The mremap_test, in a worst case controlled by the -t flag, does a for loop iteration in orders of GB. Without compromising on the stdout report, the aim is to reduce this time.
A pre-filled random buffer is allocated based on the seed, replacing repetitive rand() calls. The byte pattern in the memory locations is set through memcpy() from the random buffer.
Replacing the loop for printing the mismatch index to stdout, employ an efficient algorithm by breaking the comparison into chunks, use the highly optimized memcmp() library function, and when a mismatch does occur, only then do a brute force iteration.
Also, use sscanf() to parse /proc/self/maps for consistency across files.
Execution time results (x86 system): ./mremap_test Original: 3 seconds After change: 0.8 seconds
./mremap_test -t100 Original: 17 seconds After change: 2 seconds
./mremap_test -t0 (worst case): Original: 9:40 minutes After change: 45 seconds
Dev Jain (3): selftests/mm: mremap_test: Optimize using pre-filled random array and memcpy selftests/mm: mremap_test: Optimize execution time from minutes to seconds using chunkwise memcmp selftests/mm: mremap_test: Use sscanf to parse /proc/self/maps
tools/testing/selftests/mm/mremap_test.c | 204 +++++++++++++++++------ 1 file changed, 153 insertions(+), 51 deletions(-)