From: Harish Patil <harish.patil@qlogic.com>
To: Bruce Richardson <bruce.richardson@intel.com>,
"Charles (Chas) Williams" <3chas3@gmail.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] bnx2x: set Ethernet address type during transmit for VF's
Date: Tue, 8 Dec 2015 21:48:52 +0000 [thread overview]
Message-ID: <D28C8E3C.109BE7%harish.patil@qlogic.com> (raw)
In-Reply-To: <20151208213830.GA24204@bricha3-MOBL3>
>On Tue, Dec 08, 2015 at 09:27:05AM -0500, Charles (Chas) Williams wrote:
>> On Mon, 2015-12-07 at 17:29 +0000, Harish Patil wrote:
>> > >
>> > >On Sun, 2015-12-06 at 23:34 +0000, Harish Patil wrote:
>> > >> >
>> > >> >The original was always setting unicast. While here, clean up
>>some
>> > >> >other references that also point into the Ethernet header.
>> > >> >
>> > >> >Signed-off-by: Chas Williams <3chas3@gmail.com>
>> > >> >---
>> > >> > drivers/net/bnx2x/bnx2x.c | 23 +++++++++++++++--------
>> > >> > drivers/net/bnx2x/ecore_hsi.h | 5 +++--
>> > >> > 2 files changed, 18 insertions(+), 10 deletions(-)
>> > >> >
>> > >> >diff --git a/drivers/net/bnx2x/bnx2x.c b/drivers/net/bnx2x/bnx2x.c
>> > >> >index 76444eb..294711f 100644
>> > >> >--- a/drivers/net/bnx2x/bnx2x.c
>> > >> >+++ b/drivers/net/bnx2x/bnx2x.c
>> > >> >@@ -2177,25 +2177,32 @@ int bnx2x_tx_encap(struct bnx2x_tx_queue
>>*txq,
>> > >> >struct rte_mbuf **m_head, int m_p
>> > >> > bd_prod = NEXT_TX_BD(bd_prod);
>> > >> > if (IS_VF(sc)) {
>> > >> > struct eth_tx_parse_bd_e2 *tx_parse_bd;
>> > >> >- uint8_t *data = rte_pktmbuf_mtod(m0,
>>uint8_t *);
>> > >> >+ const struct ether_hdr *eh =
>> > >>rte_pktmbuf_mtod(m0, struct ether_hdr *);
>> > >> >+ uint8_t mac_type = UNICAST_ADDRESS;
>> > >> >
>> > >> > tx_parse_bd =
>> > >> > &txq->tx_ring[TX_BD(bd_prod,
>> > >>txq)].parse_bd_e2;
>> > >> >+ if (is_multicast_ether_addr(&eh->d_addr)) {
>> > >>
>> > >> Minor comment. unlikely() may be used here to keep it consistent
>>with
>> > >>base
>> > >> driver.
>> > >
>> > >It wasn't clear to me that this code path is all that unlikely().
>> >
>> > Its an optional comment, unlikely() is because fast path traffic is
>>mostly
>> > unicast.
>>
>> Multicast traffic isn't all that uncommon. I also don't see that we
>>gain
>> much from branch prediction here regardless. My understanding is that
>> unlikely() should be used for really unlikely situations since the
>>branch
>> will not be optimized.
>
>+1 to this.
>
>Let the cpu branch predictor do the work at run-time picking the
>correct leg of the branch. likely()/unlikely() should only ever be used
>for
>things like fatal error conditions where it doesn't matter how optimized
>the
>unlikely branch part is. For normal code where there is no error, don't
>try and
>optimize it using likely()/unlikely() unless you can prove there is a
>definite
>performance improvement by doing so.
>
>/Bruce
>
I agree too, lets leave it that way. As I said its optional, to be same as
linux base driver which has:
3809 /* set flag according to packet type (UNICAST_ADDRESS is
default)*/
3810 if (unlikely(is_multicast_ether_addr(eth->h_dest))) {
Thanks,
Harish
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prev parent reply other threads:[~2015-12-08 21:48 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-18 20:58 Chas Williams
2015-12-06 22:20 ` Thomas Monjalon
2015-12-06 22:22 ` Thomas Monjalon
2015-12-06 23:34 ` Harish Patil
2015-12-07 11:01 ` Charles (Chas) Williams
2015-12-07 17:29 ` Harish Patil
2015-12-08 14:27 ` Charles (Chas) Williams
2015-12-08 21:38 ` Bruce Richardson
2015-12-08 21:48 ` Harish Patil [this message]
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