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From: "Richardson, Bruce" <bruce.richardson@intel.com>
To: Neil Horman <nhorman@tuxdriver.com>,
	"Liang, Cunming" <cunming.liang@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v2 1/4] app/test: unit test for rx and tx cycles/packet
Date: Tue, 21 Oct 2014 10:43:03 +0000	[thread overview]
Message-ID: <59AF69C657FD0841A61C55336867B5B0344212BF@IRSMSX103.ger.corp.intel.com> (raw)
In-Reply-To: <20141021103315.GB12795@hmsreliant.think-freely.org>



> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Neil Horman
> Sent: Tuesday, October 21, 2014 11:33 AM
> To: Liang, Cunming
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v2 1/4] app/test: unit test for rx and tx
> cycles/packet
> 
> > >
> > > > +	if (count == 0)
> > > > +		return -1;
> > > > +
> > > > +	printf("%lu packet, %lu drop, %lu idle\n", count, drop, idle);
> > > > +	printf("Result: %ld cycles per packet\n", (cur_tsc - prev_tsc) / count);
> > > > +
> > > Bad math here.  Theres no guarantee that the tsc hasn't wrapped (potentially
> > > more than once) depending on your test length.  you need to check the tsc
> before
> > > and after each burst and record an average of deltas instead, accounting in
> each
> > > instance for the possibility of wrap.
> > [Liang, Cunming] I'm not sure catch your point correctly.
> > I think both cur_tsc and prev_tsc are 64 bits width.
> > For 3GHz, I think it won't wrapped so quick.
> > As it's uint64_t, so even get wrapped, the delta should still be correct.
> But theres no guarantee that the tsc starts at zero when you begin your test.
> The system may have been up for a long time and near wrapping already.
> Regardless, you need to account for the possibility that cur_tsc is smaller
> than prev_tsc, or this breaks.
> 

The tsc. is 64-bit and so only wraps around every couple of hundred years or so on a 2GHz machine, so I don't think it's necessary to handle that case. 

