On Tue, 18 Feb 2014, [email protected] wrote: > From: Rik van Riel <[email protected]> > > The NUMA scanning code can end up iterating over many gigabytes > of unpopulated memory, especially in the case of a freshly started > KVM guest with lots of memory. > > This results in the mmu notifier code being called even when > there are no mapped pages in a virtual address range. The amount > of time wasted can be enough to trigger soft lockup warnings > with very large KVM guests. > > This patch moves the mmu notifier call to the pmd level, which > represents 1GB areas of memory on x86-64. Furthermore, the mmu > notifier code is only called from the address in the PMD where > present mappings are first encountered. > > The hugetlbfs code is left alone for now; hugetlb mappings are > not relocatable, and as such are left alone by the NUMA code, > and should never trigger this problem to begin with. > > Signed-off-by: Rik van Riel <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Andrea Arcangeli <[email protected]> > Reported-by: Xing Gang <[email protected]> > Tested-by: Chegu Vinod <[email protected]>
Acked-by: David Rientjes <[email protected]> Might have been cleaner to move the mmu_notifier_invalidate_range_{start,end}() to hugetlb_change_protection() as well, though. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
