Re: Link performance over NFS degraded in RHEL5. -- was : Read/Write NFS I/O performance degraded by FLUSH_STABLE page flushing

Trond Myklebust
2009-06-04T20:57:26Z

On Thu, 2009-06-04 at 16:43 -0400, Brian R Cowan wrote:
> What I'm trying to understand is why RHEL 4 is not flushing anywhere near
> as often. Either RHEL4 erred on the side of not writing, and RHEL5 is
> erring on the opposite side, or RHEL5 is doing unnecessary flushes... I've
> seen that 2.6.29 flushes less than the Red hat 2.6.18-derived kernels, but
> it still flushes a lot more than RHEL 4 does.

Most of that increase is probably mainly due to the changes to the way
stat() works. More precisely, it would be due to this patch:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git&a=commitdiff&h=70b9ecbdb9c5fdc731f8780bffd45d9519020c4a

which went into Linux 2.6.16 in order to fix a posix compatibility
issue.

Trond