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    SubjectRe: [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA
    On Fri, 15 Feb 2019, Matthew Wilcox wrote:

    > > Since RDMA is something similar: Can we say that a file that is used for
    > > RDMA should not use the page cache?
    >
    > That makes no sense. The page cache is the standard synchronisation point
    > for filesystems and processes. The only problems come in for the things
    > which bypass the page cache like O_DIRECT and DAX.

    It makes a lot of sense since the filesystems play COW etc games with the
    pages and RDMA is very much like O_DIRECT in that the pages are modified
    directly under I/O. It also bypasses the page cache in case you have
    not noticed yet.

    Both filesysetms and RDMA acting on a page cache at
    the same time lead to the mess that we are trying to solve.


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