From: Lai Jiangshan <jiangshanlai@gmail.com>
To: Tejun Heo <tj@kernel.org>
Cc: Yue Hu <zbestahu@gmail.com>,
linux-kernel@vger.kernel.org, huyue2@coolpad.com,
zhangwen@coolpad.com
Subject: Re: [PATCH] workqueue: Drop the NOT_RUNNING check to flags in worker_{set,clr}_flags
Date: Sat, 25 Mar 2023 17:20:14 +0800 [thread overview]
Message-ID: <CAJhGHyAvzjK5r5yfB_wcLPnq=Y=wwsxh=M=EA3x5EsNacRKMVQ@mail.gmail.com> (raw)
In-Reply-To: <ZB0Dwxs6xen7D/qh@slm.duckdns.org>
On Fri, Mar 24, 2023 at 9:58 AM Tejun Heo <tj@kernel.org> wrote:
>
> On Mon, Mar 20, 2023 at 05:26:52PM +0800, Yue Hu wrote:
> > From: Yue Hu <huyue2@coolpad.com>
> >
> > We know whether the worker flags are belong to WORKER_NOT_RUNNING or not
> > when we are setting and clearing them. So check the flags not running
> > related is unnecessary for both the cases.
> >
> > Currently, worker_{set,clr}_flags() are all used for WORKER_NOT_RUNNING
> > except for clearing WORKER_IDLE. Let's change to directly clear it
> > instead. Also, update the comment a little in worker_clr_flags().
>
> I'm not sure this is better. Semantically, the existing code seems clearer
> and less error-prone to me and this isn't gonna make any meaningful perf
> difference. Lai, what do you think?
objdump -DSr kernel/workqueue.o | less
3275: 00 00
3273: R_X86_64_32S current_task
WARN_ON_ONCE(worker->task != current);
3277: 48 39 43 40 cmp %rax,0x40(%rbx)
327b: 0f 85 91 00 00 00 jne 3312 <process_one_work+0x3a2>
!(worker->flags & WORKER_NOT_RUNNING)) {
3281: 8b 43 68 mov 0x68(%rbx),%eax
if ((flags & WORKER_NOT_RUNNING) &&
3284: a9 c8 01 00 00 test $0x1c8,%eax
3289: 75 0b jne 3296 <process_one_work+0x326>
struct worker_pool *pool = worker->pool;
328b: 48 8b 43 48 mov 0x48(%rbx),%rax
pool->nr_running--;
328f: 83 68 20 01 subl $0x1,0x20(%rax)
3293: 8b 43 68 mov 0x68(%rbx),%eax
worker->flags |= flags;
3296: 83 c8 40 or $0x40,%eax
3299: 89 43 68 mov %eax,0x68(%rbx)
It seems the compiler will do the trick. The clearer existing code
seems better.
Thanks
Lai
>
> Thanks.
>
> --
> tejun
next prev parent reply other threads:[~2023-03-25 9:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-20 9:26 [PATCH] workqueue: Drop the NOT_RUNNING check to flags in worker_{set,clr}_flags Yue Hu
2023-03-24 1:58 ` Tejun Heo
2023-03-25 9:20 ` Lai Jiangshan [this message]
2023-03-27 3:07 ` Yue Hu
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