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    SubjectRe: [PATCH]vmscan: handle underflow for get_scan_ratio
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    > On Tue, 2010-03-30 at 14:08 +0800, KOSAKI Motohiro wrote:
    > > Hi
    > >
    > > > Commit 84b18490d1f1bc7ed5095c929f78bc002eb70f26 introduces a regression.
    > > > With it, our tmpfs test always oom. The test has a lot of rotated anon
    > > > pages and cause percent[0] zero. Actually the percent[0] is a very small
    > > > value, but our calculation round it to zero. The commit makes vmscan
    > > > completely skip anon pages and cause oops.
    > > > An option is if percent[x] is zero in get_scan_ratio(), forces it
    > > > to 1. See below patch.
    > > > But the offending commit still changes behavior. Without the commit, we scan
    > > > all pages if priority is zero, below patch doesn't fix this. Don't know if
    > > > It's required to fix this too.
    > >
    > > Can you please post your /proc/meminfo
    > attached.
    > > and reproduce program? I'll digg it.
    > our test is quite sample. mount tmpfs with double memory size and store several
    > copies (memory size * 2/G) of kernel in tmpfs, and then do kernel build.
    > for example, there is 3G memory and then tmpfs size is 6G and there is 6
    > kernel copy.

    Wow, tmpfs size > memsize!


    > > Very unfortunately, this patch isn't acceptable. In past time, vmscan
    > > had similar logic, but 1% swap-out made lots bug reports.
    > can you elaborate this?
    > Completely restore previous behavior (do full scan with priority 0) is
    > ok too.

    This is a option. but we need to know the root cause anyway. if not,
    we might reintroduce this issue again in the future.





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