lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Thu, 03 Jan 2013 10:32:49 -0500
From:	Steven Rostedt <>
To:	Eric Dumazet <>
Cc:	Jan Beulich <>, Rik van Riel <>,,,,,,,
Subject: Re: [RFC PATCH 3/3 -v2] x86,smp: auto tune spinlock backoff delay

On Thu, 2013-01-03 at 05:35 -0800, Eric Dumazet wrote:
> On Thu, 2013-01-03 at 08:24 -0500, Steven Rostedt wrote:
> > On Thu, 2013-01-03 at 09:05 +0000, Jan Beulich wrote:
> > 
> > > > How much bus traffic do monitor/mwait cause behind the scenes?
> > > 
> > > I would suppose that this just snoops the bus for writes, but the
> > > amount of bus traffic involved in this isn't explicitly documented.
> > > 
> > > One downside of course is that unless a spin lock is made occupy
> > > exactly a cache line, false wakeups are possible.
> > 
> > And that would probably be very likely, as the whole purpose of Rik's
> > patches was to lower cache stalls due to other CPUs pounding on spin
> > locks that share the cache line of what is being protected (and
> > modified).
> A monitor/mwait would be an option only if using MCS (or K42 variant)
> locks, where each cpu would wait on a private and dedicated cache line.

But then would the problem even exist? If the lock is on its own cache
line, it shouldn't cause a performance issue if other CPUs are spinning
on it. Would it?

-- Steve

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists