stap shows kfree() is 5 times more than kallocs, how could be?

[Lev Olshvang]

Hello all,

I am debugging kernel module and use  SystemTap to monitor requested and freed memory.

I see that SystemTap statistics shows that kfree() is called 5 times more than kalloc. 
It happens not only on my module, it happens on VirtualBox vboxsf driver as well.

See hits count below  kmalloc hits: 21561
                                  kfree      hits: 102175


----- probe hit report:
kernel.function("__kmalloc at mm/slub.c:3706"), (./kmalloc_argus.stp:10:1), hits: 21561, cycles: 21228min/52226avg/334688max, from: kernel.function("__kmalloc at mm/slub.c:3706") from: kernel.function("__kmalloc"), index: 0
kernel.function("__kmalloc at mm/slub.c:3706").return, (./kmalloc_argus.stp:25:1), hits: 21561, cycles: 18843min/51228avg/406816max, from: kernel.function("__kmalloc at mm/slub.c:3706").return from: kernel.function("__kmalloc").return, index: 1
kernel.function("kfree at mm/slub.c:3843"), (./kmalloc_argus.stp:38:1), hits: 102175, cycles: 400min/1557avg/499754max, from: kernel.function("kfree at mm/slub.c:3843") from: kernel.function("kfree"), index: 2


Please comment.

Lev