From: Neil Horman <nhorman@tuxdriver.com>
To: "Richardson, Bruce" <bruce.richardson@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 09:37:38 -0400 [thread overview]
Message-ID: <20141021133738.GC12795@hmsreliant.think-freely.org> (raw)
In-Reply-To: <59AF69C657FD0841A61C55336867B5B0344212BF@IRSMSX103.ger.corp.intel.com>
On Tue, Oct 21, 2014 at 10:43:03AM +0000, Richardson, Bruce wrote:
>
>
> > -----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.
>
But that presumes that no one has written the TSC via IA32_TIME_STAMP_COUNTER.
Assuming that something will never wrap just seems like bad practice here. We
should have a general purpose macro to handle wrapping counters like this, if
not for this case specficially, then in general.
Neil
> /Bruce
>
next prev parent reply other threads:[~2014-10-21 13:29 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
2014-10-21 13:37 ` Neil Horman [this message]
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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