On Thu, 15 Nov 2012 11:41:55 +0200 "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> wrote: > On Wed, Nov 14, 2012 at 03:37:09PM -0800, David Rientjes wrote: > > On Wed, 7 Nov 2012, Kirill A. Shutemov wrote: > > > > > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> > > > > > > Instead of allocating huge zero page on hugepage_init() we can postpone it > > > until first huge zero page map. It saves memory if THP is not in use. > > > > > > > Is it worth the branch on every non-write pagefault after that? The > > unlikely() is not going to help on x86. If thp is enabled in your > > .config (which isn't the default), then I think it's better to just > > allocate the zero huge page once and avoid any branches after that to > > lazily allocate it. (Or do it only when thp is set to "madvise" or > > "always" if booting with transparent_hugepage=never.) > > I can rewrite the check to static_key if you want. Would it be better? The new test-n-branch only happens on the first read fault against a thp huge page, yes? In which case it's a quite infrequent event and I suspect this isn't worth bothering about. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>