[sheepdog] [PATCH] sheep: check resource limit at startup

[MORITA Kazutaka]

At Tue, 29 Jan 2013 13:13:47 +0900,
MORITA Kazutaka wrote:
> > 
> > 
> > > BTW, Is it difficult to modify sheepdog so that it doesn't use so many
> > > FDs?
> > > 
> > 
> > I think yes. Currently the biggest user of FD is sockfd cache and
> > pusher's push threads, which is performance critical. If we limit the FD
> > to some ceiling, then I guess we'll lose the performance.
> 
> Exceeding the RLIM_NOFILE value leads to EIO of VMs, doesn't it?  If
> yes, it should be definitely avoided.  Is limiting the number of
> consuming sockfds according to the current RLIM_NOFILE also difficult?
> If we can do it, setting a large value to RLIM_NOFILE doesn't affect
> the sheepdog performance.

Another option is to handle the EMFILE error gracefully (e.g. retrying
after some file descriptors are closed) so that VMs aren't aware of
sheepdog internal error.

Thanks,

Kazutaka