Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 1/3] Reintroduce zone_reclaim_interval for when zone_reclaim() scans and fails to avoid CPU spinning at 100% on NUMA | Date | Tue, 9 Jun 2009 18:45:29 +0900 (JST) |
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> > > Here it is just recording the jiffies value. The real smarts with the counter > > > use time_before() which I assumed could handle jiffie wrap-arounds. Even > > > if it doesn't, the consequence is that one scan will occur that could have > > > been avoided around the time of the jiffie wraparound. The value will then > > > be reset and it will be fine. > > > > time_before() assume two argument are enough nearly time. > > if we use 32bit cpu and HZ=1000, about jiffies wraparound about one month. > > > > Then, > > > > 1. zone reclaim failure occur > > 2. system works fine for one month > > 3. jiffies wrap and time_before() makes mis-calculation. > > > > And the scan occurs uselessly and zone_reclaim_failure gets set again. > I believe the one useless scan is not significant enough to warrent dealing > with jiffie wraparound.
Thank you for kindful explanation. I fully agreed.
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