From: Olivier MATZ <olivier.matz@6wind.com>
To: Cyril Chemparathy <cchemparathy@ezchip.com>, dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 00/10] Improve cast alignment for strict aligned machines
Date: Mon, 04 May 2015 11:50:09 +0200 [thread overview]
Message-ID: <554740D1.4050104@6wind.com> (raw)
In-Reply-To: <1430324134-25654-1-git-send-email-cchemparathy@ezchip.com>
Hi Cyril,
On 04/29/2015 06:15 PM, Cyril Chemparathy wrote:
> This series contains a few improvements that allow the DPDK code base to build
> properly on machines that enforce strict pointer cast alignment constraints.
>
> When dealing with packet data which could be arbitrarily aligned, we get the
> compiler to do the right thing by (a) making sure that header types are
> packed, and (b) introducing and using unaligned_uint(16|32|64)_t types when
> upcasting from byte pointers.
>
> In a few other instances, we know apriori that the pointer cast cannot
> possibly break alignment. This applies to the changes in mempool, hash, mbuf,
> and the ethdev stats code. Here, we simply silence the compiler by casting
> through (void *) using the RTE_PTR_(ADD|SUB) macros.
>
> Finally, we introduce a new rte_pktmbuf_mtod_offset() helper to return a type
> casted pointer to an offset within the packet data. This replaces the
> following commonly used pattern:
> (struct foo *)(rte_pktmbuf_mtod(m, char *) + offset)
> with:
> rte_pktmbuf_mtod_offset(m, struct foo *, offset)
> To ensure consistency, the above transform was applied throughout the code
> base using the coccinelle semantic patching tool.
>
Before diving into the patches, I'm wondering if adding aligned(1) or
(packed) attribute at some places would have a performance impact on
supported architectures (Intel or IBM Power). Did you manage to test
it?
Regards,
Olivier
next prev parent reply other threads:[~2015-05-04 9:50 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-29 16:15 Cyril Chemparathy
2015-04-29 16:15 ` [dpdk-dev] [PATCH 01/10] eal: add and use unaligned integer types Cyril Chemparathy
2015-06-19 15:58 ` Olivier MATZ
2015-06-19 17:18 ` Cyril Chemparathy
2015-04-29 16:15 ` [dpdk-dev] [PATCH 02/10] mempool: silence -Wcast-align on pointer arithmetic Cyril Chemparathy
2015-04-29 16:15 ` [dpdk-dev] [PATCH 03/10] hash: " Cyril Chemparathy
2015-04-29 16:15 ` [dpdk-dev] [PATCH 04/10] mbuf: " Cyril Chemparathy
2015-04-29 16:15 ` [dpdk-dev] [PATCH 05/10] ethdev: " Cyril Chemparathy
2015-04-29 16:15 ` [dpdk-dev] [PATCH 06/10] app/test-pmd: pack simple_gre_hdr Cyril Chemparathy
2015-04-29 16:15 ` [dpdk-dev] [PATCH 07/10] app/test: use struct ether_addr instead of a byte array cast Cyril Chemparathy
2015-04-29 16:15 ` [dpdk-dev] [PATCH 08/10] librte_mbuf: Add rte_pktmbuf_mtod_offset() Cyril Chemparathy
2015-06-19 15:58 ` Olivier MATZ
2015-06-19 17:18 ` Cyril Chemparathy
2015-04-29 16:15 ` [dpdk-dev] [PATCH 09/10] librte_mbuf: Add transform for rte_pktmbuf_mtod_offset() Cyril Chemparathy
2015-04-29 16:15 ` [dpdk-dev] [PATCH 10/10] librte_mbuf: Apply mtod-offset.cocci transform Cyril Chemparathy
2015-05-04 9:50 ` Olivier MATZ [this message]
2015-05-04 17:26 ` [dpdk-dev] [PATCH 00/10] Improve cast alignment for strict aligned machines Cyril Chemparathy
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=554740D1.4050104@6wind.com \
--to=olivier.matz@6wind.com \
--cc=cchemparathy@ezchip.com \
--cc=dev@dpdk.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).