From: Jerin Jacob <jerin.jacob@caviumnetworks.com>
To: Olivier Matz <olivier.matz@6wind.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] mbuf: reduce pktmbuf init cycles
Date: Fri, 23 Jun 2017 15:36:44 +0530 [thread overview]
Message-ID: <20170623100642.GA25523@jerin> (raw)
In-Reply-To: <20170623114230.54dadacd@platinum>
-----Original Message-----
> Date: Fri, 23 Jun 2017 11:42:30 +0200
> From: Olivier Matz <olivier.matz@6wind.com>
> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] mbuf: reduce pktmbuf init cycles
> X-Mailer: Claws Mail 3.14.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu)
>
> On Mon, 5 Jun 2017 22:08:07 +0530, Jerin Jacob <jerin.jacob@caviumnetworks.com> wrote:
> > There is no need for initializing the complete
> > packet buffer with zero as the packet data area will be
> > overwritten by the NIC Rx HW anyway.
> >
> > The testpmd configures the packet mempool
> > with around 180k buffers with
> > 2176B size. In existing scheme, the init routine
> > needs to memset around ~370MB vs the proposed scheme
> > requires only around ~44MB on 128B cache aligned system.
> >
> > Useful in running DPDK in HW simulators/emulators,
> > where millions of cycles have an impact on boot time.
> >
> > Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> > ---
> > lib/librte_mbuf/rte_mbuf.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
> > index 0e3e36a58..1d5ce7816 100644
> > --- a/lib/librte_mbuf/rte_mbuf.c
> > +++ b/lib/librte_mbuf/rte_mbuf.c
> > @@ -131,8 +131,7 @@ rte_pktmbuf_init(struct rte_mempool *mp,
> > RTE_ASSERT(mp->elt_size >= mbuf_size);
> > RTE_ASSERT(buf_len <= UINT16_MAX);
> >
> > - memset(m, 0, mp->elt_size);
> > -
> > + memset(m, 0, mbuf_size + RTE_PKTMBUF_HEADROOM);
> > /* start of buffer is after mbuf structure and priv data */
> > m->priv_size = priv_size;
> > m->buf_addr = (char *)m + mbuf_size;
>
> Yes, I don't foresee any risk to do that.
>
> I'm just wondering why RTE_PKTMBUF_HEADROOM should be zeroed.
> For example, rte_pktmbuf_free() does not touch the data either, so
> after some packets processing, we also have garbage data in the
> headroom.
Yes. Headroom can be garbage as application pull the packet offset up and writes
new header on encapsulation use case.
I will the send v2 with clearing only mbuf area.
>
> Olivier
next prev parent reply other threads:[~2017-06-23 10:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-05 16:38 Jerin Jacob
2017-06-23 9:42 ` Olivier Matz
2017-06-23 10:06 ` Jerin Jacob [this message]
2017-06-27 11:57 ` [dpdk-dev] [PATCH v2] " Jerin Jacob
2017-06-30 12:27 ` Olivier Matz
2017-07-01 10:15 ` Thomas Monjalon
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