Sam Dave wrote: > While I write to an LMDB database, while it gets bigger and bigger, I can see > %MEM in top rising steadily. > > This is because %MEM is composed of three things, including "RSfd". From the > top manpage: > > RSfd -- Resident File-Backed Memory Size (KiB) > A subset of resident memory (RES) representing the implicitly shared pages > supporting program images and shared libraries. It also includes explicit file > mappings, both private and shared. > > Is it memory mapping that's resulting in the higher RSfd?
LMDB uses shared memory mapped files, so yes. > > RSfd increases do not seem to have an effect on "buff/cache" or "avail Mem", > i.e. what most people think as "RAM" is not being used up. I still want to > ask, > could too high RSfd use result in less efficient use of memory for other > programs? I'm essentially wondering how efficient common OSes (e.g. MacOS, > Linux) are > in this area. No. The OS can reclaim LMDB's pages (at zero cost) for use by any other program whenever memory demands are tight. > - Sam -- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/
