Efficient Insertions in Mnesia tables

Olivier BOUDEVILLE olivier.boudeville@REDACTED
Fri Nov 5 11:15:37 CET 2010


We are trying to write (with mnesia:dirty_write) in a disc_only_copies 
Mnesia table (type: set, not fragmented, not replicated) records (ex: 60 
000 of them) and we observe that the insertion time is increasing as the 
table is increasingly crowded. This is not really a surprise but something 
we need to avoid. What we would like is to have constant (and preferably 
low) insertion times, like we had when writing directly to a file.

We tried to get as close as possible with the following settings and use:

                        % We want tables to be dumped less frequently from 
memory to disc,
                        % in order to buffer writings (default value is 
                        ok = application:set_env( mnesia, dc_dump_limit, 1 

                        % Increases a lot (default value is 100) the 
maximum number of
                        % writes to the transaction log before a new dump 
is performed:
                        ok = application:set_env( mnesia, 
dump_log_write_threshold, 50000 ),

Over time we see the CPU load decrease steadily, the computer seems to 
spend most of its time fighting for locks.

We happen to be in a pretty favorable situation (only writes, no 
concurrent access to a given table). We chose disc_only_copies as there 
might be a large number of such tables and if they filled over time they 
could exhaust the RAM.

Is there anything we missed that would allow us (roughly) constant 
insertion times with Mnesia?

Thanks in advance for any hint,
Best regards,

Olivier Boudeville

EDF R&D : 1, avenue du Général de Gaulle, 92140 Clamart, France
Département SINETICS, groupe ASICS (I2A), bureau B-226
Office : +33 1 47 65 59 58 / Mobile : +33 6 16 83 37 22 / Fax : +33 1 47 
65 27 13

Ce message et toutes les pièces jointes (ci-après le 'Message') sont établis à l'intention exclusive des destinataires et les informations qui y figurent sont strictement confidentielles. Toute utilisation de ce Message non conforme à sa destination, toute diffusion ou toute publication totale ou partielle, est interdite sauf autorisation expresse.

Si vous n'êtes pas le destinataire de ce Message, il vous est interdit de le copier, de le faire suivre, de le divulguer ou d'en utiliser tout ou partie. Si vous avez reçu ce Message par erreur, merci de le supprimer de votre système, ainsi que toutes ses copies, et de n'en garder aucune trace sur quelque support que ce soit. Nous vous remercions également d'en avertir immédiatement l'expéditeur par retour du message.

Il est impossible de garantir que les communications par messagerie électronique arrivent en temps utile, sont sécurisées ou dénuées de toute erreur ou virus.

This message and any attachments (the 'Message') are intended solely for the addressees. The information contained in this Message is confidential. Any use of information contained in this Message not in accord with its purpose, any dissemination or disclosure, either whole or partial, is prohibited except formal approval.

If you are not the addressee, you may not copy, forward, disclose or use any part of it. If you have received this message in error, please delete it and all copies from your system and notify the sender immediately by return message.

E-mail communication cannot be guaranteed to be timely secure, error or virus-free.

More information about the erlang-questions mailing list