Messages in this thread | | | Date | Tue, 14 Sep 2004 18:41:58 -0300 | From | Marcelo Tosatti <> | Subject | Re: swapping and the value of /proc/sys/vm/swappiness |
| |
On Wed, Sep 15, 2004 at 08:53:21AM +1000, Con Kolivas wrote: > Marcelo Tosatti wrote: > >On Tue, Sep 14, 2004 at 11:31:53AM -0700, Florin Andrei wrote: > > > >>On Mon, 2004-09-06 at 16:27, Andrew Morton wrote: > >> > >>>Con Kolivas <kernel@kolivas.org> wrote: > >> > >>>>The change was not deliberate but there have been some other people > >>>>report significant changes in the swappiness behaviour as well (see > >>>>archives). It has usually been of the increased swapping variety > >>>>lately. It has been annoying enough to the bleeding edge desktop users > >>>>for a swag of out-of-tree hacks to start appearing (like mine). > >>> > >>>All of which is largely wasted effort. > >> > >>>From a highly-theoretical, ivory-tower perspective, maybe; i am not the > >>one to pass judgement. > >>>From a realistic, "fix it 'cause it's performing worse than MSDOS > >>without a disk cache" perspective, definitely not true. > >> > >>I've found a situation where the vanilla kernel has a behaviour that > >>makes no sense: > >> > >>http://marc.theaimsgroup.com/?l=linux-kernel&m=109237941331221&w=2 > >>http://marc.theaimsgroup.com/?l=linux-kernel&m=109237959719868&w=2 > >>http://marc.theaimsgroup.com/?l=linux-kernel&m=109238126314192&w=2 > >> > >>A patch by Con Kolivas fixed it: > >> > >>http://marc.theaimsgroup.com/?l=linux-kernel&m=109410526607990&w=2 > >> > >>I cannot offer more details, i have no time for experiments, i just need > >>a system that works. The vanilla kernel does not. > > > > > >Have you tried to decrease the value of /proc/sys/vm/swappiness > >to say 30 and see what you get? > > > >Andrew's point is that we should identify the problem - Con's patch > >rewrites swapping policy. > > I already answered this. That hard swappiness patch does not really > rewrite swapping policy. It identifies exactly what has changed because > it does not count "distress in the swap tendency". Therefore if the > swappiness value is the same, the mapped ratio is the same (in the > workload) yet the vm is swappinig more, it is getting into more > "distress". The mapped ratio is the same but the "distress" is for some > reason much higher in later kernels, meaning the priority of our > scanning is getting more and more intense. This should help direct your > searches.
> These are the relevant lines of code _from mainline_: > > distress = 100 >> zone->prev_priority > mapped_ratio = (sc->nr_mapped * 100) / total_memory; > swap_tendency = mapped_ratio / 2 + distress + vm_swappiness > if (swap_tendency >= 100) > - reclaim_mapped = 1; > > > That hard swappiness patch effectively made "distress == 0" always.
OK.
So isnt it true that decreasing vm_swappiness should compensate distress and have the same effect of your patch?
To be fair I'm just arguing, haven't really looked at the code.
- 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/
| |