I can trigger latencies up to ~1.1 ms with a CVS checkout. It looks like inside ext3_try_to_allocate_with_rsv, we spend a long time in this loop:
ext3_test_allocatable (bitmap_search_next_usable_block) find_next_zero_bit (bitmap_search_next_usable_block) find_next_zero_bit (bitmap_search_next_usable_block) ext3_test_allocatable (bitmap_search_next_usable_block) find_next_zero_bit (bitmap_search_next_usable_block) find_next_zero_bit (bitmap_search_next_usable_block) etc. Lee
ext3_reservation.bz2
Description: application/bzip