linux-kernel - Re: [PATCH 0/3] Optimize code generation during context

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Message-ID: <20251030150417.684-1-qq570070308@gmail.com>
Date: Thu, 30 Oct 2025 23:04:17 +0800
From: Xie Yuanbin <qq570070308@...il.com>
To: david@...hat.com
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Subject: Re: [PATCH 0/3] Optimize code generation during context

On Wed, 29 Oct 2025 11:26:39 +0100, David Hildenbrand wrote:
>> I did some testing using my devices,
>> and the testing logic is as follows:
>> ```
>> -	return finish_task_switch(prev);
>> +	start_time = rdtsc();
>> +	barrier();
>> +	rq = finish_task_switch(prev);
>> +	barrier();
>> +	end_time = rdtsc;
>> +	return rq;
>> ```
>>
>> The test data is as follows:
>> 1. mitigations Off, without patches: 13.5 - 13.7
>> 2. mitigations Off, with patches: 13.5 - 13.7
>> 3. mitigations On, without patches: 23.3 - 23.6
>> 4. mitigations On, with patches: 16.6 - 16.8
>
> Such numbers absolutely have to be part of the relevant patches / cover
> letter to show that the compiler is not actually smart enough to make a
> good decision.

This was indeed my oversight; I did not read the submitting-patches
documentation carefully, thank you for your pointing it out, and I deeply
apologize for this.

Do I need to send the V2 version patches to supplement the relevant data?

By the way, the above data was tested in WSL. I did a more detailed test
on a physical machine. If possible, this data may be more appropriate:
Link: https://lore.kernel.org/20251027152100.62906-1-qq570070308@gmail.com

> Cheers
>
> David / dhildenb

Thanks very much.

Xie Yuanbin