[Jfs-discussion] Re: Desktop Filesystem Benchmarks in 2.6.3
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From: Hans R. <re...@na...> - 2004-03-03 09:31:01
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Unfortunately it is a bit more complex, and the truth is less complementary to us than what you write. Reiser4's CPU usage has come down a lot, but it still consumes more CPU than V3. It should consume less, and Zam is currently working on making writes more CPU efficient. As soon as I get funding from somewhere and can stop worrying about money, I will do a complete code review, and CPU usage will go way down. There are always lots of stupid little things that consume a lot of CPU that I find whenever I stop chasing money and review code. We are shipping because CPU usage is not as important as IO efficiency for a filesystem, and while Reiser4 is not as fast as it will be in 3-6 months, it is faster than anything else available so it should be shipped. Hans Dax Kelson wrote: >On Tue, 2004-03-02 at 09:34, Peter Nelson wrote: > > >>Hans Reiser wrote: >> >>I'm confused as to why performing a benchmark out of cache as opposed to >>on disk would hurt performance? >> >> > >My understanding (which could be completely wrong) is that reieserfs v3 >and v4 are algorithmically more complex than ext2 or ext3. Reiserfs >spends more CPU time to make the eventual ondisk operations more >efficient/faster. > >When operating purely or mostly out of ram, the higher CPU utilization >of reiserfs hurts performance compared to ext2 and ext3. > >When your system I/O utilization exceeds cache size and your disks >starting getting busy, the CPU time previously invested by reiserfs pays >big dividends and provides large performance gains versus more >simplistic filesystems. > >In other words, the CPU penalty paid by reiserfs v3/v4 is more than made >up for by the resultant more efficient disk operations. Reiserfs trades >CPU for disk performance. > >In a nutshell, if you have more memory than you know what do to with, >stick with ext3. If you spend all your time waiting for disk operations >to complete, go with reiserfs. > >Dax Kelson >Guru Labs > > > > > -- Hans |