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    SubjectRe: [PATCH] swap: send callback when swap slot is freed
    On 08/13/2009 04:18 AM, Hugh Dickins wrote:
    > On Wed, 12 Aug 2009, Nitin Gupta wrote:
    >> Currently, we have "swap discard" mechanism which sends a discard bio request
    >> when we find a free cluster during scan_swap_map(). This callback can come a
    >> long time after swap slots are actually freed.
    >> This delay in callback is a great problem when (compressed) RAM [1] is used
    >> as a swap device. So, this change adds a callback which is called as
    >> soon as a swap slot becomes free. For above mentioned case of swapping
    >> over compressed RAM device, this is very useful since we can immediately
    >> free memory allocated for this swap page.
    >> This callback does not replace swap discard support. It is called with
    >> swap_lock held, so it is meant to trigger action that finishes quickly.
    >> However, swap discard is an I/O request and can be used for taking longer
    >> actions.
    >> Links:
    >> [1]
    > Please keep this with compcache for the moment (it has no other users).

    Oh, I missed this one.

    This small patch can be considered as first step for merging compcache
    to mainline :) Actually, it requires callbacks for swapon, swapoff too
    but that, I think, should be done in a separate patches.

    BTW, last time compcache was not accepted due to lack of performance
    numbers. Now the project has lot more data for various cases:
    Still need to collect data for worst-case behaviors and such...


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      Last update: 2009-08-13 04:43    [W:0.020 / U:12.264 seconds]
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