Jermey, I tought you wrote this, http://lists.freebsd.org/pipermail/freebsd-hackers/2007-February/019666.html.
Try GEOM Cache(gcache). It will be like, $ gcache create temp -s <size> /dev/XXYsZ $ dump <options> /dev/cache/temp <...> It's been 9 months since I tested so I don't remember about the detail numbers. However, I think it reduced user-time with dump to a half. I only wish gcache creates devices with .cache suffix like /dev/XXYsZ.cache. The cache cannot be shared among other providers anyway, it looks suffix style is more appropriate. Regards, Hiro On Sun, 11 Jan 2009 15:17:10 +1100 Peter Jeremy <[email protected]> wrote: > On 2009-Jan-09 09:50:27 -0700, "M. Warner Losh" <[email protected]> wrote: > >The read kBps was 3x the write kBps. > ... > >Any ideas what gives? I observed this with 16MB cache and with 32MB > >cache, fwiw. > > I've seen this as well. AFAIK, this is a side-effect of dump's caching. > > My top-of-head explanation is that each dump process has its own cache > but actual I/O is round-robined on a (roughly) block scale so a large > contiguous file will wind up in each 'slave' process's cache. > > The most obvious (and easiest) fixes are to either implement a shared > cache (though this means another level of inter-process communication) > or only use a single 'slave' process when caching is enabled. > > The cache algorithm could probably be enhanced as well - apart from > inode blocks, any block will only be accessed once so once a block has > been accessed, it can be purged from the cache (which is completely > opposite to a "normal" cache). > > -- > Peter Jeremy > Please excuse any delays as the result of my ISP's inability to implement > an MTA that is either RFC2821-compliant or matches their claimed behaviour. > _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[email protected]"
