linux-kernel - Re: [PATCH] workqueue: introduce queue_work_cpumask to queue work onto a given cpumask

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Message-ID: <CAEQmJ=gy=ORK9hnxLYL9x_bbJTVozvtpiCfMexROTmYH7ctTBA@mail.gmail.com>
Date:   Fri, 9 Jun 2023 14:23:23 +0800
From:   Yuanhan Zhang <zyhtheonly@...il.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     jiangshanlai@...il.com, linux-kernel@...r.kernel.org,
        pmladek@...e.com, zyhtheonly@...h.net, zwp10758@...il.com,
        tiozhang@...iglobal.com, fuyuanli@...iglobal.com
Subject: Re: [PATCH] workqueue: introduce queue_work_cpumask to queue work
 onto a given cpumask

// I resend this to put it into the same thread, sorry for the confusion.

> Can you elaborate the intended use cases?

Hi Tejun,

Thanks for your reply! Please let me use myself as an example to explain this.

In my scenario, I have 7 cpus on my machine (actually it is uma, so
queue_work_node
or using UNBOUND do not works for me), and for some unlucky reasons
there are always some irqs running on cpu 0 and cpu 6, since I'm using arm64
with irqs tuning into FIFO threads, those threaded irqs are always running on
cpu 0 and 6 too (for affinity). And this would not be fixed easily in
short terms :(

So in order to help async init for better boot times for my devices,
I'd like to prevent
works from running on cpu 0 and 6. With queue_work_cpumask(), it would be simply
done by:

...
cpumask_clear_cpu(0, cpumask);  // actually I use sysfs to parse my cpumask
cpumask_clear_cpu(6, cpumask);
queue_work_cpumask(cpumask, my_wq, &my_work->work);
...


> The code seems duplicated too. Could you do a little refactoring and make
> they (queue_work_cpumask() & queue_work_node()) share some code?

Hi Lai,

Thanks for your advice!

I do the refactoring in PATCH v2, there are some changes:
1. removed WARN_ONCE in previous code
  1). queue_work_node works well in UNBOUND since we have unbound_pwq_by_node()
       in __queue_work() to choose the right node.
  2). queue_work_cpumask does not work in UNBOUND since list
numa_pwq_tbl is designed
       to be per numa node. I comment on this in this patch.
2. remove the previous workqueue_select_cpu_near and let queue_work_node() use
    queue_work_on() and queue_work_cpumask().

I test this patch with 100,000 queue_work_cpumask() &
queue_work_node() with randomly
inputs cpumask & node, it works as expected on my machines (80 cores
x86_64 & 7 cores ARM64
& 16 cores ARM64).

Please help review, thanks a lot!

Thanks,
Tio Zhang


Yuanhan Zhang <zyhtheonly@...il.com> 于2023年6月9日周五 14:07写道：
>
> // I resend this to put it into the same thread, sorry for the confusion.
>
> > Can you elaborate the intended use cases?
>
> Hi Tejun,
>
> Thanks for your reply! Please let me use myself as an example to explain this.
>
> In my scenario, I have 7 cpus on my machine (actually it is uma, so queue_work_node
> or using UNBOUND do not works for me), and for some unlucky reasons
> there are always some irqs running on cpu 0 and cpu 6, since I'm using arm64
> with irqs tuning into FIFO threads, those threaded irqs are always running on
> cpu 0 and 6 too (for affinity). And this would not be fixed easily in short terms :(
>
> So in order to help async init for better boot times for my devices, I'd like to prevent
> works from running on cpu 0 and 6. With queue_work_cpumask(), it would be simply
> done by:
>
> ...
> cpumask_clear_cpu(0, cpumask);  // actually I use sysfs to parse my cpumask
> cpumask_clear_cpu(6, cpumask);
> queue_work_cpumask(cpumask, my_wq, &my_work->work);
> ...
>
>
> > The code seems duplicated too. Could you do a little refactoring and make
> > they (queue_work_cpumask() & queue_work_node()) share some code?
>
> Hi Lai,
>
> Thanks for your advice!
>
> I do the refactoring in PATCH v2, there are some changes:
> 1. removed WARN_ONCE in previous code
>   1). queue_work_node works well in UNBOUND since we have unbound_pwq_by_node()
>        in __queue_work() to choose the right node.
>   2). queue_work_cpumask does not work in UNBOUND since list numa_pwq_tbl is designed
>        to be per numa node. I comment on this in this patch.
> 2. remove the previous workqueue_select_cpu_near and let queue_work_node() use
>     queue_work_on() and queue_work_cpumask().
>
> I test this patch with 100,000 queue_work_cpumask() & queue_work_node() with randomly
> inputs cpumask & node, it works as expected on my machines (80 cores x86_64 & 7 cores ARM64
> & 16 cores ARM64).
>
> Please help review, thanks a lot!
>
> Thanks,
> Tio Zhang