From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: "Verkamp, Daniel" <daniel.verkamp@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>
Cc: "Richardson, Bruce" <bruce.richardson@intel.com>
Subject: Re: [dpdk-dev] [PATCH v2] ring: use aligned memzone allocation
Date: Sat, 3 Jun 2017 10:00:06 +0000 [thread overview]
Message-ID: <2601191342CEEE43887BDE71AB9772583FB05216@IRSMSX109.ger.corp.intel.com> (raw)
In-Reply-To: <A5F28D4A728A7E41839CDC5C3B5A01E87EA1B586@FMSMSX103.amr.corp.intel.com>
>
> The PROD/CONS_ALIGN values on x86-64 are set to 2 cache lines, so members of struct rte_ring are 128 byte aligned,
>and therefore the whole struct needs 128-byte alignment according to the ABI so that the 128-byte alignment of the fields can be guaranteed.
Ah ok, missed the fact that rte_ring is 128B aligned these days.
BTW, I probably missed the initial discussion, but what was the reason for that?
Konstantin
>
> If the allocation is only 64-byte aligned, the beginning of the prod and cons fields may not actually be 128-byte aligned (but we've told the
> compiler that they are using the __rte_aligned macro). Accessing these fields when they are misaligned will work in practice on x86 (as long
> as the compiler doesn't use e.g. aligned SSE instructions), but it is undefined behavior according to the C standard, and UBSan (-
> fsanitize=undefined) checks for this.
>
> Thanks,
> -- Daniel Verkamp
>
> > -----Original Message-----
> > From: Ananyev, Konstantin
> > Sent: Friday, June 2, 2017 1:52 PM
> > To: Verkamp, Daniel <daniel.verkamp@intel.com>; dev@dpdk.org
> > Cc: Verkamp, Daniel <daniel.verkamp@intel.com>
> > Subject: RE: [dpdk-dev] [PATCH v2] ring: use aligned memzone allocation
> >
> >
> >
> > > -----Original Message-----
> > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Daniel Verkamp
> > > Sent: Friday, June 2, 2017 9:12 PM
> > > To: dev@dpdk.org
> > > Cc: Verkamp, Daniel <daniel.verkamp@intel.com>
> > > Subject: [dpdk-dev] [PATCH v2] ring: use aligned memzone allocation
> > >
> > > rte_memzone_reserve() provides cache line alignment, but
> > > struct rte_ring may require more than cache line alignment: on x86-64,
> > > it needs 128-byte alignment due to PROD_ALIGN and CONS_ALIGN, which are
> > > 128 bytes, but cache line size is 64 bytes.
> >
> > Hmm but what for?
> > I understand we need our rte_ring cche-line aligned,
> > but why do you want it 2 cache-line aligned?
> > Konstantin
> >
> > >
> > > Fixes runtime warnings with UBSan enabled.
> > >
> > > Fixes: d9f0d3a1ffd4 ("ring: remove split cacheline build setting")
> > >
> > > Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>
> > > ---
> > >
> > > v2: fixed checkpatch warnings
> > >
> > > lib/librte_ring/rte_ring.c | 3 ++-
> > > 1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/lib/librte_ring/rte_ring.c b/lib/librte_ring/rte_ring.c
> > > index 5f98c33..6f58faf 100644
> > > --- a/lib/librte_ring/rte_ring.c
> > > +++ b/lib/librte_ring/rte_ring.c
> > > @@ -189,7 +189,8 @@ rte_ring_create(const char *name, unsigned count, int
> > socket_id,
> > > /* reserve a memory zone for this ring. If we can't get rte_config or
> > > * we are secondary process, the memzone_reserve function will set
> > > * rte_errno for us appropriately - hence no check in this this function */
> > > - mz = rte_memzone_reserve(mz_name, ring_size, socket_id, mz_flags);
> > > + mz = rte_memzone_reserve_aligned(mz_name, ring_size, socket_id,
> > > + mz_flags, __alignof__(*r));
> > > if (mz != NULL) {
> > > r = mz->addr;
> > > /* no need to check return value here, we already checked the
> > > --
> > > 2.9.4
next prev parent reply other threads:[~2017-06-03 10:00 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-02 20:03 [dpdk-dev] [PATCH] " Daniel Verkamp
2017-06-02 20:12 ` [dpdk-dev] [PATCH v2] " Daniel Verkamp
2017-06-02 20:51 ` Ananyev, Konstantin
2017-06-02 22:24 ` Verkamp, Daniel
2017-06-03 10:00 ` Ananyev, Konstantin [this message]
2017-06-05 16:21 ` Verkamp, Daniel
2017-06-06 9:59 ` Ananyev, Konstantin
2017-06-06 12:42 ` Bruce Richardson
2017-06-06 13:19 ` Ananyev, Konstantin
2017-06-06 14:56 ` Bruce Richardson
2017-06-08 12:45 ` Olivier Matz
2017-06-08 13:20 ` Bruce Richardson
2017-06-08 14:05 ` Olivier Matz
2017-06-08 14:11 ` Bruce Richardson
2017-06-08 14:50 ` Ananyev, Konstantin
2017-06-08 15:24 ` Bruce Richardson
2017-06-08 15:35 ` Ananyev, Konstantin
2017-06-08 16:03 ` Bruce Richardson
2017-06-08 16:12 ` Ananyev, Konstantin
2017-06-08 16:20 ` Richardson, Bruce
2017-06-08 16:42 ` Ananyev, Konstantin
2017-06-09 9:02 ` Bruce Richardson
2017-06-12 9:02 ` Olivier Matz
2017-06-12 9:56 ` Bruce Richardson
2017-06-30 11:35 ` Olivier Matz
2017-06-09 12:47 ` Yerden Zhumabekov
2017-06-09 17:16 ` Stephen Hemminger
2017-06-09 17:28 ` Jerin Jacob
2017-06-10 8:16 ` Ananyev, Konstantin
2017-06-12 3:07 ` Jerin Jacob
2017-06-12 10:18 ` Ananyev, Konstantin
2017-06-12 10:34 ` Jerin Jacob
2017-06-12 11:09 ` Bruce Richardson
2017-06-12 11:41 ` Jerin Jacob
2017-06-12 12:17 ` Ananyev, Konstantin
2017-06-12 12:42 ` Jerin Jacob
2017-06-12 12:51 ` Ananyev, Konstantin
2017-06-12 13:06 ` Bruce Richardson
2017-06-12 13:20 ` Jerin Jacob
2017-06-30 11:36 ` Olivier Matz
2017-07-01 11:14 ` Thomas Monjalon
2017-07-01 11:25 ` Thomas Monjalon
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=2601191342CEEE43887BDE71AB9772583FB05216@IRSMSX109.ger.corp.intel.com \
--to=konstantin.ananyev@intel.com \
--cc=bruce.richardson@intel.com \
--cc=daniel.verkamp@intel.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).