From: "Mattias Rönnblom" <hofors@lysator.liu.se>
To: "Morten Brørup" <mb@smartsharesystems.com>,
emil.berg@ericsson.com, bruce.richardson@intel.com, dev@dpdk.org
Cc: stephen@networkplumber.org, stable@dpdk.org, bugzilla@dpdk.org,
olivier.matz@6wind.com
Subject: Re: [PATCH v4] net: fix checksum with unaligned buffer
Date: Mon, 27 Jun 2022 14:28:27 +0200 [thread overview]
Message-ID: <9f543fc0-ae8a-067b-d13f-38a0503dd619@lysator.liu.se> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35D87169@smartserver.smartshare.dk>
On 2022-06-23 14:51, Morten Brørup wrote:
>> From: Morten Brørup [mailto:mb@smartsharesystems.com]
>> Sent: Thursday, 23 June 2022 14.39
>>
>> With this patch, the checksum can be calculated on an unaligned buffer.
>> I.e. the buf parameter is no longer required to be 16 bit aligned.
>>
>> The checksum is still calculated using a 16 bit aligned pointer, so the
>> compiler can auto-vectorize the function's inner loop.
>>
>> When the buffer is unaligned, the first byte of the buffer is handled
>> separately. Furthermore, the calculated checksum of the buffer is byte
>> shifted before being added to the initial checksum, to compensate for
>> the
>> checksum having been calculated on the buffer shifted by one byte.
>>
>> v4:
>> * Add copyright notice.
>> * Include stdbool.h (Emil Berg).
>> * Use RTE_PTR_ADD (Emil Berg).
>> * Fix one more typo in commit message. Is 'unligned' even a word?
>> v3:
>> * Remove braces from single statement block.
>> * Fix typo in commit message.
>> v2:
>> * Do not assume that the buffer is part of an aligned packet buffer.
>>
>> Bugzilla ID: 1035
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
>> ---
>> lib/net/rte_ip.h | 32 +++++++++++++++++++++++++++-----
>> 1 file changed, 27 insertions(+), 5 deletions(-)
>>
>> diff --git a/lib/net/rte_ip.h b/lib/net/rte_ip.h
>> index b502481670..738d643da0 100644
>> --- a/lib/net/rte_ip.h
>> +++ b/lib/net/rte_ip.h
>> @@ -3,6 +3,7 @@
>> * The Regents of the University of California.
>> * Copyright(c) 2010-2014 Intel Corporation.
>> * Copyright(c) 2014 6WIND S.A.
>> + * Copyright(c) 2022 SmartShare Systems.
>> * All rights reserved.
>> */
>>
>> @@ -15,6 +16,7 @@
>> * IP-related defines
>> */
>>
>> +#include <stdbool.h>
>> #include <stdint.h>
>>
>> #ifdef RTE_EXEC_ENV_WINDOWS
>> @@ -162,20 +164,40 @@ __rte_raw_cksum(const void *buf, size_t len,
>> uint32_t sum)
>> {
>> /* extend strict-aliasing rules */
>> typedef uint16_t __attribute__((__may_alias__)) u16_p;
>> - const u16_p *u16_buf = (const u16_p *)buf;
>> - const u16_p *end = u16_buf + len / sizeof(*u16_buf);
>> + const u16_p *u16_buf;
>> + const u16_p *end;
>> + uint32_t bsum = 0;
>> + const bool unaligned = (uintptr_t)buf & 1;
>> +
>> + /* if buffer is unaligned, keeping it byte order independent */
>> + if (unlikely(unaligned)) {
>> + uint16_t first = 0;
>> + if (unlikely(len == 0))
>> + return 0;
>> + ((unsigned char *)&first)[1] = *(const unsigned char *)buf;
>> + bsum += first;
>> + buf = RTE_PTR_ADD(buf, 1);
>> + len--;
>> + }
>>
>> + /* aligned access for compiler auto-vectorization */
The compiler will be able to auto vectorize even unaligned accesses,
just with different instructions. From what I can tell, there's no
performance impact, at least not on the x86_64 systems I tried on.
I think you should remove the first special case conditional and use
memcpy() instead of the cumbersome __may_alias__ construct to retrieve
the data.
>> + u16_buf = (const u16_p *)buf;
>> + end = u16_buf + len / sizeof(*u16_buf);
>> for (; u16_buf != end; ++u16_buf)
>> - sum += *u16_buf;
>> + bsum += *u16_buf;
>>
>> /* if length is odd, keeping it byte order independent */
>> if (unlikely(len % 2)) {
>> uint16_t left = 0;
>> *(unsigned char *)&left = *(const unsigned char *)end;
>> - sum += left;
>> + bsum += left;
>> }
>>
>> - return sum;
>> + /* if buffer is unaligned, swap the checksum bytes */
>> + if (unlikely(unaligned))
>> + bsum = (bsum & 0xFF00FF00) >> 8 | (bsum & 0x00FF00FF) << 8;
>> +
>> + return sum + bsum;
>> }
>>
>> /**
>> --
>> 2.17.1
>
> @Emil, thank you for thoroughly reviewing the previous versions.
>
> If your test succeeds and you are satisfied with the patch, remember to reply with a "Tested-by" tag for patchwork.
