smbd: High CPU usage

[Jeremy Allison]

On Thu, Jul 19, 2018 at 06:34:35PM +0200, Volker Lendecke wrote:
> On Thu, Jul 19, 2018 at 09:02:30AM -0700, Jeremy Allison via samba-technical wrote:
> > > I know syscalls are cheap, but don't the additional fcntl ones kill
> > > the performance advantage somewhat? We had discussions with a
> > > MIPS-based vendor in the past. On that platform (don't remember the
> > > exact OS version), syscalls were pretty expensive.
> > 
> > If you want performance, use a pthreadpool :-).
> 
> Not sure in the MIPS case. This adds even more syscalls and context
> switches. For better performance, we should look at preadv2 with
> RWF_NOWAIT to avoid the context switch for buffered reads.

Yeah, I'm just moaning :-). I have an updated patchset
which switches to blocking only on EAGAIN/EWOULDBLOCK.

I'll post shortly.

Jeremy.