Messages in this thread | | | From | Denis Vlasenko <> | Subject | Re: [PATCH] add a clear_pages function to clear pages of higher order | Date | Fri, 11 Mar 2005 10:08:11 +0200 |
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On Friday 11 March 2005 03:03, Christoph Lameter wrote: > Changelog: > - use Kconfig and CONFIG_CLEAR_PAGES > > The zeroing of a page of a arbitrary order in page_alloc.c and in hugetlb.c may benefit from a > clear_page that is capable of zeroing multiple pages at once. The following patch adds > a function "clear_pages" that is capable of clearing multiple continuous pages at once. > > Patch against 2.6.11-bk6 > > Signed-off-by: Christoph Lameter <clameter@sgi.com> [snip] > -clear_page_end: > +clear_pages_end: > > /* C stepping K8 run faster using the string instructions. > It is also a lot simpler. Use this when possible */
Andi Kleen (iirc) says that non-temporal stores seem to be big win in microbenchmarks (and I second that), but they are a net loss when we are going to use zeroed page just after zeroing. He recommends avoid using non-temporal stores
With this new page prezeroing infrastructure, that argument most likely is not right anymore. Especially clearing of high-order pages definitely will benefit from NT stores because they do not kill L1 data cache in the process.
I don't have K8 and therefore cannot be 100% sure, but I really doubt that K8 optimize "rep stosq" into _NT_ stores.
Andi? -- vda
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