Messages in this thread | | | Date | Sun, 11 Feb 2001 08:43:09 +0100 (CET) | From | Mike Galbraith <> | Subject | Re: Linux 2.4.1-ac7 |
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On Sat, 10 Feb 2001, Rik van Riel wrote:
> On Sat, 10 Feb 2001, Mike Galbraith wrote: > > On Sat, 10 Feb 2001, Rik van Riel wrote: > > > On Sat, 10 Feb 2001, Marcelo Tosatti wrote: > > > > On Sat, 10 Feb 2001, Mike Galbraith wrote: > > > > > > > > > This change makes my box swap madly under load. > > > > > > > > Swapped out pages were not being counted in the flushing limitation. > > > > > > > > Could you try the following patch? > > > > > > Marcelo's patch should do the trick wrt. to making page_launder() > > > well-behaved again. It should fix the problems some people have > > > seen with bursty swap behaviour. > > > > It's still reluctant to shrink cache. I'm hitting I/O saturation > > at 20 jobs vs 30 with ac5. (difference seems to be the delta in > > space taken by cache.. ~same space shows as additional swap volume). > > Indeed, to "fix" that we'll need to work at refill_inactive().
If this reluctance to munch cache can be relaxed a little, I think we'll see the end of a long standing problem. I often see a scenario wherein we flush everything flushable, then steal the entire cache before doing any paging. The result (we hit a wall) is a mondo swapout followed immediately by swapping it all right back in. We seem to have done a complete turnaround wrt paging vs flush/cache reap preference, and that does effectively cure this scenario.. but methinks optimal (-ENOENT?) lies somewhere in between.
> However, I am very much against tuning the VM for one particular > workload. If you can show me that this problem also happens under > other workloads we can work at changing it, but I don't think it's > right to optimise the VM for a specific workload...
I'll watch behavior under other loads. (I don't have enough network capacity to do anything stressful there, and whatever load I pick has to be compute bound as to not end up benchmarking my modest I/O capacity.. suggestions welcome. I use make -j primarily because it doesn't need much I/O bandwidth for itself, but does allocate quite a bit.. that leaves most I/O capacity free for vm usage)
Something else I see while watching it run: MUCH more swapout than swapin. Does that mean we're sending pages to swap only to find out that we never need them again?
-Mike
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