Messages in this thread | | | Date | Wed, 16 Feb 2000 20:37:22 +0100 | From | François Désarménien <> | Subject | /proc/PID/cmdline empty, although process is not swapped out |
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Hello again,
Maybe I'm missing something, so I ask you.
Oracle (again) background processes all come from a single binary called $ORACLE_HOME/bin/oracle, but they are exec'ed with different names, such as 'ora_pmon_SID' where pmon means 'process monitor' and 'SID' is the session ID.
Every background processes are awaked by a SIGALRM every few seconds to check if something has to be done. For example, the pmon process awakes every 3 seconds: doing a 'ptrace -p PID' shows:
semop(0x300, 0x1, 0, 0xbfffeb5c) = -1 EINTR (Interrupted system call) --- SIGALRM (Alarm clock) --- rt_sigprocmask(SIG_BLOCK, [], NULL, 8) = 0 gettimeofday({950728786, 770759}, NULL) = 0 rt_sigprocmask(SIG_UNBLOCK, [], NULL, 8) = 0 rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, [ALRM], NULL, 8) = 0 gettimeofday({950728786, 771556}, NULL) = 0 setitimer(ITIMER_REAL, {it_interval={0, 0}, it_value={3, 0}}, NULL) = 0 rt_sigprocmask(SIG_UNBLOCK, [ALRM], NULL, 8) = 0
repeating every 3 seconds until cancel.
When I do a 'ps ax', the process is usually shown fully qualified, as I understand coming from '/proc/PID/cmdline', but sometimes, it is shown as [oracle] , /proc/PID/cmdline returning nothing, so the executable name is taken (as I understand) from /proc/PID/stat.
Reading the 'proc.txt' documentation, I understood that it is the case when processes are swapped out to disk, but clearly, those *shouldn't, as they are quite often running (maybe not from a scheduler point of view ?).
This is quite annoying, because the *only* way to know if an instance is running from a script point of view is to grep ora_pmon_A from ps ax output.
It seems to me (and to Oracle support) that the output of 'ps ax' and therefore /proc filesystem is not really normal.
I'm running a 2.2.13 plain kernel, compiled with gcc 2.7.2, no SMP support.
Could someone enlighten me ? I've red as much kernel documentation as I found, but found nothing that could help on this topic.
François
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