From: 914059751@qq.com (胡杨树)
To: linux-arm-kernel@lists.infradead.org
Subject: Query about loops_per_jiffy
Date: Tue, 19 Jan 2010 21:38:26 +0800 [thread overview]
Message-ID: <tencent_2543180B1828B0D317DCD9FC@qq.com> (raw)
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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next reply other threads:[~2010-01-19 13:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-19 13:38 胡杨树 [this message]
2010-01-22 1:11 ` 答复: Query about loops_per_jiffy rocky
-- strict thread matches above, loose matches on Subject: below --
2010-01-19 7:42 胡杨树
2010-01-19 8:21 ` Alessandro Rubini
2010-01-19 8:22 ` Russell King - ARM Linux
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