Re: Read/Write NFS I/O performance degraded by FLUSH_STABLE page flushing

Trond Myklebust
2009-05-29T22:04:00Z

On Fri, 2009-05-29 at 17:55 -0400, Brian R Cowan wrote:
> So, it is possible that either pdflush is sending the commits or us, or
> that the commits are happening when the file closes, giving us one/tens of
> commits instead of hundreds or thousands. That's a big difference. The
> write RPCs still happen in RHEL 4, they just don't block the linker, or at
> least nowhere near as often. Since there is only one application/thread
> (the gcc linker) writing this file, the odds of another task getting
> stalled here are minimal at best.

No, you're not listening! That COMMIT is _synchronous_ and happens
before you can proceed with the READ request. There is no economy of
scale as you seem to assume.

Trond