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From: Arnd Bergmann <arnd@arndb.de>
To: Marc Gonzalez <marc.w.gonzalez@free.fr>
Cc: Matt Wagantall <mattw@codeaurora.org>,
	Mitchel Humpherys <mitchelh@codeaurora.org>,
	Will Deacon <will.deacon@arm.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Bjorn Helgaas <helgaas@kernel.org>,
	Douglas Anderson <dianders@chromium.org>
Subject: Re: [PATCH v1] iopoll: Tweak readx_poll_timeout sleep range
Date: Thu, 13 Jun 2019 14:42:57 +0200	[thread overview]
Message-ID: <CAK8P3a1_WvHYW243MR5-NdFm3cSt+cVGM5EJmOM8uiQMQ3vQjQ@mail.gmail.com> (raw)
In-Reply-To: <c2e6af51-5676-3715-6666-c3f18df7b992@free.fr>

On Thu, Jun 13, 2019 at 2:16 PM Marc Gonzalez <marc.w.gonzalez@free.fr> wrote:
>
> Chopping max delay in 4 seems excessive. Let's just cut it in half.
>
> Signed-off-by: Marc Gonzalez <marc.w.gonzalez@free.fr>
> ---
> When max_us=100, old_min was 26 us; new_min would be 50 us
> Was there a good reason for the 1/4th?
> Is new_min=0 a problem? (for max=1)

You normally want a large enough range between min and max. I don't
see anything wrong with a factor of four.

> @@ -47,7 +47,7 @@
>                         break; \
>                 } \
>                 if (__sleep_us) \
> -                       usleep_range((__sleep_us >> 2) + 1, __sleep_us); \
> +                       usleep_range(__sleep_us / 2, __sleep_us); \
>         } \

You are also missing the '+1' now, so this breaks with __sleep_us=1.

        Arnd

WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: Marc Gonzalez <marc.w.gonzalez@free.fr>
Cc: Douglas Anderson <dianders@chromium.org>,
	Will Deacon <will.deacon@arm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Matt Wagantall <mattw@codeaurora.org>,
	Bjorn Helgaas <helgaas@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mitchel Humpherys <mitchelh@codeaurora.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v1] iopoll: Tweak readx_poll_timeout sleep range
Date: Thu, 13 Jun 2019 14:42:57 +0200	[thread overview]
Message-ID: <CAK8P3a1_WvHYW243MR5-NdFm3cSt+cVGM5EJmOM8uiQMQ3vQjQ@mail.gmail.com> (raw)
In-Reply-To: <c2e6af51-5676-3715-6666-c3f18df7b992@free.fr>

On Thu, Jun 13, 2019 at 2:16 PM Marc Gonzalez <marc.w.gonzalez@free.fr> wrote:
>
> Chopping max delay in 4 seems excessive. Let's just cut it in half.
>
> Signed-off-by: Marc Gonzalez <marc.w.gonzalez@free.fr>
> ---
> When max_us=100, old_min was 26 us; new_min would be 50 us
> Was there a good reason for the 1/4th?
> Is new_min=0 a problem? (for max=1)

You normally want a large enough range between min and max. I don't
see anything wrong with a factor of four.

> @@ -47,7 +47,7 @@
>                         break; \
>                 } \
>                 if (__sleep_us) \
> -                       usleep_range((__sleep_us >> 2) + 1, __sleep_us); \
> +                       usleep_range(__sleep_us / 2, __sleep_us); \
>         } \

You are also missing the '+1' now, so this breaks with __sleep_us=1.

        Arnd

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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2019-06-13 15:22 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-13 12:16 [PATCH v1] iopoll: Tweak readx_poll_timeout sleep range Marc Gonzalez
2019-06-13 12:16 ` Marc Gonzalez
2019-06-13 12:42 ` Arnd Bergmann [this message]
2019-06-13 12:42   ` Arnd Bergmann
2019-06-13 16:04   ` Marc Gonzalez
2019-06-13 16:04     ` Marc Gonzalez
2019-06-13 16:11     ` Doug Anderson
2019-06-13 16:11       ` Doug Anderson
2019-06-13 16:36       ` Marc Gonzalez
2019-06-13 16:36         ` Marc Gonzalez
2019-06-13 17:10         ` Doug Anderson
2019-06-13 17:10           ` Doug Anderson

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