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Entry  15 Jul 2015, Konstantin Olchanski, Info, mlogger improvements 
    Reply  23 Jul 2015, Konstantin Olchanski, Info, rootana lz4 support, mlogger improvements 
    Reply  23 Jul 2015, Konstantin Olchanski, Info, mlogger improvements 
    Reply  29 Jul 2015, Konstantin Olchanski, Info, mlogger improvements - CRC32C, SHA-2 
Message ID: 1068     Entry time: 15 Jul 2015     Reply to this: 1075   1076   1085
Author: Konstantin Olchanski 
Topic: Info 
Subject: mlogger improvements 
A set of improvements to mlogger is in:

a) event buffer (SYSTEM) size up to 2GB
b) test version of LZ4 high speed compression, support for bzip2 and pbzip2


a) previously contents of shared memory buffers (SYSTEM, SYSMSG, etc) were periodically saved to disk 
files SYSTEM.SHM, SYSMSG.SHM, etc. This was not workable for large event buffers - reading/writing 2GB 
of data takes quite some time. We have decided that saving buffer contents to disk is no longer necessary 
and ss_shm_close() no longer writes SYSTEM.SHM, SYSMSG.SHM, etc. From now on you will still see these 
files created, but size will be 0. The file ODB.SHM is not affected by this - ODB contents is saved to 
ODB.SHM via ss_shm_flush().

b) as a rework of mlogger file output drivers (using chainable c++ classes), test versions of new 
compression algorithms have been added. In the present test version, they are controlled by the value of 

The plan is to ultimately have following outputs from the mlogger:

- ROOT output - save as before, but you have to use rmlogger executable
- FTP output - for high speed write over the network
- .mid output for uncompressed data
- .mid.gz - gzip1 compressed data - best compromise between compression ratio and speed - will be the 
new default
- .mid.bz2 via pbzip2 (parallel bzip2) - maximum compression ratio
- .mid.lz4 - lz4 compression for high speed data taking - maximum compression speed

The current test version implements the following selections of "compression":

80 - ROOT output through the new driver (use rmlogger executable)
98 - null output (no file written)
99 - uncompressed disk output
100 - lz4 comression
200 - piped bzip2 compression
201 - piped pbzip2 compression
300 - gzip compression
301 - gzip1 compression
309 - gzip9 compression

in addition the old selections are still available:
0 - uncompressed output
1 - gzip1 compression
9 - gzip9 compression

The final implementation will include a better way to configure the mlogger output channels.

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