From: 914059751@qq.com (rocky)
To: linux-arm-kernel@lists.infradead.org
Subject: 答复: Query about loops_per_jiffy
Date: Fri, 22 Jan 2010 09:11:29 +0800 [thread overview]
Message-ID: <6134FC3AD99C4CA8A47F7E3D5E71C470@dufan> (raw)
In-Reply-To: <tencent_2543180B1828B0D317DCD9FC@qq.com>
Green hand apology for the unintended CC, I should make this query personal.
_____
???: linux-arm-kernel-bounces at lists.infradead.org
[mailto:linux-arm-kernel-bounces at lists.infradead.org] ?? ???
????: 2010?1?19? 21:38
???: Alessandro Rubini
??: linux-arm-kernel
??: Re: Query about loops_per_jiffy
Are you Alessandro Rubini of LINUX DEVICE DRIVER?
------------------ Original ------------------
From: "Alessandro Rubini"<rubini-list@gnudd.com>;
Date: Tue, Jan 19, 2010 04:21 PM
To: "914059751"<914059751@qq.com>;
Cc: "linux-arm-kernel"<linux-arm-kernel@lists.infradead.org>;
Subject: Re: Query about loops_per_jiffy
> (loops_per_jiffy * HZ)/1000,000 will give a BogoMips value.
No, it will give a BogoLips (loops per second). A loop is two instructions,
in ./arch/arm/lib/delay.S (function __delay) called by init/calibrate.c ..
To have bogomips you need to multiply by two.
> then why calibrate_delay do it like the following:
> printk(KERN_CONT "%lu.%02lu BogoMIPS (lpj=%lu)\n",
> loops_per_jiffy/(500000/HZ),
> (loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy);
It's correct, using normal integer aritmetics care.
/alessandro
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2010-01-19 13:38 Query about loops_per_jiffy 胡杨树
2010-01-22 1:11 ` rocky [this message]
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