From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: William Breathitt Gray <vilhelm.gray@gmail.com>
Cc: Lukas Wunner <lukas@wunner.de>,
Syed Nayyar Waris <syednwaris@gmail.com>,
akpm@linux-foundation.org, arnd@arndb.de,
Linus Walleij <linus.walleij@linaro.org>,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/6] bitops: Introduce the the for_each_set_clump macro
Date: Fri, 24 Apr 2020 19:34:10 +0300 [thread overview]
Message-ID: <20200424163410.GD185537@smile.fi.intel.com> (raw)
In-Reply-To: <20200424150828.GA5034@icarus>
On Fri, Apr 24, 2020 at 11:09:26AM -0400, William Breathitt Gray wrote:
> On Fri, Apr 24, 2020 at 05:00:58PM +0200, Lukas Wunner wrote:
> > On Fri, Apr 24, 2020 at 08:22:38PM +0530, Syed Nayyar Waris wrote:
> > > On Fri, Apr 24, 2020 at 7:40 PM Lukas Wunner <lukas@wunner.de> wrote:
> > > > On Fri, Apr 24, 2020 at 05:55:21PM +0530, Syed Nayyar Waris wrote:
...
> > > So, this function preserves the behaviour of earlier
> > > bitmap_set_value8() function and also adds extra functionality to
> > > that.
> >
> > Please leave drivers as is which use exclusively 8-bit accesses,
> > e.g. gpio-max3191x.c and gpio-74x164.c. I'm fearing a performance
> > regression if your new generic variant is used. They work perfectly
> > fine the way they are and I don't see any benefit this series may have
> > for them.
> >
> > If there are other drivers which benefit from the flexibility of your
> > generic variant then I'm not opposed to changing those.
> We can leave of course bitmap_set_value8 alone, but for 8-bit values the
> difference in latency I suspect is primarily due to the conditional test
> for the word boundaries. This latency is surely overshadowed by the I/O
> latency of the GPIO drivers, so I don't think there's much harm in
> changing those to use the generic function when the bottleneck will not
> be due to the bitmap_set_value/bitmap_get_value operations.
Okay, how many new (non-8-bit) users this will target?
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2020-04-24 16:34 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-24 12:25 [PATCH 1/6] bitops: Introduce the the for_each_set_clump macro Syed Nayyar Waris
2020-04-24 14:10 ` Lukas Wunner
2020-04-24 14:52 ` Syed Nayyar Waris
2020-04-24 15:00 ` Lukas Wunner
2020-04-24 15:09 ` William Breathitt Gray
2020-04-24 16:34 ` Andy Shevchenko [this message]
2020-04-24 16:42 ` William Breathitt Gray
2020-04-24 17:59 ` Lukas Wunner
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