linux-kernel - Re: [PATCH next] softirq: enable MAX_SOFTIRQ_TIME tuning with sysctl max_softirq_time

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Date:   Mon, 24 Jun 2019 21:32:48 +0800
From:   Zhiqiang Liu <liuzhiqiang26@...wei.com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     <corbet@....net>, <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>, <akpm@...ux-foundation.org>,
        <manfred@...orfullife.com>, <jwilk@...lk.net>,
        <dvyukov@...gle.com>, <feng.tang@...el.com>,
        <sunilmut@...rosoft.com>, <quentin.perret@....com>,
        <linux@...mhuis.info>, <alex.popov@...ux.com>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-fsdevel@...r.kernel.org>,
        "wangxiaogang (F)" <wangxiaogang3@...wei.com>,
        "Zhoukang (A)" <zhoukang7@...wei.com>,
        Mingfangsen <mingfangsen@...wei.com>, <tedheadster@...il.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH next] softirq: enable MAX_SOFTIRQ_TIME tuning with sysctl
 max_softirq_time_usecs

On 2019/6/24 17:45, Thomas Gleixner wrote:
> Zhiqiang,
> 
> On Mon, 24 Jun 2019, Zhiqiang Liu wrote:
>> 在 2019/6/24 0:38, Thomas Gleixner 写道:
>>
>> Thanks again for your detailed advice.
>> As your said, the max_softirq_time_usecs setting without explaining the
>> relationship with CONFIG_HZ will give a false sense of controlability. And
>> the time accuracy of jiffies will result in a certain difference between the
>> max_softirq_time_usecs set value and the actual value, which is in one jiffies
>> range.
>>
>> I will add these infomation in the sysctl documentation and changelog in v2 patch.
> 
> Please make the sysctl milliseconds based. That's the closest approximation
> of useful units for this. This still has the same issues as explained
> before but it's not off by 3 orders of magitude anymore.
> 
> Thanks,
> 
> 	tglx
> 
Thanks for your suggestion.
I will adopt max_softirq_time_ms to replace MAX_SOFTIRQ_TIME in v2.