>
next prev parent reply other threads:[~2022-06-27 12:28 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-15 7:16 [Bug 1035] __rte_raw_cksum() crash with misaligned pointer bugzilla
2022-06-15 14:40 ` Morten Brørup
2022-06-16 5:44 ` Emil Berg
2022-06-16 6:27 ` Morten Brørup
2022-06-16 6:32 ` Emil Berg
2022-06-16 6:44 ` Morten Brørup
2022-06-16 13:58 ` Mattias Rönnblom
2022-06-16 14:36 ` Morten Brørup
2022-06-17 7:32 ` Morten Brørup
2022-06-17 8:45 ` [PATCH] net: fix checksum with unaligned buffer Morten Brørup
2022-06-17 9:06 ` Morten Brørup
2022-06-17 12:17 ` Emil Berg
2022-06-20 10:37 ` Emil Berg
2022-06-20 10:57 ` Morten Brørup
2022-06-21 7:16 ` Emil Berg
2022-06-21 8:05 ` Morten Brørup
2022-06-21 8:23 ` Bruce Richardson
2022-06-21 9:35 ` Morten Brørup
2022-06-22 6:26 ` Emil Berg
2022-06-22 9:18 ` Bruce Richardson
2022-06-22 11:26 ` Morten Brørup
2022-06-22 12:25 ` Emil Berg
2022-06-22 14:01 ` Morten Brørup
2022-06-22 14:03 ` Emil Berg
2022-06-23 5:21 ` Emil Berg
2022-06-23 7:01 ` Morten Brørup
2022-06-23 11:39 ` Emil Berg
2022-06-23 12:18 ` Morten Brørup
2022-06-22 13:44 ` [PATCH v2] " Morten Brørup
2022-06-22 13:54 ` [PATCH v3] " Morten Brørup
2022-06-23 12:39 ` [PATCH v4] " Morten Brørup
2022-06-23 12:51 ` Morten Brørup
2022-06-27 7:56 ` Emil Berg
2022-06-27 10:54 ` Morten Brørup
2022-06-27 12:28 ` Mattias Rönnblom [this message]
2022-06-27 12:46 ` Emil Berg
2022-06-27 12:50 ` Emil Berg
2022-06-27 13:22 ` Morten Brørup
2022-06-27 17:22 ` Mattias Rönnblom
2022-06-27 20:21 ` Morten Brørup
2022-06-28 6:28 ` Mattias Rönnblom
2022-06-30 16:28 ` Morten Brørup
2022-07-07 15:21 ` Stanisław Kardach
2022-07-07 18:34 ` [PATCH 1/2] app/test: add cksum performance test Mattias Rönnblom
2022-07-07 18:34 ` [PATCH 2/2] net: have checksum routines accept unaligned data Mattias Rönnblom
2022-07-07 21:44 ` Morten Brørup
2022-07-08 12:43 ` Mattias Rönnblom
2022-07-08 12:56 ` [PATCH v2 1/2] app/test: add cksum performance test Mattias Rönnblom
2022-07-08 12:56 ` [PATCH v2 2/2] net: have checksum routines accept unaligned data Mattias Rönnblom
2022-07-08 14:44 ` Ferruh Yigit
2022-07-11 9:53 ` Olivier Matz
2022-07-11 10:53 ` Mattias Rönnblom
2022-07-11 9:47 ` [PATCH v2 1/2] app/test: add cksum performance test Olivier Matz
2022-07-11 10:42 ` Mattias Rönnblom
2022-07-11 11:33 ` Olivier Matz
2022-07-11 12:11 ` [PATCH v3 " Mattias Rönnblom
2022-07-11 12:11 ` [PATCH v3 2/2] net: have checksum routines accept unaligned data Mattias Rönnblom
2022-07-11 13:25 ` Olivier Matz
2022-08-08 9:25 ` Mattias Rönnblom
2022-09-20 12:09 ` Mattias Rönnblom
2022-09-20 16:10 ` Thomas Monjalon
2022-07-11 13:20 ` [PATCH v3 1/2] app/test: add cksum performance test Olivier Matz
2022-07-08 13:02 ` [PATCH 2/2] net: have checksum routines accept unaligned data Morten Brørup
2022-07-08 13:52 ` Mattias Rönnblom
2022-07-08 14:10 ` Bruce Richardson
2022-07-08 14:30 ` Morten Brørup
2022-06-30 17:41 ` [PATCH v4] net: fix checksum with unaligned buffer Stephen Hemminger
2022-06-30 17:45 ` Stephen Hemminger
2022-07-01 4:11 ` Emil Berg
2022-07-01 16:50 ` Morten Brørup
2022-07-01 17:04 ` Stephen Hemminger
2022-07-01 20:46 ` Morten Brørup
2022-06-16 14:09 ` [Bug 1035] __rte_raw_cksum() crash with misaligned pointer Mattias Rönnblom
2022-10-10 10:40 ` bugzilla
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=9f543fc0-ae8a-067b-d13f-38a0503dd619@lysator.liu.se \
--to=hofors@lysator.liu.se \
--cc=bruce.richardson@intel.com \
--cc=bugzilla@dpdk.org \
--cc=dev@dpdk.org \
--cc=emil.berg@ericsson.com \
--cc=mb@smartsharesystems.com \
--cc=olivier.matz@6wind.com \
--cc=stable@dpdk.org \
--cc=stephen@networkplumber.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).