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From: Olivier MATZ <olivier.matz@6wind.com>
To: Neil Horman <nhorman@tuxdriver.com>, Jia Yu <jyu@vmware.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] lib: include rte_memory.h for __rte_cache_aligned
Date: Tue, 09 Dec 2014 09:53:18 +0100
Message-ID: <5486B87E.5010404@6wind.com> (raw)
In-Reply-To: <20141208150401.GB3907@localhost.localdomain>

Hi Neil,

On 12/08/2014 04:04 PM, Neil Horman wrote:
> On Fri, Nov 07, 2014 at 09:28:09AM -0800, Jia Yu wrote:
>> Include rte_memory.h for lib files that use __rte_cache_aligned
>> attribute.
>> Signed-off-by: Jia Yu <jyu@vmware.com>
> Why?  I presume there was a build break or something.  Please repost with a
> changelog that details what this patch is for.
> Neil

I don't know if Yu's issue was the same, but I had a very "fun" issue
with __rte_cache_aligned in my application. Consider the following code:

	struct per_core_foo {
	} __rte_cache_aligned;

	struct global_foo {
		struct per_core_foo foo[RTE_MAX_CORE];

If __rte_cache_aligned is not defined (rte_memory.h is not included),
the code compiles but the structure is not aligned... it defines the
structure and creates a global variable called __rte_cache_aligned.
And this can lead to really bad things if this code is in a .h that
is included by files that may or may not include rte_memory.h

I have no idea about how we could prevent this issue, except using
__attribute__((aligned(CACHE_LINE))) instead of __rte_cache_aligned.

Anyway this could probably explain the willing to include rte_memory.h


  reply	other threads:[~2014-12-09  8:53 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-07 17:28 [dpdk-dev] [PATCH] " Jia Yu
2014-11-10  9:46 ` Thomas Monjalon
2014-11-17 19:07   ` Jia Yu
2014-12-08 15:04 ` [dpdk-dev] " Neil Horman
2014-12-09  8:53   ` Olivier MATZ [this message]
2014-12-09  9:11     ` Jia Yu
2014-12-09 15:22     ` Neil Horman
2014-12-10 19:09       ` Jia Yu
2014-12-11  0:28         ` Neil Horman
2014-12-11  0:36           ` Thomas Monjalon
2014-12-11 14:17             ` Neil Horman
2014-12-11 21:14               ` Thomas Monjalon
2014-12-11  0:51       ` Thomas Monjalon

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