This is a good point, and something that I tried. I limited the ARC to 1GB and 4GB (both well within the memory footprint of the system even with the ramdisk).....equally poor results....this doesn't feel like ARC righting with locked memory pages.
--M -----Original Message----- From: Ross Walker [mailto:rswwal...@gmail.com] Sent: Tuesday, March 09, 2010 3:53 PM To: Roch Bourbonnais Cc: Matt Cowger; zfs-discuss@opensolaris.org Subject: Re: [zfs-discuss] terrible ZFS performance compared to UFS on ramdisk (70% drop) On Mar 9, 2010, at 1:42 PM, Roch Bourbonnais <roch.bourbonn...@sun.com> wrote: > > I think This is highlighting that there is extra CPU requirement to > manage small blocks in ZFS. > The table would probably turn over if you go to 16K zfs records and > 16K reads/writes form the application. > > Next step for you is to figure how much reads/writes IOPS do you > expect to take in the real workloads and whether or not the > filesystem portion > will represent a significant drain of CPU resource. I think it highlights more the problem of ARC vs ramdisk, or specifically ZFS on ramdisk while ARC is fighting with ramdisk for memory. It is a wonder it didn't deadlock. If I were to put a ZFS file system on a ramdisk, I would limit the size of the ramdisk and ARC so both, plus the kernel fit nicely in memory with room to spare for user apps. -Ross _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
