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Message-Id: <f8de460d3c5489f3b1ec407e5d8d8c0b@kernel.crashing.org> Date: Wed, 3 Jan 2007 19:33:52 +0100 From: Segher Boessenkool <segher@...nel.crashing.org> To: Dave Jones <davej@...hat.com> Cc: Linux Kernel <linux-kernel@...r.kernel.org>, mingo@...hat.com Subject: Re: inaccurate migration cost calculation? > Across different boots using the same 2.6.19 kernel on a quad-core xeon > I see huge variance in the migration_cost being reported during boot. > > -migration_cost=39,3940 > +migration_cost=25,4941 > > This CPU has a very large cache which could be key here... > L1 Instruction cache: 32KB, 8-way associative. 64 byte line size. > L1 Data cache: 32KB, 8-way associative. 64 byte line size. > L3 unified cache: 4MB, 16-way associative. 64 byte line size. That last cache is shared between CPU cores, which leads to big non-determinism -- not sure if there's much you can do about it. Segher - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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