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From: Howard Hinnant (howard.hinnant_at_[hidden])
Date: 2007-08-26 19:17:07

On Aug 26, 2007, at 4:49 PM, Peter Dimov wrote:

> Howard Hinnant:
>> I've been using "sizeof(condition)" as shorthand for "reducing L1
>> cache misses". Your technique of moving the checking to a static map
>> (or unordered_map)<void*, void*> does indeed reduce the
>> sizeof(condition), but does not reduce L1 cache misses.
> map<> is the "debug" variation, there's also a "checked release"
> one. They
> do reduce the L1 cache misses on the only path where these misses
> can be
> measured, the path that does not call wait. Once you call wait, you
> enter a
> blocking kernel call and L1 misses cease to be of importance.

My knowledge is not what it should be in this area.

If there are two threads sharing a processor, and one thread is
accessing M1 amount of memory and the other thread is accessing M2
amount of memory, and M1 + M2 is less than the L1 cache size, isn't
that faster than if both M1 and M2 are less than the L1 cache size but
M1 + M2 is larger than the L1 cache size? I.e. can larger memory use
(or more scattered memory use) on one thread make cache misses more
likely on another thread?


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