From: Thomas Gleixner <tglx@linutronix.de>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Christoph Lameter <cl@linux.com>,
Richard Cochran <richardcochran@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: Why do we still have 32 bit counters? Interrupt counters overflow within 50 days
Date: Mon, 6 Oct 2014 09:54:14 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.11.1410060952030.4383@nanos> (raw)
In-Reply-To: <1412553572.11091.29.camel@edumazet-glaptop2.roam.corp.google.com>
On Sun, 5 Oct 2014, Eric Dumazet wrote:
> On Sun, 2014-10-05 at 23:49 +0200, Thomas Gleixner wrote:
>
> > Whats so hard about 64bit counters on 32bit machines?
>
> Not hard, but not trivial either.
>
> >
> > > expensive to handle in particular because these counters are used in
> > > performance critical hotpaths.
> >
> > The expensive overhead is a single "adcl" instruction.
> >
>
> Assuming a reader do not care of reading garbage yes, while carry is not
> yet propagated.
Readers and writers are serialized via desc->lock.
Thanks,
tglx
next prev parent reply other threads:[~2014-10-06 7:54 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-03 9:45 Why do we still have 32 bit counters? Interrupt counters overflow within 50 days Christoph Lameter
2014-10-03 10:33 ` Thomas Gleixner
2014-10-03 11:54 ` Christoph Lameter
2014-10-03 12:03 ` Richard Cochran
2014-10-03 12:07 ` Christoph Lameter
2014-10-03 12:17 ` Richard Cochran
2014-10-03 14:04 ` Christoph Lameter
2014-10-05 21:49 ` Thomas Gleixner
2014-10-05 23:24 ` Christoph Lameter
2014-10-05 23:57 ` Eric Dumazet
2014-10-06 8:06 ` Thomas Gleixner
2014-10-06 10:22 ` Christoph Lameter
2014-10-06 13:01 ` Thomas Gleixner
2014-10-06 15:16 ` Christoph Lameter
2014-10-06 15:28 ` Thomas Gleixner
2014-10-06 19:34 ` Henrique de Moraes Holschuh
2014-10-06 15:31 ` David Lang
2014-10-06 19:45 ` Christoph Lameter
2014-10-05 23:59 ` Eric Dumazet
2014-10-06 7:54 ` Thomas Gleixner [this message]
2014-10-06 10:49 ` David Lang
2014-10-06 12:28 ` Thomas Gleixner
2014-10-03 12:15 ` Paul Bolle
2014-10-03 12:23 ` Christoph Lameter
2014-10-04 10:26 ` Bernd Petrovitsch
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