linux-kernel - Re: [RFC PATCH v2 0/3] Move usages of struct __call_single_data to call_single_data

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Date:   Wed, 30 Aug 2023 19:29:40 -0300
From:   Leonardo Brás <leobras@...hat.com>
To:     Chengming Zhou <chengming.zhou@...ux.dev>,
        Jens Axboe <axboe@...nel.dk>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Guo Ren <guoren@...nel.org>,
        Valentin Schneider <vschneid@...hat.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Juergen Gross <jgross@...e.com>,
        Yury Norov <yury.norov@...il.com>,
        Marcelo Tosatti <mtosatti@...hat.com>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 0/3] Move usages of struct __call_single_data to
 call_single_data_t

On Tue, 2023-08-29 at 10:29 +0800, Chengming Zhou wrote:
> On 2023/8/29 08:55, Leonardo Brás wrote:
> > On Tue, 2023-07-04 at 04:22 -0300, Leonardo Brás wrote:
> > > On Tue, 2023-06-13 at 00:51 -0300, Leonardo Bras Soares Passos wrote:
> > > > Friendly ping
> > > > 
> > > > On Sat, May 20, 2023 at 2:30 AM Leonardo Bras <leobras@...hat.com> wrote:
> > > > > 
> > > > > Changes since RFCv1:
> > > > > - request->csd moved to the middle of the struct, without size impact
> > > > > - type change happens in a different patch (thanks Jens Axboe!)
> > > > > - Improved the third patch to also update the .h file.
> > > > > 
> > > > > Leonardo Bras (3):
> > > > >   blk-mq: Move csd inside struct request so it's 32-byte aligned
> > > > >   blk-mq: Change request->csd type to call_single_data_t
> > > > >   smp: Change signatures to use call_single_data_t
> > > > > 
> > > > >  include/linux/blk-mq.h | 10 +++++-----
> > > > >  include/linux/smp.h    |  2 +-
> > > > >  kernel/smp.c           |  4 ++--
> > > > >  kernel/up.c            |  2 +-
> > > > >  4 files changed, 9 insertions(+), 9 deletions(-)
> > > > > 
> > > > > --
> > > > > 2.40.1
> > > > > 
> > > 
> > > Hello Jens,
> > > 
> > > I still want your feedback on this series :)
> > > 
> > > I think I addressed every issue of RFCv1, but if you have any other feedback,
> > > please let me know.
> > > 
> > > Thanks!
> > > Leo
> > 
> > Hello Jens Axboe,
> > 
> > Please provide feedback on this series!
> > 
> > Are you ok with those changes?
> > What's your opinion on them? 
> > 
> > Thanks!
> > Leo
> > 
> 
> Hello,
> 
> FYI, there is no csd in struct request anymore in block/for-next branch,
> which is deleted by this commit:
> 
> commit 660e802c76c89e871c29cd3174c07c8d23e39c35
> Author: Chengming Zhou <zhouchengming@...edance.com>
> Date:   Mon Jul 17 12:00:55 2023 +0800
> 
>     blk-mq: use percpu csd to remote complete instead of per-rq csd
> 
>     If request need to be completed remotely, we insert it into percpu llist,
>     and smp_call_function_single_async() if llist is empty previously.
> 
>     We don't need to use per-rq csd, percpu csd is enough. And the size of
>     struct request is decreased by 24 bytes.
> 
>     This way is cleaner, and looks correct, given block softirq is guaranteed
>     to be scheduled to consume the list if one new request is added to this
>     percpu list, either smp_call_function_single_async() returns -EBUSY or 0.
> 
>     Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
>     Reviewed-by: Ming Lei <ming.lei@...hat.com>
>     Reviewed-by: Christoph Hellwig <hch@....de>
>     Link: https://lore.kernel.org/r/20230717040058.3993930-2-chengming.zhou@linux.dev
>     Signed-off-by: Jens Axboe <axboe@...nel.dk>
> 


Oh, thanks for the heads-up!
I will send reviewed version of patch 3.

I suppose it can go on top of block/for-next, since the above patch is there.
Does that work for you Jens Axboe?

Thanks!
Leo