Gentoo Archives: gentoo-amd64

From: Duncan <1i5t5.duncan@×××.net>
To: gentoo-amd64@l.g.o
Subject: [gentoo-amd64] Re: Memory usage; 32 bit vs 64 bit.
Date: Tue, 04 Jan 2011 10:02:50
In Reply to: Re: [gentoo-amd64] Re: Memory usage; 32 bit vs 64 bit. by Volker Armin Hemmann
Volker Armin Hemmann posted on Tue, 04 Jan 2011 08:27:28 +0100 as

> 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.) -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman


Subject Author
Re: [gentoo-amd64] Re: Memory usage; 32 bit vs 64 bit. Volker Armin Hemmann <volkerarmin@××××××××××.com>