linux-kernel - Re: [PATCH v3 0/1] multi-threading device shutdown

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Message-ID: <ca8b0bf8-e848-be2a-c9f5-b01ee65551b3@oracle.com>
Date:   Mon, 14 May 2018 12:54:37 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        linux-kernel@...r.kernel.org, jeffrey.t.kirsher@...el.com,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        alexander.duyck@...il.com, tobin@...orbit.com
Subject: Re: [PATCH v3 0/1] multi-threading device shutdown

On 05/14/2018 11:03 AM, Greg KH wrote:
> On Mon, May 07, 2018 at 11:54:01AM -0400, Pavel Tatashin wrote:
>> Changelog
>> v2 - v3
>> 	- Fixed warning from kbuild test.
>> 	- Moved device_lock/device_unlock inside device_shutdown_tree().
>>
>> v1 - v2
>> 	- It turns out we cannot lock more than MAX_LOCK_DEPTH by a single
>> 	  thread. (By default this value is 48), and is used to detect
>> 	  deadlocks. So, I re-wrote the code to only lock one devices per
>> 	  thread instead of pre-locking all devices by the main thread.
>> 	- Addressed comments from Tobin C. Harding.
>> 	- As suggested by Alexander Duyck removed ixgbe changes. It can be
>> 	  done as a separate work scaling RTNL mutex.
>>
>> Do a faster shutdown by calling dev->*->shutdown(dev) in parallel.
>> device_shutdown() calls these functions for every single device but
>> only using one thread.
>>
>> Since, nothing else is running on the machine by the device_shutdown()
>> s called, there is no reason not to utilize all the available CPU
>> resources.
> 
> Ah, we can hope so.  I bet this is going to break something, so can we
> have some way of turning it on/off dynamically for when it does?

Hi Greg,

Sure, I will add a kernel parameter to optionally disable this feature in the next patch revision.

Thank you,
Pavel

> 
> thanks,
> 
> greg k-h
>