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: <881d47bf-5f5d-49d6-9502-3b22899eb253@infradead.org>
Date: Fri, 2 Feb 2024 17:16:41 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>,
 Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
 Greg KH <gregkh@...uxfoundation.org>,
 Network Development <netdev@...r.kernel.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

[correct the netdev mailing list address]


On 2/2/24 17:15, Randy Dunlap wrote:
> 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