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    SubjectRe: O_DIRECT question
    On Thu, 11 Jan 2007, Linus Torvalds wrote:

    > On Thu, 11 Jan 2007, Viktor wrote:
    > >
    > > OK, madvise() used with mmap'ed file allows to have reads from a file
    > > with zero-copy between kernel/user buffers and don't pollute cache
    > > memory unnecessarily. But how about writes? How is to do zero-copy
    > > writes to a file and don't pollute cache memory without using O_DIRECT?
    > > Do I miss the appropriate interface?
    > mmap()+msync() can do that too.
    > Also, regular user-space page-aligned data could easily just be moved into
    > the page cache. We actually have a lot of the infrastructure for it. See
    > the "splice()" system call.

    it seems to me that if splice and fadvise and related things are
    sufficient for userland to take care of things "properly" then O_DIRECT
    could be changed into splice/fadvise calls either by a library or in the
    kernel directly...

    looking at the splice(2) api it seems like it'll be difficult to implement
    O_DIRECT pread/pwrite from userland using splice... so there'd need to be
    some help there.

    i'm probably missing something.

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      Last update: 2007-01-12 09:29    [W:0.020 / U:31.156 seconds]
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