From: George Spelvin <lkml@SDF.ORG>
To: Takashi Iwai <tiwai@suse.de>
Cc: linux-kernel@vger.kernel.org, Hannes Reinecke <hare@suse.de>,
linux-scsi@vger.kernel.org,
Marek Lindner <mareklindner@neomailbox.ch>,
Simon Wunderlich <sw@simonwunderlich.de>,
Antonio Quartulli <a@unstable.cc>,
Sven Eckelmann <sven@narfation.org>,
b.a.t.m.a.n@diktynna.open-mesh.org,
Johannes Berg <johannes@sipsolutions.net>,
linux-wireless@vger.kernel.org, Jaroslav Kysela <perex@perex.cz>,
Takashi Iwai <tiwai@suse.com>,
alsa-devel@alsa-project.org, lkml@sdf.org
Subject: Re: [RFC PATCH v1 13/50] Avoid some useless msecs/jiffies conversions
Date: Sun, 29 Mar 2020 17:50:32 +0000 [thread overview]
Message-ID: <20200329175032.GE4675@SDF.ORG> (raw)
In-Reply-To: <s5h7dz3ccea.wl-tiwai@suse.de>
On Sun, Mar 29, 2020 at 07:13:33PM +0200, Takashi Iwai wrote:
> On Sun, 29 Mar 2020 14:11:29 +0200, George Spelvin wrote:
>> On Sun, Mar 29, 2020 at 09:52:23AM +0200, Takashi Iwai wrote:
>>> I thought the compiler already optimizes to the constant calculation
>>> for the above case?
>>
>> It optimizes that if the entire argument, including "seconds", is
>> a compile-time constant.
>>
>> However, given "msecs_to_jiffies(hdev->rpa_timeout * 1000);",
>> the computatin is non-trivial.
>
> Fair enough. But it's still a question whether an open code X * HZ is
> good at all...
I'm sorry, I don't understand what you mean by "good at all" here.
The value computed is exactly the same.
msecs_to_jiffies(x) is basically (x * HZ + 999) / 1000, so
msecs_to_jiffies(s * 1000)
= (s * 1000 * HZ + 999) / 1000
= s * HZ + 999/1000
= s * HZ.
next prev parent reply other threads:[~2020-03-29 17:56 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-22 0:25 [RFC PATCH v1 13/50] Avoid some useless msecs/jiffies conversions George Spelvin
2020-03-29 7:52 ` Takashi Iwai
2020-03-29 12:11 ` George Spelvin
2020-03-29 17:13 ` Takashi Iwai
2020-03-29 17:50 ` George Spelvin [this message]
2020-03-29 18:16 ` James Bottomley
2020-03-29 21:18 ` George Spelvin
2020-03-30 6:27 ` Takashi Iwai
2020-03-30 6:51 ` George Spelvin
2020-03-30 7:29 ` Takashi Iwai
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200329175032.GE4675@SDF.ORG \
--to=lkml@sdf.org \
--cc=a@unstable.cc \
--cc=alsa-devel@alsa-project.org \
--cc=b.a.t.m.a.n@diktynna.open-mesh.org \
--cc=hare@suse.de \
--cc=johannes@sipsolutions.net \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=linux-wireless@vger.kernel.org \
--cc=mareklindner@neomailbox.ch \
--cc=perex@perex.cz \
--cc=sven@narfation.org \
--cc=sw@simonwunderlich.de \
--cc=tiwai@suse.com \
--cc=tiwai@suse.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox