Gentoo Archives: gentoo-amd64

From: Volker Armin Hemmann <volkerarmin@××××××××××.com>
To: gentoo-amd64@l.g.o
Subject: Re: [gentoo-amd64] Re: Memory usage; 32 bit vs 64 bit.
Date: Tue, 04 Jan 2011 13:02:49
In Reply to: [gentoo-amd64] Re: Memory usage; 32 bit vs 64 bit. by Duncan <>
On Tuesday 04 January 2011 09:12:17 Duncan wrote:
> Volker Armin Hemmann posted on Tue, 04 Jan 2011 08:27:28 +0100 as > > excerpted: > > swap kills interactivity and is really, really bad on linux. No matter > > how much you stripe it. Swap is a true horror. So setting swappiness to > > 100 (which means: keep caches alive, no matter what and swap the hell > > out of it) is a really bad idea. In my experience it is better to have a > > very low swappiness and let the kernel get the occasional data from > > disk, than to swap to the same disks. Strange eh? > > > > But better to wait 1.5s longer for konqueror to display a directory than > > to have a jerky mouse and input lag because of swap. Remember: the > > kernel ALWAYS swaps out the wrong stuff. > > I have swappiness at 60 - and back in the 4GB days at 0. Because swap > > sucks so much. > > > > You are not required to believe that. But just google. > > All I can go on is my experience, which agrees with you (and most of the > advice on the net) when it's a single-core CPU on single-spindle storage, > but I've found the experience rather different on multi-core machines > driving quad-spindle striped swap on mirrored RAID, with enough memory > swap usage is trivial in the ordinary case. Once swap usage hits half a > gig or so, yes, it's noticed, but until then, I literally don't normally > notice it unless/until I happen to see the usage reported on the system > monitors. > > OTOH, losing portage tree cache or news (nntp) article cache and having to > fetch the data from disk can be quite noticeable, as it DEFINITELY is the > first time I access after a reboot (the infamous cold-cache case), the > biggest reason I tend to leave the system running for weeks at a time, > rebooting only to load a new test kernel or the like. > > (FWIW, I use app-admin/lib_users to track programs using stale/already- > deleted libs after an update, and after quitting kde/X, restart daemons, > etc, to clear the list if necessary, thus clearing that source of both > security vulns and so-called anon-memory usage. I do use the > portage-2.2.0_alphas with preserve-libs, but use FEATURES=-preserve-libs > to avoid that source of bugs, so the old libs do normally get deleted.)
well, I don't waste electricity. I do have / on a ssd and /var with portage on a raifd5. And waiting a few seconds longer for emerge -auvDtn world to give results does not matter for me. But a stuck keyboard because of swapping? (swap striped to three disks, 4core processor) Inacceptable. And so swappiness has to stay down. Many days I don't even turn swap on. Seeing gcc oom is much less annoying than swap. It got better over the years but it is still far from being acceptable.