if you ever need it for more than hugetlbfs, I'm afraid this MAP_PRIVATE I see when mem_prealloc isn't set, is going to screw any other potential useful usage besides hugetlbfs, not exactly sure why it makes any sense to use MAP_PRIVATE there and not only MAP_SHARED.