diff mbox series

[v2,RESEND] timer: remove check_tsc_flags()

Message ID 157046280565.10885.5236700707414855268.stgit@jrharri1-skx (mailing list archive)
State Accepted, archived
Delegated to: David Marchand
Headers
Series [v2,RESEND] timer: remove check_tsc_flags() |

Checks

Context Check Description
ci/checkpatch success coding style OK
ci/iol-compilation success Compile Testing PASS
ci/iol-intel-Performance success Performance Testing PASS
ci/Intel-compilation success Compilation OK
ci/iol-mellanox-Performance success Performance Testing PASS

Commit Message

Harris, James R Oct. 7, 2019, 3:40 p.m. UTC 
  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>
---
 lib/librte_eal/linux/eal/eal_timer.c |   36 ----------------------------------
 1 file changed, 36 deletions(-)

Comments

Stephen Hemminger Oct. 7, 2019, 11:18 p.m. UTC | #1 
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>
Bruce Richardson Oct. 8, 2019, 8:36 a.m. UTC | #2 
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>
Stephen Hemminger Oct. 8, 2019, 3:15 p.m. UTC | #3 
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.
David Marchand Oct. 18, 2019, 4:10 a.m. UTC | #4 
On Tue, Oct 8, 2019 at 5:16 PM Stephen Hemminger
<stephen@networkplumber.org> wrote:
>
> 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>
> > > Acked-by: Stephen Hemminger <stephen@networkplumber.org>
> > Acked-by: Bruce Richardson <bruce.richardson@intel.com>

Applied, thanks.


--
David Marchand
diff mbox series

Patch

diff --git a/lib/librte_eal/linux/eal/eal_timer.c b/lib/librte_eal/linux/eal/eal_timer.c
index 76ec17034..a904a8297 100644
--- a/lib/librte_eal/linux/eal/eal_timer.c
+++ b/lib/librte_eal/linux/eal/eal_timer.c
@@ -192,41 +192,6 @@  rte_eal_hpet_init(int make_default)
 }
 #endif
 
-static void
-check_tsc_flags(void)
-{
-	char line[512];
-	FILE *stream;
-
-	stream = fopen("/proc/cpuinfo", "r");
-	if (!stream) {
-		RTE_LOG(WARNING, EAL, "WARNING: Unable to open /proc/cpuinfo\n");
-		return;
-	}
-
-	while (fgets(line, sizeof line, stream)) {
-		char *constant_tsc;
-		char *nonstop_tsc;
-
-		if (strncmp(line, "flags", 5) != 0)
-			continue;
-
-		constant_tsc = strstr(line, "constant_tsc");
-		nonstop_tsc = strstr(line, "nonstop_tsc");
-		if (!constant_tsc || !nonstop_tsc)
-			RTE_LOG(WARNING, EAL,
-				"WARNING: cpu flags "
-				"constant_tsc=%s "
-				"nonstop_tsc=%s "
-				"-> using unreliable clock cycles !\n",
-				constant_tsc ? "yes":"no",
-				nonstop_tsc ? "yes":"no");
-		break;
-	}
-
-	fclose(stream);
-}
-
 uint64_t
 get_tsc_freq(void)
 {
@@ -263,6 +228,5 @@  rte_eal_timer_init(void)
 	eal_timer_source = EAL_TIMER_TSC;
 
 	set_tsc_freq();
-	check_tsc_flags();
 	return 0;
 }