https://bugs.openldap.org/show_bug.cgi?id=9475
--- Comment #2 from leslie <[email protected]> --- Read the entire file before running can be as fast as MAP_POPULATE. But I think using MAP_POPULATE is better, by providing a 'map_populate' parameter in 'env_new' function, users can clearly know this feature. <[email protected]> 于2021年2月22日周一 下午9:59写道： > https://bugs.openldap.org/show_bug.cgi?id=9475 > > --- Comment #1 from Howard Chu <[email protected]> --- > (In reply to leslie from comment #0) > > In some case (such as cloud computing platforms), the reading speed of > large > > files is very fast while the small files is very slow, and we have enough > > memory, so we hope to prefetch the entire LMDB file into the memory > during > > MMAP through the MAP_POPULATE flag . According to our test, this is > faster > > than using readahead flag. Here are some test data: > > > > # mmap with no readahead > > read one sample: 0.2s > > total time: 4800s > > > > > > # mmap with readahead > > read one sample: 0.0001s~0.03s > > total time: 95.86s > > > > # mmap with MAP_POPULATE > > db init: 20s > > read one sample: 0.0001s > > total time: 78s > > Have you tested the performance by simply dd'ing the entire file into > memory > before running your test? `dd if=data.mdb of=/dev/null` would be > sufficient to > preload the data into memory. > > -- > You are receiving this mail because: > You reported the issue. -- You are receiving this mail because: You are on the CC list for the issue.
