From: "Van Haaren, Harry" <harry.van.haaren@intel.com>
To: Dell Will <coolwilled@hotmail.com>, users <users@dpdk.org>
Subject: Re: [dpdk-users] Why not prefetch the second cache line of struct rte_mbuf for better performance ?
Date: Tue, 26 Mar 2019 10:53:48 +0000 [thread overview]
Message-ID: <E923DB57A917B54B9182A2E928D00FA67580A0C4@IRSMSX102.ger.corp.intel.com> (raw)
In-Reply-To: <TY2PR04MB3808A8797DBB532510FDE6EDDF5F0@TY2PR04MB3808.apcprd04.prod.outlook.com>
> -----Original Message-----
> From: users [mailto:users-bounces@dpdk.org] On Behalf Of Dell Will
> Sent: Tuesday, March 26, 2019 9:04 AM
> To: users <users@dpdk.org>
> Subject: [dpdk-users] Why not prefetch the second cache line of struct
> rte_mbuf for better performance ?
>
> Hello, everybody
Hi,
> I find that many codes in DPDK only prefetch the first cache line of struct
> rte_mbuf.
> The struct rte_mbuf has 2 cache lines.
> Why not prefetch the second line ?
A reason that cache-line 2 is not always prefetched is that it is not
always going to be used.
For example, the packet RX routines modify only the 1-st cache line, and do
not require the 2nd to be available.
> Is it hinted that the CPU (x64 or ARM) always automatically prefetch the
> next immediately followed cache line ?
Some details on x86-64 prefetchers here, particularly the "Adjacent Cache-Line Prefetch" is of interest;
https://software.intel.com/en-us/articles/optimizing-application-performance-on-intel-coret-microarchitecture-using-hardware-implemented-prefetchers
[Side note, x64 is actually a different architecture than x86-64].
> Thanks a lot !
Hope that helps, -Harry
prev parent reply other threads:[~2019-03-26 10:53 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-26 9:03 Dell Will
2019-03-26 10:53 ` Van Haaren, Harry [this message]
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