Re: [PATCH 0/3] Ext3 latency improvement patches

Jeff Garzik
2009-03-28T00:14:42Z

Theodore Tso wrote:
> OTOH, the really big databases will tend to use direct I/O, so they
> won't be dirtying the page cache anyway. So maybe it's not worth the

Not necessarily... From what I understand, a lot of the individual
low-level components in cloud storage, such as GoogleFS's chunk
server[1] do not bypass the page cache, even though they do care about
the details of data caching and data consistency.

I am looking at the same areas for my own distributed storage work, and
am finding that the current crop of Linux-specific,
database/server-friendly syscalls permit more application control over
pagecache usage than in past years, decreasing the need for O_DIRECT.
Things like readahead(2), sync_file_range(2), fadvise(3), really help.

Jeff

[1] http://labs.google.com/papers/gfs-sosp2003.pdf