Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20200213141823.2174236-1-mplaneta@os.inf.tu-dresden.de>
 <20200213153645.GA11313@redhat.com> <82715589-8b59-5cfd-a32f-1e57871327fe@os.inf.tu-dresden.de>
In-Reply-To: <82715589-8b59-5cfd-a32f-1e57871327fe@os.inf.tu-dresden.de>
From:   Song Liu <song@kernel.org>
Date:   Thu, 13 Feb 2020 15:42:45 -0800
Message-ID: <CAPhsuW70_HtmxA0qmUVLk4L+Ls5t=0j0k5D4fbT4fNY59L2UpQ@mail.gmail.com>
Subject: Re: Remove WQ_CPU_INTENSIVE flag from unbound wq's
To:     Maksym Planeta <mplaneta@os.inf.tu-dresden.de>
Cc:     Mike Snitzer <snitzer@redhat.com>,
        Zhou Wang <wangzhou1@hisilicon.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Alasdair Kergon <agk@redhat.com>, dm-devel@redhat.com,
        Gao Xiang <xiang@kernel.org>, Chao Yu <chao@kernel.org>,
        linux-crypto@vger.kernel.org,
        open list <linux-kernel@vger.kernel.org>,
        linux-raid <linux-raid@vger.kernel.org>,
        linux-erofs@lists.ozlabs.org
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Feb 13, 2020 at 8:19 AM Maksym Planeta
<mplaneta@os.inf.tu-dresden.de> wrote:
>
>
>
> On 13/02/2020 16:36, Mike Snitzer wrote:
> > On Thu, Feb 13 2020 at  9:18am -0500,
> > Maksym Planeta <mplaneta@os.inf.tu-dresden.de> wrote:
> >
> >> The documentation [1] says that WQ_CPU_INTENSIVE is "meaningless" for
> >> unbound wq. I remove this flag from places where unbound queue is
> >> allocated. This is supposed to improve code readability.
> >>
> >> 1. https://www.kernel.org/doc/html/latest/core-api/workqueue.html#flags
> >>
> >> Signed-off-by: Maksym Planeta <mplaneta@os.inf.tu-dresden.de>
> >
> > What the Documentation says aside, have you cross referenced with the
> > code?  And/or have you done benchmarks to verify no changes?
> >
>
> It seems so from the code. Although, I'm not 100% confident. I did not
> run benchmarks, instead I relied that on the assumption that
> documentation is correct.

From the code, WQ_CPU_INTENSIVE is only used to set
WORKER_CPU_INTENSIVE, and WORKER_CPU_INTENSIVE is only used
as part of WORKER_NOT_RUNNING, which includes WORKER_UNBOUND.
So, I agree that with current code, WQ_CPU_INTENSIVE with WQ_UNBOUND
is same as WQ_UNBOUND alone.

However, I don't think it is necessary to make the changes. They don't really
improve readability of the code.

Thanks,
Song