From: Peter Zijlstra <peterz@infradead.org>
To: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH 1/2] lib: Proportions with flexible period
Date: Thu, 17 May 2012 23:35:12 +0200 [thread overview]
Message-ID: <1337290512.4281.91.camel@twins> (raw)
In-Reply-To: <1337096583-6049-2-git-send-email-jack@suse.cz>
On Tue, 2012-05-15 at 17:43 +0200, Jan Kara wrote:
> + if (numerator > ((long long)denominator) * max_frac / 100)
Does that even compile on 32bit archs?
Operator precedence is *,/ left-to-right, so that's:
long long t1 = (long long)denom * max_frac
long long t2 = t1 / 100;
Which is a 64bit signed division.
There's a reason I used that max_prop_frac thing you removed, it avoids
having to do the division at all and allows a mult and shift instead.
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WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH 1/2] lib: Proportions with flexible period
Date: Thu, 17 May 2012 23:35:12 +0200 [thread overview]
Message-ID: <1337290512.4281.91.camel@twins> (raw)
In-Reply-To: <1337096583-6049-2-git-send-email-jack@suse.cz>
On Tue, 2012-05-15 at 17:43 +0200, Jan Kara wrote:
> + if (numerator > ((long long)denominator) * max_frac / 100)
Does that even compile on 32bit archs?
Operator precedence is *,/ left-to-right, so that's:
long long t1 = (long long)denom * max_frac
long long t2 = t1 / 100;
Which is a 64bit signed division.
There's a reason I used that max_prop_frac thing you removed, it avoids
having to do the division at all and allows a mult and shift instead.
next prev parent reply other threads:[~2012-05-17 21:35 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-15 15:43 [PATCH 0/2 v3] Flexible proportions Jan Kara
2012-05-15 15:43 ` Jan Kara
2012-05-15 15:43 ` [PATCH 1/2] lib: Proportions with flexible period Jan Kara
2012-05-15 15:43 ` Jan Kara
2012-05-17 21:35 ` Peter Zijlstra [this message]
2012-05-17 21:35 ` Peter Zijlstra
2012-05-18 14:33 ` Jan Kara
2012-05-18 14:33 ` Jan Kara
2012-05-17 21:56 ` Peter Zijlstra
2012-05-17 21:56 ` Peter Zijlstra
2012-05-18 14:42 ` Jan Kara
2012-05-18 14:42 ` Jan Kara
2012-05-18 10:43 ` Peter Zijlstra
2012-05-18 10:43 ` Peter Zijlstra
2012-05-18 14:45 ` Jan Kara
2012-05-18 14:45 ` Jan Kara
2012-05-15 15:43 ` [PATCH 2/2] block: Convert BDI proportion calculations to flexible proportions Jan Kara
2012-05-15 15:43 ` Jan Kara
2012-05-17 22:04 ` Peter Zijlstra
2012-05-17 22:04 ` Peter Zijlstra
2012-05-18 14:24 ` Jan Kara
2012-05-18 14:24 ` Jan Kara
2012-05-18 14:34 ` Peter Zijlstra
2012-05-18 14:34 ` Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2012-05-24 16:59 [PATCH 0/2 v4] Flexible proportions Jan Kara
2012-05-24 16:59 ` [PATCH 1/2] lib: Proportions with flexible period Jan Kara
2012-05-24 16:59 ` Jan Kara
2012-05-03 22:39 [PATCH 0/2 v2] Flexible proportions for BDIs Jan Kara
2012-05-03 22:39 ` [PATCH 1/2] lib: Proportions with flexible period Jan Kara
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