linux-kernel - Re: This is the fourth time I’ve tried to find what led to the regression of outgoing network speed and each time I find the merge commit 8c94ccc7cd691472461448f98e2372c75849406c

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Message-ID: <87cyte1hfk.fsf@nvidia.com>
Date: Fri, 02 Feb 2024 17:08:02 -0800
From: Rahul Rameshbabu <rrameshbabu@...dia.com>
To: Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
Cc: Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
 linux-netdev@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>
Subject: Re: This is the fourth time I’ve tried to find
 what led to the
 regression of outgoing network speed and each time I find the merge commit
 8c94ccc7cd691472461448f98e2372c75849406c

On Sat, 03 Feb, 2024 06:02:15 +0500 Mikhail Gavrilov <mikhail.v.gavrilov@...il.com> wrote:
> Hi,
> I'm trying to find the first bad commit that led to a decreased
> network outgoing speed.
> And every time I come to a huge merge [Merge tag 'usb-6.8-rc1' of
> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb]
> I have already triple-checked all my answers and speed measurements.
> I don't understand where I'm making a mistake.

Have you tried using --first-parent when you git bisect to see if that
helps you find the culprit aside from the merge commit you keep hitting?

https://git-scm.com/docs/git-bisect#Documentation/git-bisect.txt---first-parent

>
> Let's try to figure it out together.
>
> Input data:
> Two computers connected 1Gbps link.
> Both have the same hardware.
> Network: RTL8125 2.5GbE Controller (rev 05)
>
> When I copy files from one computer to another and kernel snapshot
> builded from commit 296455ade1fd I have 97-110MB/sec which is almost
> max speed of 1Gbps link.
> When I move to commit 9d1694dc91ce I have only 66-70MB/sec which is
> significantly slower.
>
> I bisected the issue by measuring network speed on each step.
> I save all results to file [1]
>
> [1] file is attached as a zip archive.
>
> # first bad commit: [8c94ccc7cd691472461448f98e2372c75849406c] Merge
> tag 'usb-6.8-rc1' of
> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb

--
Thanks,

Rahul Rameshbabu