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Date: Fri, 2 Feb 2024 17:15:30 -0800
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To: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>,
 Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
 linux-netdev@vger.kernel.org, Greg KH <gregkh@linuxfoundation.org>
References: <CABXGCsNnUfCCYVSb_-j-a-cAdONu1r6Fe8p2OtQ5op_wskOfpw@mail.gmail.com>
From: Randy Dunlap <rdunlap@infradead.org>
In-Reply-To: <CABXGCsNnUfCCYVSb_-j-a-cAdONu1r6Fe8p2OtQ5op_wskOfpw@mail.gmail.com>
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Hi,

On 2/2/24 17:02, Mikhail Gavrilov 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.
> 
> 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

a. Do you clean the object files between each test run?
or at least clean net/* and drivers/net/ethernet/* ?

b. I am far from a git expert, but in the bisects that I have
done, after each test run, I just say
$ git bisect good
or
$ git bisect bad

It looks like you are typing
$ git bisect [good | bad] hashID

Is that correct?

Anyway, I am interested in your outcome just to learn
how to handle this problem.

Good luck.

-- 
#Randy