From: "Wang, Zhihong" <zhihong.wang@intel.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 0/4] Optimize memcpy for AVX512 platforms
Date: Fri, 15 Jan 2016 06:39:01 +0000 [thread overview]
Message-ID: <8F6C2BD409508844A0EFC19955BE0941033A63DA@SHSMSX103.ccr.corp.intel.com> (raw)
In-Reply-To: <20160114084832.672fac86@xeon-e3>
> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Friday, January 15, 2016 12:49 AM
> To: Wang, Zhihong <zhihong.wang@intel.com>
> Cc: dev@dpdk.org; Ananyev, Konstantin <konstantin.ananyev@intel.com>;
> Richardson, Bruce <bruce.richardson@intel.com>; Xie, Huawei
> <huawei.xie@intel.com>
> Subject: Re: [PATCH 0/4] Optimize memcpy for AVX512 platforms
>
> On Thu, 14 Jan 2016 01:13:18 -0500
> Zhihong Wang <zhihong.wang@intel.com> wrote:
>
> > This patch set optimizes DPDK memcpy for AVX512 platforms, to make full
> > utilization of hardware resources and deliver high performance.
> >
> > In current DPDK, memcpy holds a large proportion of execution time in
> > libs like Vhost, especially for large packets, and this patch can bring
> > considerable benefits.
> >
> > The implementation is based on the current DPDK memcpy framework, some
> > background introduction can be found in these threads:
> > http://dpdk.org/ml/archives/dev/2014-November/008158.html
> > http://dpdk.org/ml/archives/dev/2015-January/011800.html
> >
> > Code changes are:
> >
> > 1. Read CPUID to check if AVX512 is supported by CPU
> >
> > 2. Predefine AVX512 macro if AVX512 is enabled by compiler
> >
> > 3. Implement AVX512 memcpy and choose the right implementation based
> on
> > predefined macros
> >
> > 4. Decide alignment unit for memcpy perf test based on predefined macros
> >
> > Zhihong Wang (4):
> > lib/librte_eal: Identify AVX512 CPU flag
> > mk: Predefine AVX512 macro for compiler
> > lib/librte_eal: Optimize memcpy for AVX512 platforms
> > app/test: Adjust alignment unit for memcpy perf test
> >
> > app/test/test_memcpy_perf.c | 6 +
> > .../common/include/arch/x86/rte_cpuflags.h | 2 +
> > .../common/include/arch/x86/rte_memcpy.h | 247
> ++++++++++++++++++++-
> > mk/rte.cpuflags.mk | 4 +
> > 4 files changed, 255 insertions(+), 4 deletions(-)
> >
>
> This really looks like code that could benefit from Gcc
> function multiversioning. The current cpuflags model is useless/flawed
> in real product deployment
I've tried gcc function multi versioning, with a simple add() function
which returns a + b, and a loop calling it for millions of times. Turned
out this mechanism adds 17% extra time to execute, overall it's a lot
of extra overhead.
Quote the gcc wiki: "GCC takes care of doing the dispatching to call
the right version at runtime". So it loses inlining and adds extra
dispatching overhead.
Also this mechanism works only for C++, right?
I think using predefined macros at compile time is more efficient and
suits DPDK more.
Could you please give an example when the current CPU flags model
stop working? So I can fix it.
next prev parent reply other threads:[~2016-01-15 6:39 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-14 6:13 Zhihong Wang
2016-01-14 6:13 ` [dpdk-dev] [PATCH 1/4] lib/librte_eal: Identify AVX512 CPU flag Zhihong Wang
2016-01-14 6:13 ` [dpdk-dev] [PATCH 2/4] mk: Predefine AVX512 macro for compiler Zhihong Wang
2016-01-14 6:13 ` [dpdk-dev] [PATCH 3/4] lib/librte_eal: Optimize memcpy for AVX512 platforms Zhihong Wang
2016-01-14 6:13 ` [dpdk-dev] [PATCH 4/4] app/test: Adjust alignment unit for memcpy perf test Zhihong Wang
2016-01-14 16:48 ` [dpdk-dev] [PATCH 0/4] Optimize memcpy for AVX512 platforms Stephen Hemminger
2016-01-15 6:39 ` Wang, Zhihong [this message]
2016-01-15 22:03 ` Vincent JARDIN
2016-01-18 3:05 ` [dpdk-dev] [PATCH v2 0/5] " Zhihong Wang
2016-01-18 3:05 ` [dpdk-dev] [PATCH v2 1/5] lib/librte_eal: Identify AVX512 CPU flag Zhihong Wang
2016-01-18 3:05 ` [dpdk-dev] [PATCH v2 2/5] mk: Predefine AVX512 macro for compiler Zhihong Wang
2016-01-18 3:05 ` [dpdk-dev] [PATCH v2 3/5] lib/librte_eal: Optimize memcpy for AVX512 platforms Zhihong Wang
2016-01-18 3:05 ` [dpdk-dev] [PATCH v2 4/5] app/test: Adjust alignment unit for memcpy perf test Zhihong Wang
2016-01-18 3:05 ` [dpdk-dev] [PATCH v2 5/5] lib/librte_eal: Tune memcpy for prior platforms Zhihong Wang
2016-01-18 20:06 ` [dpdk-dev] [PATCH v2 0/5] Optimize memcpy for AVX512 platforms Stephen Hemminger
2016-01-19 2:37 ` Wang, Zhihong
2016-01-27 15:23 ` Thomas Monjalon
2016-01-28 6:09 ` Wang, Zhihong
2016-01-27 15:30 ` Thomas Monjalon
2016-01-27 18:48 ` Ananyev, Konstantin
2016-01-27 20:18 ` Thomas Monjalon
2017-08-30 9:37 ` linhaifeng
2017-09-18 5:10 ` Wang, Zhihong
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