smbd: High CPU usage

[Volker Lendecke]

On Wed, Jul 18, 2018 at 04:16:46PM -0700, Jeremy Allison via samba-technical wrote:
> On Wed, Jul 18, 2018 at 09:20:10PM +0300, Vadim Lazovskiy via samba-technical wrote:
> > I would not agree.
> > sendfile is great. It makes you able to serve content directly from disk to
> > network without unnessesery copying to userspace. It saves you lots
> > syscalls and context switching.
> > As for our workload profile (1-2Gbit per server) it really saves CPU time.
> > 
> > If someone of samba developers treat this as bug and eager to fix it I
> > could provide extra information and do some debugging.
> 
> Here is a full patchset that should handle all platforms
> for which we support sendfile(). Can you try it out and confirm it
> fixes your issue ?

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.

Volker

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