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Message-Id: <4F646FBB-FE0B-4FEE-98E5-3CA2DF0598DE@oracle.com>
Date: Tue, 22 May 2018 13:29:53 -0600
From: William Kucharski <william.kucharski@...cle.com>
To: Alexander Duyck <alexander.duyck@...il.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Netdev <netdev@...r.kernel.org>,
intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
"Duyck, Alexander H" <alexander.h.duyck@...el.com>
Subject: Re: Regression: Approximate 34% performance hit in receive throughput
over ixgbe seen due to build_skb patch
> On May 22, 2018, at 12:23 PM, Alexander Duyck <alexander.duyck@...il.com> wrote:
>
> 3. There should be a private flag that can be updated via "ethtool
> --set-priv-flags" called "legacy-rx" that you can enable that will
> roll back to the original that did the copy-break type approach for
> small packets and the headers of the frame.
With legacy-rx enabled, most of the regression goes away, but it's still present
as compared to the code without the patch; the regression then drops to about 6%:
# ethtool --show-priv-flags eno1
Private flags for eno1:
legacy-rx: on
Socket Message Elapsed Messages
Size Size Time Okay Errors Throughput
bytes bytes secs # # 10^6bits/sec
65536 64 60.00 35934709 0 306.64
65536 60.00 33791739 288.35
Socket Message Elapsed Messages
Size Size Time Okay Errors Throughput
bytes bytes secs # # 10^6bits/sec
65536 64 60.00 39254351 0 334.97
65536 60.00 36761069 313.69
Is this variance to be expected, or do you think modification of the
interrupt delay would achieve better results?
William Kucharski
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