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? -- Kirill A. Shutemov
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