- if (FLAGS_drop_log_memory) {
- if (file_length_ >= logging::kPageSize) {
- // don't evict the most recent page
- uint32 len = file_length_ & ~(logging::kPageSize - 1);
- posix_fadvise(fileno(file_), 0, len, POSIX_FADV_DONTNEED);
+ // Only consider files >= 3MiB
+ if (FLAGS_drop_log_memory && file_length_ >= (3 << 20)) {
+ // Don't evict the most recent 1-2MiB so as not to impact a tailer
+ // of the log file and to avoid page rounding issue on linux < 4.7
+ uint32 total_drop_length = (file_length_ & ~((1 << 20) - 1)) - (1 << 20);
+ uint32 this_drop_length = total_drop_length - dropped_mem_length_;
+ if (this_drop_length >= (2 << 20)) {
+ // Only advise when >= 2MiB to drop
+ posix_fadvise(fileno(file_), dropped_mem_length_, this_drop_length,
+ POSIX_FADV_DONTNEED);
+ dropped_mem_length_ = total_drop_length;