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SubjectRe: PATCH 2.3.26: kmalloc GFP_ZERO
On Tue, 9 Nov 1999 yodaiken@chelm.cs.nmt.edu wrote:

>> Are you still talking about a cache of zeroed pages? Looks a bad idea to
>> me.
>
>The numbers say otherwise.

So you are benchmarking a machine that spend time in the idle task.

If you benchmarked a kernel compile make sure to compile with:

make MAKE='make -j4' -j4 bzImage

Then the numbers will agree with me (if you won't hit swap). Also make
sure to apply my SMP scheduler patch in the aa patches.

>The idle task will build a cache of zeroed pages. If nothing is in the
>cache, you pay the standard cost.

You'll also pay the check to see if the pool is empty before doing the
memset by hand. You'll take the slow path in the case worth to optimize.

>> the idle task will be less fast in rescheduling itself.
>
>Why?

Because when you'll enter the memset in the idle task you won't exit it in
the middle even if somebody sent you a reschedule interrupt. The increased
scheduler latency while rescheduling the idle task will be close to the
time of a memset/2 (if the pool was empty).

Andrea


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