From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: Olivier MATZ <olivier.matz@6wind.com>,
"Hanoch Haim (hhaim)" <hhaim@cisco.com>
Cc: Ilya Matveychikov <matvejchikov@gmail.com>,
"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v3] mbuf: cleanup rte_pktmbuf_lastseg(), fix atomic usage
Date: Thu, 16 Nov 2017 10:54:34 +0000 [thread overview]
Message-ID: <2601191342CEEE43887BDE71AB9772585FABD995@irsmsx105.ger.corp.intel.com> (raw)
In-Reply-To: <20171115173058.mrkrv3usbl5sfw3h@platinum>
Hi Olivier,
> I agree with Konstantin's comment done in another thread [1]:
>
> '''
> That would cause extra read; cmp (and possible slowdown) for atomic refcnt.
> If that really need to be fixed - probably we need to introduce a new function
> that would do update without trying to read refctn first - rte_mbuf_refcnt_update_blind() or so.
> '''
>
> However I'm not sure a new function is really needed: the name is not ideal,
That was just the first one from top of my head :)
If the issue in naming only - I suppose we can find something better.
Personally I like Ilya's one: __rte_mbuf_refcnt_update().
> and it would only be used once. What about the patch below?
It would do the job too, but looks a bit clumsy to me.
Konstantin
>
> ==============================
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -1361,8 +1361,18 @@ rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
>
> return m;
>
> - } else if (rte_atomic16_add_return(&m->refcnt_atomic, -1) == 0) {
> + } else {
>
> + /* We don't use rte_mbuf_refcnt_update() because we already
> + * tested that refcnt != 1.
> + */
> +#ifdef RTE_MBUF_REFCNT_ATOMIC
> + ret = rte_atomic16_add_return(&m->refcnt_atomic, -1);
> +#else
> + ret = --m->refcnt;
> +#endif
> + if (ret != 0)
> + return NULL;
>
> if (RTE_MBUF_INDIRECT(m))
> rte_pktmbuf_detach(m);
> @@ -1375,7 +1385,6 @@ rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
>
> return m;
> }
> - return NULL;
> }
>
> /* deprecated, replaced by rte_pktmbuf_prefree_seg() */
> ==============================
>
> [1] http://dpdk.org/dev/patchwork/patch/31378/
>
>
> Regards,
> Olivier
next prev parent reply other threads:[~2017-11-16 10:54 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-15 9:14 Hanoh Haim
2017-11-15 11:13 ` Ilya Matveychikov
2017-11-15 12:46 ` Hanoch Haim (hhaim)
2017-11-15 17:30 ` Olivier MATZ
2017-11-16 7:16 ` Hanoch Haim (hhaim)
2017-11-16 8:07 ` Ilya Matveychikov
2017-11-16 8:42 ` Olivier MATZ
2017-11-16 9:06 ` Hanoch Haim (hhaim)
2017-11-16 9:32 ` Ilya Matveychikov
2017-11-16 9:37 ` Olivier MATZ
2017-11-16 9:44 ` Ilya Matveychikov
2017-11-16 10:54 ` Ananyev, Konstantin [this message]
2017-12-08 15:46 ` [dpdk-dev] [PATCH v4] mbuf: fix mbuf free performance with non atomic refcnt Olivier Matz
2017-12-08 16:04 ` Ilya Matveychikov
2017-12-08 16:19 ` Olivier MATZ
2017-12-08 16:37 ` Stephen Hemminger
2017-12-10 8:37 ` Hanoch Haim (hhaim)
2017-12-11 10:28 ` Olivier MATZ
2018-01-18 23:23 ` Thomas Monjalon
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