Re: high load, no bottleneck

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Sat, Sep 28, 2013 at 06:25:22AM +0200, Emmanuel Dreyfus wrote:
> 
> Basically, if we have N pending VOP_FSYNC for a given filesystem, all
> theses requests will be honoured on first flush, but they are serialized
> and will be acknowledged one by one, with the cost of a useless flush
> each time. Am I right?

Do you mean "all these requests *could* be honored on first flush"?  If
so, then yes, I agree.

Unfortunately, it may be that we lost some of the framework necessary to
do this when we reverted the softdep code.  Looking at the code in XFS
that gathers barrier events, it seems to be drawing a DAG...