Messages in this thread Patch in this message | | | Date | Tue, 30 Mar 2010 19:17:17 +0900 | Subject | Re: [PATCH]vmscan: handle underflow for get_scan_ratio | From | Minchan Kim <> |
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On Tue, Mar 30, 2010 at 2:53 PM, Shaohua Li <shaohua.li@intel.com> wrote: > 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. > > Signed-off-by: Shaohua Li <shaohua.li@intel.com> > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 79c8098..d5cc34e 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1604,6 +1604,18 @@ static void get_scan_ratio(struct zone *zone, struct scan_control *sc, > /* Normalize to percentages */ > percent[0] = 100 * ap / (ap + fp + 1); > percent[1] = 100 - percent[0]; > + /* > + * if percent[x] is small and rounded to 0, this case doesn't mean we > + * should skip scan. Give it at least 1% share. > + */ > + if (percent[0] == 0) { > + percent[0] = 1; > + percent[1] = 99; > + } > + if (percent[1] == 0) { > + percent[0] = 99; > + percent[1] = 1; > + } > } > > /* >
Yes. It made subtle change. But we should not depend that change. Current logic seems to be good and clear than old. I think you were lucky at that time by not-good and not-clear logic.
BTW, How about this?
diff --git a/mm/vmscan.c b/mm/vmscan.c index 79c8098..f0df563 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1646,11 +1646,6 @@ static void shrink_zone(int priority, struct zone *zone, int file = is_file_lru(l); unsigned long scan;
- if (percent[file] == 0) { - nr[l] = 0; - continue; - } - scan = zone_nr_lru_pages(zone, sc, l); if (priority) { scan >>= priority;
-- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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