Messages in this thread | | | Date | Tue, 21 Aug 2001 00:58:32 -0300 (BRST) | From | Rik van Riel <> | Subject | Re: 2.4.8/2.4.9 VM problems |
| |
On Tue, 21 Aug 2001, Daniel Phillips wrote:
> I have to admit, the 100 FTP clients case wasn't on the top of my > mind. Even so, think about what is really happening. Nothing is > getting activated and nothing is competing with these allocations so
> Assuming that some of the files are more popular than others, these > file pages will be touched more than once and will go onto the active > ring, also exactly what you want.
... and so you contradict yourself in consecutive paragraphs...
> As they get old they get fed into the inactive queue at a rate that's > tunable. I don't see what the problem is.
You just pointed it out. The old pages get fed into the inactive queue at a rate which isn't influenced by how much pressure the new pages put on the VM, but only by some "tunable" rate.
> There are a couple of simple improvements that can be made. We could mark > all new pages referenced, age=1 (to distinguish from aged-to-zero pages). We > would not do unlazy activation but just allow age to increment with each > touch. Then, in addition to the Referenced test, we would test the age > against a tunable threshold to decide which pages to rescue. You can see > that this would take care of your 100 streaming clients case nicely, while > not negatively affecting the cases that are already working well.
Nice way to fuck up the 100 streaming client case even more, you mean.
> A second simple improvement is to have separate activation and deactivation > queues. This allows you to tune the rate at which pages are pulled from the > activation queue (these would be the streaming IO pages) against pages culled > from the active list. I can't think of any downside at all for doing this, > except that it's not something I'd consider appropriate for the 2.4 series.
This is called "better page aging".
> > [...] you haven't yet made any > > proposal on how to make the rest of the VM interact nicely > > with the use-once idea, preventing things like the thrashing > > of the readahead window, etc... > > This is hypothetical thrashing so far, have you see it in the wild?
Yes.
Rik -- IA64: a worthy successor to i860.
http://www.surriel.com/ http://distro.conectiva.com/
Send all your spam to aardvark@nl.linux.org (spam digging piggy)
- 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/
| |