Messages in this thread | | | Date | Thu, 29 Apr 2004 11:51:16 -0500 | From | Andy Isaacson <> | Subject | Re: ~500 megs cached yet 2.6.5 goes into swap hell |
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On Wed, Apr 28, 2004 at 08:19:24PM -0700, Andrew Morton wrote: > What you discuss above is just an implementation detail. Forget it. What > are the requirements? Thus far I've seen > > a) updatedb causes cache reclaim > > b) updatedb causes swapout > > c) prefer that openoffice/mozilla not get paged out when there's heavy > pagecache demand. > > For a) we don't really have a solution. Some have been proposed but they > could have serious downsides. > > For b) and c) we can tune the pageout-vs-cache reclaim tendency with > /proc/sys/vm/swappiness, only nobody seems to know that. > > What else is there?
What I want is for purely sequential workloads which far exceed cache size (dd, updatedb, tar czf /backup/home.nightly.tar.gz /home) to avoid thrashing my entire desktop out of memory. I DON'T CARE if the tar completed in 45 minutes rather than 80. (It wouldn't, anyways, because it only needs about 5 MB of cache to get every bit of the speedup it was going to get.) But the additional latency when I un-xlock in the morning is annoying, and there is no benefit.
For a more useful example, ideally I *should not be able to tell* that "dd if=/hde1 of=/hdf1" is running. [1] There is *no* benefit to cacheing more than about 2 pages, under this workload. But with current kernels, IME, that workload results in a gargantuan buffer cache and lots of swapout of apps I was using 3 minutes ago. I've taken to walking away for some coffee, coming back when it's done, and "sudo swapoff /dev/hda3; sudo swapon -a" to avoid the latency that is so annoying when trying to use bloaty apps.
[1] obviously I'll see some slowdown due to interrupts and PCI bandwidth; that's not what I'm railing against, here.
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