/Bruce

  reply	other threads:[~2014-10-21 10:34 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-25  6:12 [dpdk-dev] [PATCH 0/5] app/test: unit test to measure cycles per packet Cunming Liang
2014-08-25  6:12 ` [dpdk-dev] [PATCH 1/5] app/test: unit test for rx and tx cycles/packet Cunming Liang
2014-08-25  6:12 ` [dpdk-dev] [PATCH 2/5] app/test: measure standalone rx or " Cunming Liang
2014-08-25  6:12 ` [dpdk-dev] [PATCH 3/5] ixgbe/vpmd: add fix to store unaligned mbuf point array Cunming Liang
2014-08-25  6:12 ` [dpdk-dev] [PATCH 4/5] app/test: add unit test to measure RX burst cycles Cunming Liang
2014-08-25  6:12 ` [dpdk-dev] [PATCH 5/5] app/test: allow to create packets in different sizes Cunming Liang
2014-09-03  1:46 ` [dpdk-dev] [PATCH 0/5] app/test: unit test to measure cycles per packet Zhan, Zhaochen
2014-10-10 12:29 ` [dpdk-dev] [PATCH v2 0/4] " Cunming Liang
2014-10-10 12:29   ` [dpdk-dev] [PATCH v2 1/4] app/test: unit test for rx and tx cycles/packet Cunming Liang
2014-10-10 17:52     ` Neil Horman
2014-10-12 11:10       ` Liang, Cunming
     [not found]         ` <E115CCD9D858EF4F90C690B0DCB4D8972262B720@IRSMSX108.ger.corp.intel.com>
2014-10-14  0:54           ` Liang, Cunming
2014-10-21 10:33         ` Neil Horman
2014-10-21 10:43           ` Richardson, Bruce [this message]
2014-10-21 13:37             ` Neil Horman
2014-10-21 22:43               ` Ananyev, Konstantin
2014-10-21 13:17           ` Liang, Cunming
2014-10-22 14:03             ` Neil Horman
2014-10-22 14:48               ` Liang, Cunming
2014-10-22 14:53               ` Ananyev, Konstantin
2014-10-22 15:09                 ` Richardson, Bruce
2014-10-24  3:06                   ` Liang, Cunming
2014-10-10 12:29   ` [dpdk-dev] [PATCH v2 2/4] app/test: measure standalone rx or " Cunming Liang
2014-10-10 12:30   ` [dpdk-dev] [PATCH v2 3/4] app/test: add unit test to measure RX burst cycles Cunming Liang
2014-10-10 12:30   ` [dpdk-dev] [PATCH v2 4/4] app/test: allow to create packets in different sizes Cunming Liang
2014-10-20  8:13   ` [dpdk-dev] [PATCH v3 0/2] app/test: unit test to measure cycles per packet Cunming Liang
2014-10-20  8:13     ` [dpdk-dev] [PATCH v3 1/2] app/test: allow to create packets in different sizes Cunming Liang
2014-10-20  8:13     ` [dpdk-dev] [PATCH v3 2/2] app/test: measure the cost of rx/tx routines by cycle number Cunming Liang
2014-10-21  2:40     ` [dpdk-dev] [PATCH v3 0/2] app/test: unit test to measure cycles per packet Liu, Yong
2014-10-24  5:39     ` [dpdk-dev] [PATCH v4 0/3] " Cunming Liang
2014-10-24  5:39       ` [dpdk-dev] [PATCH v4 1/3] app/test: allow to create packets in different sizes Cunming Liang
2014-10-24  5:39       ` [dpdk-dev] [PATCH v4 2/3] app/test: measure the cost of rx/tx routines by cycle number Cunming Liang
2014-10-24  5:39       ` [dpdk-dev] [PATCH v4 3/3] ethdev: fix wrong error return refer to API definition Cunming Liang
2014-10-24  5:57       ` [dpdk-dev] [PATCH v5 0/3] app/test: unit test to measure cycles per packet Cunming Liang
2014-10-24  5:58         ` [dpdk-dev] [PATCH v5 1/3] app/test: allow to create packets in different sizes Cunming Liang
2014-10-24  5:58         ` [dpdk-dev] [PATCH v5 2/3] app/test: measure the cost of rx/tx routines by cycle number Cunming Liang
2014-10-24  5:58         ` [dpdk-dev] [PATCH v5 3/3] ethdev: fix wrong error return refere to API definition Cunming Liang
2014-10-27  1:20         ` [dpdk-dev] [PATCH v6 0/3] app/test: unit test to measure cycles per packet Cunming Liang
2014-10-27  1:20           ` [dpdk-dev] [PATCH v6 1/3] app/test: allow to create packets in different sizes Cunming Liang
2014-10-27  1:20           ` [dpdk-dev] [PATCH v6 2/3] app/test: measure the cost of rx/tx routines by cycle number Cunming Liang
2014-11-11 23:28             ` Thomas Monjalon
2014-11-12  6:32               ` Liang, Cunming
2014-10-27  1:20           ` [dpdk-dev] [PATCH v6 3/3] ethdev: fix wrong error return refere to API definition Cunming Liang
2014-10-27 16:03             ` Ananyev, Konstantin
2014-10-27  1:45           ` [dpdk-dev] [PATCH v6 0/3] app/test: unit test to measure cycles per packet Liu, Yong
2014-10-29  5:06           ` Liang, Cunming
2014-11-12  6:24           ` [dpdk-dev] [PATCH v7 0/7] " Cunming Liang
2014-11-12  6:24             ` [dpdk-dev] [PATCH v7 1/7] app/test: allow to create packets in different sizes Cunming Liang
2014-11-12  6:24             ` [dpdk-dev] [PATCH v7 2/7] ixgbe:clean scattered_rx configure in dev_stop Cunming Liang
2014-11-12  7:53               ` Thomas Monjalon
2014-11-12  8:21                 ` Liang, Cunming
2014-11-12  9:24                   ` Thomas Monjalon
2014-11-12 10:29                     ` Liang, Cunming
2014-11-12 10:32                       ` Thomas Monjalon
2014-11-12 10:42                         ` Liang, Cunming
2014-11-12  6:24             ` [dpdk-dev] [PATCH v7 3/7] ether: new API to format eth_addr in string Cunming Liang
2014-11-12  6:24             ` [dpdk-dev] [PATCH v7 4/7] app/testpmd: cleanup eth_addr print Cunming Liang
2014-11-12  6:24             ` [dpdk-dev] [PATCH v7 5/7] examples: " Cunming Liang
2014-11-12  6:24             ` [dpdk-dev] [PATCH v7 6/7] app/test: measure the cost of rx/tx routines by cycle number Cunming Liang
2014-11-12  6:24             ` [dpdk-dev] [PATCH v7 7/7] ethdev: fix wrong error return refere to API definition Cunming Liang
2014-11-12 23:50             ` [dpdk-dev] [PATCH v7 0/7] app/test: unit test to measure cycles per packet Thomas Monjalon
2014-10-24  5:59       ` [dpdk-dev] [PATCH v4 0/3] " Liang, Cunming
     [not found]       ` <1414130090-17910-1-git-send-email-y>
     [not found]         ` <1414130090-17910-4-git-send-email-y>
2014-10-24 11:04           ` [dpdk-dev] [PATCH v5 3/3] ethdev: fix wrong error return refere to API definition Ananyev, Konstantin
2014-10-27  0:58             ` Liang, Cunming
2014-10-28 12:21   ` [dpdk-dev] [PATCH v2 0/4] app/test: unit test to measure cycles per packet Neil Horman

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