[0/3] selftests/mm: mremap_test: Optimizations and style fixes

Message

Dev Jain March 30, 2024, 5:35 p.m. UTC

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(-)