On Sat, 3 Sep 2005 01:01, Pedro Venda wrote: > On Thursday 01 September 2005 14:18, Con Kolivas wrote: > > On Fri, 2 Sep 2005 00:18, Hans Kristian Rosbach wrote: > > > On Thu, 2005-09-01 at 23:46 +1000, Con Kolivas wrote: > > > > Here is a working swap prefetching patch for 2.6.13. I have > > > > resuscitated and rewritten some early prefetch code Thomas Schlichter > > > > did in late 2.5 to create a configurable kernel thread that reads in > > > > swap from ram in reverse order it was written out. It does this once > > > > kswapd has been idle for a minute (implying no current vm stress). > > > > This patch attached below is a rollup of two patches the current > > > > versions of which are here: > > > > > > That said, I have often thought it might be good to have something like > > > pre-writing swap, ie reverse what your patch does. > > > > > > In other words it'd keep as much of swappable data on disk as possible, > > > but without removing it from memory. So when it comes time to free up > > > some memory, the data is already on disk so no performance penalty from > > > writing it out. > > both ideas make all the sense to me. I'll give it a try, but in what way > can we test this kind of enhancement? maybe write a small program that > starts fills a good part of swap space and then, after 1min idle, 'watch > free -m' should show free memory decreasing (not counting cache/buffers) > with idle activity. decent?
Yes that about wraps up what it does. It would be even better used in a real world situation on a machine that has trouble "getting started" after an overnight updatedb run and has been idle for a while. > about the Hans's proposal - it would increase power consumption, because of > increased disk activity. about con's swap prefetch, I'm not so sure... Depends entirely on workload. Overall I think this increases power consumption because the disk does tiny little reads and keeps spinning until it has finished prefetching as much as it can. I was thinking it could be made configurable and to detect when laptop mode was enabled and so on... if it is thought that this is desirable of course. Cheers, Con - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
