From: Blaisorblade <bla...@ya...> - 2005-12-11 16:18:21
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On Thursday 08 December 2005 18:01, Jeff Dike wrote: > On Thu, Dec 08, 2005 at 03:06:28PM +0100, Joel Palmius wrote: > > Are there any general recommendations for making throughput on UBDs more > > efficient? Such as kernel settings, recommended filesystems..? > > > > Doing an "emerge sync" inside an uml raises iowait to 100% and load to 7, > > making the machine more or less inaccessible. Just wondering if it's me > > having bad settings. > > I strongly suspect a bad interaction with the host I/O scheduler, although > I can't prove anything. One OLS paper talked about using a special host elevator (without adding details), together with XFS on the host partition containing UBD files (because XFS is optimized for huge files), to better support UML's AIO. > The UML is just passing read/write requests to the > host and expecting them to be handled somewhat efficiently. > Using AIO helps (~25% on a kernel build), but I still see the same basic > symptoms (nothing running, everything in iowait). Tested with a CPU-hog running too? That's the test case we're interested into to see whether UML is performing blocking I/O calls or not. Also, the iowait is on the host or on the guest? I fear on the host, but I'd hope not. -- Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!". Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894) http://www.user-mode-linux.org/~blaisorblade ___________________________________ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it |