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    SubjectRe: [PATCH v2 RFC/RFT 0/5] Save single pages from CMA area
    On Wed, Mar 27, 2019 at 09:08:21AM +0100, Christoph Hellwig wrote:
    > On Tue, Mar 26, 2019 at 04:01:26PM -0700, Nicolin Chen wrote:
    > > This series of patches try to save single pages from CMA area bypassing
    > > all CMA single page alloctions and allocating normal pages instead, as
    > > all addresses within one single page are contiguous.
    > >
    > > We had once applied the PATCH-5 but reverted it as actually not all the
    > > callers handled the fallback allocations. Per Robin's suggestion, let's
    > > stuff alloc_pages()/free_page() fallbacks to those callers before having
    > > PATCH-5.
    >
    > Given the problems this has caused so far I'd like to see a good
    > explanation of why this optimization is so important that all the churn
    > is even worth it..

    With certain downstream user cases, we had run into a CMA exhaustion
    situation, and this was one of the changes that eased the problem. I
    have all the reasoning in the PATCH-5 commit message. And what Robin
    tested can also justify for it:
    https://lore.kernel.org/patchwork/patch/1004934/#1190139

    Thanks

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