Messages in this thread |  | | | Date | Mon, 16 Jul 2001 21:01:55 -0300 (BRT) | | From | Marcelo Tosatti <> | | Subject | Re: [PATCH] Separate global/perzone inactive/free shortage |
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On Mon, 16 Jul 2001, Kanoj Sarcar wrote:
> > --- Marcelo Tosatti <marcelo@conectiva.com.br> wrote: > > Hi, > > > > As well known, the VM does not make a distiction > > between global and > > per-zone shortages when trying to free memory. That > > means if only a given > > memory zone is under shortage, the kernel will scan > > pages from all zones. > > > > The following patch (against 2.4.6-ac2), changes the > > kernel behaviour to > > avoid freeing pages from zones which do not have an > > inactive and/or > > free shortage. > > > > Now I'm able to run memory hogs allocating 4GB of > > memory (on 4GB machine) > > without getting real long hangs on my ssh session. > > (which used to happen > > on stock -ac2 due to exhaustion of DMA pages for > > networking). > > > > Comments ? > > > > Dirk, Can you please try the patch and tell us if it > > fixes your problem ? > > > > > > Just a quick note. A per-zone page reclamation > method like this was what I had advocated and sent > patches to Linus for in the 2.3.43 time frame or so. > I think later performance work ripped out that work. > I guess the problem is that a lot of the different > page reclamation schemes first of all do not know > how to reclaim pages for a specific zone, and secondly > have to go thru a lot of work before they discover the > page they are trying to reclaim does not belong to the > shortage zone, hence wasting a lot of work/cputime. > try_to_swap_out is a good example, which can be solved > by rmaps.
Oh sure, rmaps would fix the performance problem caused by this. But I we dont have rmaps right now, and I doubt we want rmaps for 2.4.
Besides, the performance degradation of doing the perzone aging/deactivation this way is nothing compared to _not_ doing the thing on a perzone basis at all, IMHO.
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