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Date:   Sun, 29 Mar 2020 19:13:33 +0200
Message-ID: <s5h7dz3ccea.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     George Spelvin <lkml@SDF.ORG>
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
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        <s5ho8sfd2dk.wl-tiwai@suse.de>
        <20200329121129.GC11951@SDF.ORG>
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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:
> > On Thu, 22 Aug 2019 02:25:10 +0200, George Spelvin wrote:
> >> Likewise, "msecs_to_jiffies(seconds * 1000)" is more
> >> conveniently written "seconds * HZ".
> > 
> > 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...


thanks,

Takashi