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
