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From: Thomas Monjalon <thomas.monjalon@6wind.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>,
	Jianbo Liu <jianbo.liu@linaro.org>,
	Jerin Jacob <jerin.jacob@cavium.com>,
	Jan Viktorin <viktorin@rehivetech.com>,
	Chao Zhu <chaozhu@linux.vnet.ibm.com>
Cc: dev@dpdk.org, Tan Jianfeng <jianfeng.tan@intel.com>,
	Wang Zhihong <zhihong.wang@intel.com>,
	Olivier Matz <olivier.matz@6wind.com>,
	Maxime Coquelin <maxime.coquelin@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [dpdk-dev] [dpdk-stable] [PATCH 1/2] net/virtio: fix performance regression due to TSO enabling
Date: Wed, 11 Jan 2017 15:51:22 +0100	[thread overview]
Message-ID: <1610499.AMUobBPor6@xps13> (raw)
In-Reply-To: <1484108832-19907-2-git-send-email-yuanhan.liu@linux.intel.com>

2017-01-11 12:27, Yuanhan Liu:
> The fact that virtio net header is initiated to zero in PMD driver
> init stage means that these costly writes are unnecessary and could
> be avoided:
> 
>     if (hdr->csum_start != 0)
>         hdr->csum_start = 0;
> 
> And that's what the macro ASSIGN_UNLESS_EQUAL does. With this, the
> performance drop introduced by TSO enabling is recovered: it could
> be up to 20% in micro benchmarking.

This patch is adding a condition to assignments.
We need a benchmark on other architectures like ARM. Please anyone?


[...]
> +/* avoid write operation when necessary, to lessen cache issues */
> +#define ASSIGN_UNLESS_EQUAL(var, val) do {	\
> +	if ((var) != (val))			\
> +		(var) = (val);			\
> +} while (0)

  parent reply	other threads:[~2017-01-11 14:51 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-11  4:27 [dpdk-dev] [PATCH 0/2] net/virtio: optimize virtio net header reset Yuanhan Liu
2017-01-11  4:27 ` [dpdk-dev] [PATCH 1/2] net/virtio: fix performance regression due to TSO enabling Yuanhan Liu
2017-01-11  7:59   ` Maxime Coquelin
2017-01-11  8:08     ` Yuanhan Liu
2017-01-11  8:22     ` Olivier MATZ
2017-01-11 14:51   ` Thomas Monjalon [this message]
2017-01-12  2:30     ` [dpdk-dev] [dpdk-stable] " Yuanhan Liu
2017-01-12 15:02       ` Jan Viktorin
2017-01-13  6:13         ` Yuanhan Liu
2017-01-16  7:12           ` Yuanhan Liu
     [not found]             ` <46569522-b2c3-2a33-9111-049b73c79760@stud.fit.vutbr.cz>
     [not found]               ` <20170116111256.GA11439@yliu-dev.sh.intel.com>
     [not found]                 ` <8e8178c6-caa2-1b6e-10a0-c83820868db5@stud.fit.vutbr.cz>
2017-01-16 11:21                   ` Yuanhan Liu
     [not found]                     ` <a12848b4-76ef-29bc-f512-81bd8c1b9b76@stud.fit.vutbr.cz>
2017-01-30 13:30                       ` Yuanhan Liu
2017-01-30 13:54                         ` Maxime Coquelin
2017-01-30 14:10                           ` Yuanhan Liu
2017-01-11  4:27 ` [dpdk-dev] [PATCH 2/2] net/virtio: optimize header reset on any layout Yuanhan Liu
2017-01-11  8:01   ` Maxime Coquelin

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