Re: [PATCH]vmscan: handle underflow for get_scan_ratio

[KOSAKI Motohiro]

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 and reproduce program? I'll digg it.

Very unfortunately, this patch isn't acceptable. In past time, vmscan 
had similar logic, but 1% swap-out made lots bug reports. 



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