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From: Stephen Hemminger <stephen@networkplumber.org>
To: Bruce Richardson <bruce.richardson@intel.com>
Cc: Jim Harris <james.r.harris@intel.com>,
	dev@dpdk.org, anatoly.burakov@intel.com
Subject: Re: [dpdk-dev] [PATCH v2 RESEND] timer: remove check_tsc_flags()
Date: Tue, 8 Oct 2019 08:15:47 -0700	[thread overview]
Message-ID: <20191008081547.2b002519@hermes.lan> (raw)
In-Reply-To: <20191008083649.GA1856@bricha3-MOBL.ger.corp.intel.com>

On Tue, 8 Oct 2019 09:36:49 +0100
Bruce Richardson <bruce.richardson@intel.com> wrote:

> On Mon, Oct 07, 2019 at 04:18:54PM -0700, Stephen Hemminger wrote:
> > On Mon, 07 Oct 2019 08:40:05 -0700 Jim Harris <james.r.harris@intel.com>
> > wrote:
> >   
> > > This code was added 7+ years ago:
> > > 
> > > commit fb022b85bae4 ("timer: check TSC reliability")
> > > 
> > > presumably when variant TSCs were still somewhat common?  But this code
> > > doesn't do anything except print a warning, and the warning doesn't
> > > give any kind of advice to the user, so let's just remove it.
> > > 
> > > While the warning has no functional meaning, the /proc/cpuinfo parsing
> > > consumes a non-trivial amount of time which is especially noticeable in
> > > secondary processes.  On my test system, it consumes 21ms out of the
> > > 66ms total execution time for rte_eal_init() in a secondary process.
> > > 
> > > Signed-off-by: Jim Harris <james.r.harris@intel.com>  
> > 
> > Yes this code is dead.
> > 
> > Acked-by: Stephen Hemminger <stephen@networkplumber.org>
> >   
> 
> +1 for this. Even if it was needed, we should never parse /proc/cpuinfo,
> since we have a DPDK function to query cpuid directly anyway.
> 
> Acked-by: Bruce Richardson <bruce.richardson@intel.com>

It also turns out that Hyper-V/Azure report unstable TSC because
when VM is migrated there are blips in TSC. There upcoming changes to
handle that in Hypervisor and Linux drivers.

  reply	other threads:[~2019-10-08 15:15 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-21 10:18 [dpdk-dev] [PATCH v2] " Jim Harris
2019-10-07 15:40 ` [dpdk-dev] [PATCH v2 RESEND] " Jim Harris
2019-10-07 23:18   ` Stephen Hemminger
2019-10-08  8:36     ` Bruce Richardson
2019-10-08 15:15       ` Stephen Hemminger [this message]
2019-10-18  4:10         ` David Marchand

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