linux-kernel - Re: [PATCH v1 11/17] lib: add light-weight queuing mechanism.

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Message-ID: <DB109932-C918-4F1E-BAF2-92D921238D54@oracle.com>
Date:   Thu, 14 Sep 2023 14:05:04 +0000
From:   Chuck Lever III <chuck.lever@...cle.com>
To:     Neil Brown <neilb@...e.de>
CC:     Chuck Lever <cel@...nel.org>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        Liam Howlett <liam.howlett@...cle.com>,
        Kees Cook <keescook@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Gow <davidgow@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v1 11/17] lib: add light-weight queuing mechanism.



> On Sep 11, 2023, at 9:30 PM, Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> On Tue, 12 Sep 2023 09:19:59 +1000 "NeilBrown" <neilb@...e.de> wrote:
> 
>> Plain old list_heads (which the code currently uses) require a spinlock
>> to be taken to insert something into the queue.  As this is usually in
>> bh context, it needs to be a spin_lock_bh().  My understanding is that
>> the real-time developers don't much like us disabling bh.  It isn't an
>> enormous win switching from a list_head list to a llist_node list, but
>> there are small gains such as object size reduction and less locking.  I
>> particularly wanted an easy-to-use library facility that could be
>> plugged in to two different uses cases in the sunrpc code and there
>> didn't seem to be one.  I could have written one using list_head, but
>> llist seemed a better fix.  I think the code in sunrpc that uses this
>> lwq looks a lot neater after the conversion.
> 
> Thanks.  Could we please get words such as these into the changelog,
> describing why it was felt necessary to add more library code?
> 
> And also into the .c file, to help people who are looking at it and
> wondering "can I use this".  And to help reviewers who are wondering
> "could they have used Neil's thing".

Neil, are you planning to send along a replacement for 11/17,
or would you like me to fold the above into the patch description
I have now?


--
Chuck Lever