From: "Mattias Rönnblom" <mattias.ronnblom@ericsson.com>
To: Stephen Hemminger <stephen@networkplumber.org>, dev@dpdk.org
Subject: Re: [dpdk-dev] [RFC 4/4] net/ether: use bitops to speedup comparison
Date: Thu, 16 May 2019 11:03:10 +0200 [thread overview]
Message-ID: <95e9a56f-5d33-2a53-033d-d8963193cbea@ericsson.com> (raw)
In-Reply-To: <20190515221952.21959-5-stephen@networkplumber.org>
On 2019-05-16 00:19, Stephen Hemminger wrote:
> Using bit operations like or and xor is faster than a loop
> on all architectures. Really just explicit unrolling.
>
> Similar cast to uint16 unaligned is already done in
> other functions here.
>
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
> lib/librte_net/rte_ether.h | 17 +++++++----------
> 1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h
> index b94e64b2195e..5d9242cda230 100644
> --- a/lib/librte_net/rte_ether.h
> +++ b/lib/librte_net/rte_ether.h
> @@ -78,11 +78,10 @@ struct ether_addr {
> static inline int is_same_ether_addr(const struct ether_addr *ea1,
> const struct ether_addr *ea2)
> {
> - int i;
> - for (i = 0; i < ETHER_ADDR_LEN; i++)
> - if (ea1->addr_bytes[i] != ea2->addr_bytes[i])
> - return 0;
> - return 1;
> + const unaligned_uint16_t *w1 = (const uint16_t *)ea1;
> + const unaligned_uint16_t *w2 = (const uint16_t *)ea2;
> +
> + return ((w1[0] ^ w2[0]) | (w1[1] ^ w2[1]) | (w1[2] ^ w2[2])) == 0;
> }
>
If you want to shave off a couple of instructions, you can switch the
three 16-bit loads to one 32-bit and one 16-bit load.
Something like:
const uint8_t *ea1_b = (const uint8_t *)ea1;
const uint8_t *ea2_b = (const uint8_t *)ea2;
uint32_t ea1_h;
uint32_t ea2_h;
uint16_t ea1_l;
uint16_t ea2_l;
memcpy(&ea1_h, &ea1_b[0], sizeof(ea1_h));
memcpy(&ea1_l, &ea1_b[sizeof(ea1_h)], sizeof(ea1_l));
memcpy(&ea2_h, &ea2_b[0], sizeof(ea2_h));
memcpy(&ea2_l, &ea2_b[sizeof(ea2_h)], sizeof(ea2_l));
return ((ea1_l ^ ea2_l) | (ea1_h ^ ea2_h)) == 0;
Code is not as clean as your solution though.
> /**
> @@ -97,11 +96,9 @@ static inline int is_same_ether_addr(const struct ether_addr *ea1,
> */
> static inline int is_zero_ether_addr(const struct ether_addr *ea)
> {
> - int i;
> - for (i = 0; i < ETHER_ADDR_LEN; i++)
> - if (ea->addr_bytes[i] != 0x00)
> - return 0;
> - return 1;
> + const unaligned_uint16_t *w = (const uint16_t *)ea;
> +
> + return (w[0] | w[1] | w[2]) == 0;
> }
>
> /**
>
next prev parent reply other threads:[~2019-05-16 9:03 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-15 22:19 [dpdk-dev] [RFC 0/4] net/ether: improvements Stephen Hemminger
2019-05-15 22:19 ` Stephen Hemminger
2019-05-15 22:19 ` [dpdk-dev] [RFC 1/4] net/ether: deinline non-critical functions Stephen Hemminger
2019-05-15 22:19 ` Stephen Hemminger
2019-05-16 7:10 ` David Marchand
2019-05-16 7:10 ` David Marchand
2019-05-15 22:19 ` [dpdk-dev] [RFC 2/4] net/ether: add eth_unformat_addr Stephen Hemminger
2019-05-15 22:19 ` Stephen Hemminger
2019-05-16 7:28 ` David Marchand
2019-05-16 7:28 ` David Marchand
2019-05-15 22:19 ` [dpdk-dev] [RFC 3/4] ethdev: use eth_unformat_addr Stephen Hemminger
2019-05-15 22:19 ` Stephen Hemminger
2019-05-16 7:32 ` David Marchand
2019-05-16 7:32 ` David Marchand
2019-05-16 10:19 ` Bruce Richardson
2019-05-16 10:19 ` Bruce Richardson
2019-05-15 22:19 ` [dpdk-dev] [RFC 4/4] net/ether: use bitops to speedup comparison Stephen Hemminger
2019-05-15 22:19 ` Stephen Hemminger
2019-05-16 9:03 ` Mattias Rönnblom [this message]
2019-05-16 9:03 ` Mattias Rönnblom
2019-05-16 15:32 ` Stephen Hemminger
2019-05-16 16:03 ` Bruce Richardson
2019-05-16 16:06 ` Stephen Hemminger
2019-05-16 16:07 ` Bruce Richardson
2019-05-16 16:36 ` Bruce Richardson
2019-05-16 17:04 ` Stephen Hemminger
2019-05-16 20:37 ` Bruce Richardson
2019-05-16 20:41 ` Bruce Richardson
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