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Date: Thu, 29 Feb 2024 17:01:43 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
To: David Laight <David.Laight@ACULAB.COM>,
        "'Thorsten Blum'" <thorsten.blum@toblux.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
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        Dave Hansen <dave.hansen@linux.intel.com>,
        "x86@kernel.org" <x86@kernel.org>
CC: "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Wei Liu <wei.liu@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] x86/apic: Use div64_ul() instead of do_div()
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>>=20
>> Change deltapm to unsigned long and replace do_div() with div64_ul()
>> which doesn't implicitly cast the divisor and doesn't unnecessarily
>> calculate the remainder=2E
>
>Eh? they are entirely different beasts=2E
>
>do_div() does a 64 by 32 divide that gives a 32bit quotient=2E
>div64_ul() does a much more expensive 64 by 64 divide that
>can generate a 64bit quotient=2E
>
>The remainder is pretty much free in both cases=2E
>If a cpu has a divide instruction it will almost certainly
>put the result in one register and the quotient in another=2E
>

Not on e=2Eg=2E RISC-V=2E