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From: "Wang, Xiao W" <xiao.w.wang@intel.com>
To: Harman Kalra <hkalra@marvell.com>
CC: "Hunt, David" <david.hunt@intel.com>, "dev@dpdk.org" <dev@dpdk.org>,
"stable@dpdk.org" <stable@dpdk.org>
Thread-Topic: [dpdk-dev] [PATCH 2/2] l3fwd-power: fix interrupt disable
Thread-Index: AQHVz6QXCX+0gzBuR0qz3niTpkguUqf2KtEAgACUpHA=
Date: Wed, 22 Jan 2020 14:32:26 +0000
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References: <20200121030657.39048-1-xiao.w.wang@intel.com>
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Subject: Re: [dpdk-dev] [PATCH 2/2] l3fwd-power: fix interrupt disable
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Hi Kalra,
This patch is more about bug fix on user interrupt, no powering saving tuni=
ng.
The target scenario is, a worker core is dealing with 2 Rx queues, and it g=
o sleep due to no traffic for some time,
and then the first queue has new traffic arrived, and wakes up this core, s=
o this worker core is busy polling again.
The issue is that even though the core comes to polling state, the second q=
ueue will still send interrupt (if packet flushes in) to host.. This is wha=
t the core doesn't need, and unnecessary MSIX messages can cause throughput=
to degrade.
Best Regards,
Xiao
> -----Original Message-----
> From: Harman Kalra <hkalra@marvell.com>
> Sent: Wednesday, January 22, 2020 9:30 PM
> To: Wang, Xiao W <xiao.w.wang@intel.com>
> Cc: Hunt, David <david.hunt@intel.com>; dev@dpdk.org; stable@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH 2/2] l3fwd-power: fix interrupt disable
>=20
> On Mon, Jan 20, 2020 at 10:06:57PM -0500, Xiao Wang wrote:
> > Since all related queues' interrupts are turned on before epoll, we nee=
d
> > to turn off all the interrupts after wakeup. This patch fixes the issue
> > of only turning off the interrupted queues.
> >
> > Fixes: b736d64787fc ("examples/l3fwd-power: disable Rx interrupt when
> waking up")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
> > ---
> > examples/l3fwd-power/main.c | 13 +++++++------
> > 1 file changed, 7 insertions(+), 6 deletions(-)
> >
> > diff --git a/examples/l3fwd-power/main.c b/examples/l3fwd-power/main.c
> > index ffcc7ecf4..e9b2cb5b3 100644
> > --- a/examples/l3fwd-power/main.c
> > +++ b/examples/l3fwd-power/main.c
> > @@ -880,9 +880,6 @@ sleep_until_rx_interrupt(int num)
> > port_id =3D ((uintptr_t)data) >> CHAR_BIT;
> > queue_id =3D ((uintptr_t)data) &
> > RTE_LEN2MASK(CHAR_BIT, uint8_t);
> > - rte_spinlock_lock(&(locks[port_id]));
> > - rte_eth_dev_rx_intr_disable(port_id, queue_id);
> > - rte_spinlock_unlock(&(locks[port_id]));
> > RTE_LOG(INFO, L3FWD_POWER,
> > "lcore %u is waked up from rx interrupt on"
> > " port %d queue %d\n",
> > @@ -892,7 +889,7 @@ sleep_until_rx_interrupt(int num)
> > return 0;
> > }
> >
> > -static void turn_on_intr(struct lcore_conf *qconf)
> > +static void turn_on_off_intr(struct lcore_conf *qconf, bool on)
> > {
> > int i;
> > struct lcore_rx_queue *rx_queue;
> > @@ -905,7 +902,10 @@ static void turn_on_intr(struct lcore_conf *qconf)
> > queue_id =3D rx_queue->queue_id;
> >
> > rte_spinlock_lock(&(locks[port_id]));
> > - rte_eth_dev_rx_intr_enable(port_id, queue_id);
> > + if (on)
> > + rte_eth_dev_rx_intr_enable(port_id, queue_id);
> > + else
> > + rte_eth_dev_rx_intr_disable(port_id, queue_id);
>=20
> Hi Wang
>=20
> I tested this patch on octeontx2 platform and have some queries
> regarding the same:
> Difference what I observed with this patch is, you are disabling
> interrupts for all the queues handled by the core which woke up but
> what is the advantage of doing so?
> I dont see any difference wrt octeontx2, with and without this patch in
> term of power saving. Can you please explain what I am missing.
>=20
> Thanks
> Harman
>=20
> > rte_spinlock_unlock(&(locks[port_id]));
> > }
> > }
> > @@ -1340,9 +1340,10 @@ main_loop(__attribute__((unused)) void
> *dummy)
> > else {
> > /* suspend until rx interrupt triggers */
> > if (intr_en) {
> > - turn_on_intr(qconf);
> > + turn_on_off_intr(qconf, 1);
> > sleep_until_rx_interrupt(
> > qconf->n_rx_queue);
> > + turn_on_off_intr(qconf, 0);
> > /**
> > * start receiving packets immediately
> > */
> > --
> > 2.15.1
> >