From: Bruce Richardson <bruce.richardson@intel.com>
To: Mike Stolarchuk <mike.stolarchuk@bigswitch.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] What's the point of RTE_MBUF_PREFETCH_TO_FREE()?
Date: Mon, 6 Nov 2017 09:25:41 +0000 [thread overview]
Message-ID: <20171106092541.GA21408@bricha3-MOBL3.ger.corp.intel.com> (raw)
In-Reply-To: <CA+Qp4XwDBVuFBoJe2xsw74PV+=K_2F5XxfOw9UqoLH072npbiQ@mail.gmail.com>
On Fri, Nov 03, 2017 at 01:28:18PM -0700, Mike Stolarchuk wrote:
> It seems to be used to prefetch the mbuf in preparation for a free of an
> mbuf.
>
> But RTE_MBUF_PREFETCH_TO_FREE() currently does a prefetch for the
> ffirst cache line in the mbuf, but doesn't a free do a put to the mbuf's
> mempool?
>
> And isn't the mempool reference in the mbuf's second cache line?
>
Yes, that looks like a bug. Doing "git blame" shows that that macro
comes from the original versions of DPDK pre-dpdk.org, and hasn't been
modified since, so it was missed when the mbuf was expanded from 1 line
to 2. I also note that the high-performance ixgbe/i40e vector drivers do
not use this macro, only the slow paths in those drivers do, so I wonder
if it can be removed. If not, it should be fixed.
/Bruce
prev parent reply other threads:[~2017-11-06 9:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-03 20:28 Mike Stolarchuk
2017-11-06 9:25 ` Bruce Richardson [this message]
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