From: Matthew B. <ma...@by...> - 2003-12-08 22:24:00
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=2D----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Monday 08 December 2003 19:01, Jeff Dike wrote: > As far as I'm concerned, this is papering over the symptoms rather than > fixing a real problem. > > If you're really not overselling memory, then the host should not be > swapping. If it is, then that's the problem. Hi Jeff, I don't think this is true. The 2.4 kernel does appear to swap ou= t=20 applications when (e.g.) a large file copy is underway, and the 2.6 kernel= =20 has been tweaked to get around this problem: http://kerneltrap.org/node/view/1044 We've not had enough time to try 2.6 on a production server as a host kerne= l,=20 but I'd be interested if you did know a way of tweaking a 2.4 host kernel t= o=20 guarantee RAM-locked pages to user-mode kernels; Matt Ayres mentioned "some= =20 interactivity and vm patches", could you elaborate on that please Matt? Fo= r=20 various reasons, we use a Redhat 2.4.20 kernel which I believe has had its= =20 memory management fiddled with. I like the sound of the more dynamic memory arrangement and manager daemon = for=20 UMLs, sounds like a good way to squeeze more customers onto a host machine.= =20 But if for the moment the only thing it should do is to keep the host from= =20 swapping, I know from a few our customers that mlocking has given more=20 predictable behaviour from guest kernels, especially if the host load spike= s=20 for a few minutes. That's my only argument as to why it should be included= :=20 mlocked kernels behave more predictably in a hosting environment! But=20 obviously I'm biased; if I can get the same effect without the patch on a 2= =2E4=20 host kernel I'd agree it's moot. =2D --=20 Matthew Bloch Bytemark Hosting tel. +44 (0) 8707 455026 http://www.bytemark-hosting.co.uk/ Dedicated Linux hosts from 15ukp ($26) per month =2D----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.3 (GNU/Linux) iD8DBQE/1Pn5T2rVDg8aLXQRAuMmAJ9BXfBodQcUX2AMPUfHdrKAtKTSMgCcCBc1 MI6K3OJQUdG1uqvzKq8MOMw=3D =3DZip4 =2D----END PGP SIGNATURE----- |