Re: [PATCH 00/23] per device dirty throttling -v8

Andi Kleen
2007-08-05T00:26:53Z

Ingo Molnar <mingo@elte.hu> writes:
>
> yeah, it's really ugly. But otherwise i've got no real complaint about
> ext3 - with the obligatory qualification that "noatime,nodiratime" in
> /etc/fstab is a must. This speeds up things very visibly - especially
> when lots of files are accessed. It's kind of weird that every Linux
> desktop and server is hurt by a noticeable IO performance slowdown due
> to the constant atime updates, while there's just two real users of it:
> tmpwatch [which can be configured to use ctime so it's not a big issue]
> and some backup tools. (Ok, and mail-notify too i guess.) Out of tens of
> thousands of applications. So for most file workloads we give Windows a
> 20%-30% performance edge, for almost nothing. (for RAM-starved kernel
> builds the performance difference between atime and noatime+nodiratime
> setups is more on the order of 40%)

I always thought the right solution would be to just sync atime only
very very lazily. This means if a inode is only dirty because of an
atime update put it on a "only write out when there is nothing to do
or the memory is really needed" list.

-Andi