On Mon, Jul 01, 2024 at 11:22:24PM -0700, Andrew Morton wrote: >On Tue, 2 Jul 2024 02:09:31 +0000 Wei Yang <richard.weiyang@xxxxxxxxx> wrote: > >> The prefetchw() is introduced from an ancient patch[1]. >> >> The change log says: >> >> The basic idea is to free higher order pages instead of going >> through every single one. Also, some unnecessary atomic operations >> are done away with and replaced with non-atomic equivalents, and >> prefetching is done where it helps the most. For a more in-depth >> discusion of this patch, please see the linux-ia64 archives (topic >> is "free bootmem feedback patch"). >> >> So there are several changes improve the bootmem freeing, in which the >> most basic idea is freeing higher order pages. And as Matthew says, >> "Itanium CPUs of this era had no prefetchers." >> >> I did 10 round bootup tests before and after this change, the data >> doesn't prove prefetchw() help speeding up bootmem freeing. The sum of >> the 10 round bootmem freeing time after prefetchw() removal even 5.2% >> faster than before. > >I don't think I've ever seen prefetch make a damn bit of difference. > >> [1]: https://lore.kernel.org/linux-ia64/40F46962.4090604@xxxxxxx/ >> >> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx> >> Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> >> CC: David Hildenbrand <david@xxxxxxxxxx> >> >> --- >> The patch is based on mm-stable with David's change. > >Oh help. David makes many changes. Please identify patches with much >care. Fully quoting the email title works, as does a link. > The commit is 3dadec1babf9eee0c67c967df931d6f0cb124a04 mm: pass meminit_context to __free_pages_core() The link is, if I am correct. https://lore.kernel.org/all/20240607090939.89524-2-david@xxxxxxxxxx/ BTW, how we track the mail link? Just search in lore.kernel.org? -- Wei Yang Help you, Help me
