Messages in this thread | | | Date | Mon, 29 Jul 2002 11:32:56 -0700 | From | Andrew Morton <> | Subject | Re: [BK PATCH 2.5] Introduce 64-bit versions of PAGE_{CACHE_,}{MASK,ALIGN} |
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Russell King wrote: > > On Sun, Jul 28, 2002 at 05:10:48PM -0700, Andrew Morton wrote: > > - Remove ->virtual, do page_address() via a hash. 4(ish) bytes saved. > > Hmmmmmmm. page_address() is already 5 loads (on ARM) if page->virtual > isn't used. I'm seriously considering changing page_address() to cover > the 3 cases more efficiently:
Well, one would want to keep the WANT_PAGE_VIRTUAL thing anyway.
btw, the usage of page_address() will quite possibly drop sharply soon anyway. There's the patch floating about which permits atomic kmaps to be held across copy_*_user. If that is adopted, things like the pagecache IO routines won't do page_address() any more.
Said patch speeds up pagecache IO by between 0% and probably 30%. It's the mystery surrounding this variation which is holding things up.
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