Messages in this thread | | | Date | Tue, 22 Jun 2021 19:04:02 +0100 | From | Matthew Wilcox <> | Subject | Re: Do we need to unrevert "fs: do not prefault sys_write() user buffer pages"? |
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On Tue, Jun 22, 2021 at 06:55:33PM +0100, David Howells wrote: > Linus Torvalds <torvalds@linux-foundation.org> wrote: > > > End result: doing the fault_in_readable "unnecessarily" at the > > beginning is likely the better optimization. It's basically free when > > it's not necessary, and it avoids an extra fault (and extra > > lock/unlock and retry) when it does end up faulting pages in. > > It may also cause the read in to happen in the background whilst write_begin > is being done.
Huh? Last I checked, the fault_in_readable actually read a byte from the page. It has to wait for the read to complete before that can happen.
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