[Valgrind-users] tool=cachegrind always reports LL misses, even if the cache is bigger than the used memory

[Volker D. <u6...@ti...>]

Hallo,

maybe I misunderstood, but it look like I don't understand 
tool=cachegrind correct (or there is a bug).

I have a software. If it runs, then the task manager tells me that is 
use only 38 MB memory.

Now i used cachegrind like this:
valgrind --tool=cachegrind --LL=2097152,16,64 ./fet-cl 
--inputfile=German-100_and_0.fet  --randomseeds10=10 --randomseeds11=11 
--randomseeds12=12 --randomseeds20=20 --randomseeds21=21 
--randomseeds22=22

i got this report:
[...]
==43032== LL misses:           8,283,261  (      7,840,142 rd   +        
443,119 wr)


i doubled the LL cache by this:
valgrind --tool=cachegrind --LL=4194304,16,64 ./fet-cl 
--inputfile=German-100_and_0.fet  --randomseeds10=10 --randomseeds11=11 
--randomseeds12=12 --randomseeds20=20 --randomseeds21=21 
--randomseeds22=22

and got this:
[...]
==48663== LL misses:             230,426  (         89,082 rd   +        
141,344 wr)


That sound ok (larger cache should reduce the misses).

But I continued to double the cache again and again. Up to:
valgrind --tool=cachegrind --LL=268435456,16,64 ./fet-cl 
--inputfile=German-100_and_0.fet  --randomseeds10=10 --randomseeds11=11 
--randomseeds12=12 --randomseeds20=20 --randomseeds21=21 
--randomseeds22=22

So much more memory then my program use at all.
But the misses never drop down to 0. They stay at:
[...]
==6637== LL misses:             180,120  (         41,252 rd   +        
138,868 wr)


I don't understand that. Shouldn't the misses drop down to 0 as soon as 
LL is >64MB (since my software use only 38 MB)? (But i tried up to 256MB 
and it doesn't drop).
Is that a bug in valgrind or is there a bug in my logic in understanding 
the LL misses?

Please let me know.

Thank you!