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    SubjectRe: [Stable-review] [08/45] mm, x86: Saving vmcore with non-lazy freeing of vmas
    On Fri, 2010-11-19 at 13:42 -0800, Greg KH wrote:
    > 2.6.32-stable review patch. If anyone has any objections, please let us know.
    >
    > ------------------
    >
    > From: Cliff Wickman <cpw@sgi.com>
    >
    > commit 3ee48b6af49cf534ca2f481ecc484b156a41451d upstream.
    >
    > During the reading of /proc/vmcore the kernel is doing
    > ioremap()/iounmap() repeatedly. And the buildup of un-flushed
    > vm_area_struct's is causing a great deal of overhead. (rb_next()
    > is chewing up most of that time).
    >
    > This solution is to provide function set_iounmap_nonlazy(). It
    > causes a subsequent call to iounmap() to immediately purge the
    > vma area (with try_purge_vmap_area_lazy()).
    >
    > With this patch we have seen the time for writing a 250MB
    > compressed dump drop from 71 seconds to 44 seconds.
    [...]

    Useful, but it doesn't seem to meet the criteria for stable updates.

    Ben.

    --
    Ben Hutchings
    Once a job is fouled up, anything done to improve it makes it worse.
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