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Re: Antw: Re: LMDB database size

Ulrich Windl wrote:
Howard Chu <hyc@symas.com> schrieb am 25.01.2014 um 19:07 in Nachricht
Markus Doppelbauer wrote:
We are using BerkeleyDB since a decade - but we are searching for something
more lightweight. LMDB is what we are looking for ...  ^^
The small code  and the benchmark-results are very impressive!
A question: We have a server with 4 GB RAM. One of the BerkeleyDB-files has
about 20 GB.This particular database is a kind of archive - hardly read and
written (maybe once per minute).
Is it possible to "mmap()" a 20 GB database into the RAM?


If yes, will the server
start "swapping"?


This is only true (AFAIK)

You've already demonstrated multiple times that "as far as you know" is not far at all.

if the applications uses huge pages or memory
locking. In other cases it depends on the OS and the other applications.
In general mmap files "swap" onto themselves, and you would not call it
"swapping" in the usual sense...

Thus, the answer is "No", as I already said, and you have added no value to the discussion.


  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/