A couple of month ago, I noticed that I was having a constant stream of disk write of about 1MB\/s on my MacBook (as seen in Activity Monitor.app). That would eventually drain my battery faster when running unplugged.<\/p>\n
First thing to do was to identify the culprit, the process, that generate those writes.<\/p>\n
As I'm not familiar with the BSD sub-system internals, I Googled and found a list of DTrace one-liners that proved to be handy:<\/p>\n
–\u00a0http:\/\/www.brendangregg.com\/DTrace\/dtrace_oneliners.txt<\/a><\/a><\/p>\n The first one:<\/p>\n It shows you the names of the process doing I\/O operations.<\/p>\n From the result I immediatly spotted a process from Postgresql that was generating a fair amount of I\/O while no queries\/vacuum where running.<\/p>\n Now, I know the source might be in Postgresql, but what was happenning? what files were concerned by theses I\/O?<\/p>\n I needed to know what files where opened, so this DTrace gave me the next answer :<\/p>\n This one prints the name of the files being opened by the running processes :<\/p>\n From this output, I found that it would be related to the pg_stat mecanism.<\/p>\n I edited the `postgresql.conf' file and disabled the stat collection by setting:<\/p>\n Then, after restarting postgresql, the continuous flow of writes was gone.<\/p>\n Thank you DTrace!<\/p>\n","protected":false},"excerpt":{"rendered":" A couple of month ago, I noticed that I was having a constant stream of disk write of about 1MB\/s on my MacBook (as seen in Activity Monitor.app). That would eventually drain my battery faster when running unplugged. First thing … Continuer la lecture # dtrace -n 'io:::start { printf(\"%d %s %d\",pid,execname,args[0]->b_bcount); }'<\/pre>\n#\u00a0dtrace -n 'syscall::open*:entry { printf(\"%s %s\", execname, copyinstr(arg0) ); }'<\/pre>\n\u00a0\u00a00 \u00a018514 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0open_nocancel:entry postgres global\/pg_database\n\u00a0\u00a00 \u00a018514 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0open_nocancel:entry postgres pg_stat_tmp\/pgstat.stat\n\u00a0\u00a00 \u00a018514 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0open_nocancel:entry postgres pg_stat_tmp\/pgstat.stat\n\u00a0\u00a01 \u00a017728 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 open:entry mdworker \/.vol\/234881026\/52307726\/\/Contents\/PkgInfo\n\u00a0\u00a01 \u00a017728 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 open:entry mdworker \/opt\/local\/var\/db\/postgresql84\/defaultdb\/pg_stat_tmp\/pgstat.stat\n\u00a0\u00a01 \u00a017728 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 open:entry mds .\n\u00a0\u00a00 \u00a018514 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0open_nocancel:entry postgres pg_stat_tmp\/pgstat.stat\n\u00a0\u00a00 \u00a018514 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0open_nocancel:entry postgres pg_stat_tmp\/pgstat.stat\n\u00a0\u00a00 \u00a018514 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0open_nocancel:entry postgres pg_stat_tmp\/pgstat.stat\n<\/pre>\n
track_activities = off\ntrack_counts = off\n<\/pre>\n