"blkclr (mach_kernel)" shows up in mac's shark profiler. What does it do?

I am profiling a C program using Mac's Shark which shows that some of CPU time goes to "blkclr" in "mach_kernel". What does this kernel function do? I speculate it is related to memory allocation, but I am not sure. I have googled f开发者_运维知识库or some time, but could not find the answer, either. Does someone know this? Thanks in advance.

Zeroes out a block of memory

http://www.cs.cmu.edu/afs/cs.cmu.edu/project/mach/public/src/mkernel/src/kernel/mips/mips_mem_ops.c