-----Original Message----- From: Allen, Jack [mailto:Jack.Allen@xxxxxxxxxxxx] Sent: Wednesday, February 28, 2007 2:00 PM To: General Red Hat Linux discussion list Subject: RE: Locking shared memory -----Original Message----- From: Mike Kearey [mailto:mkearey@xxxxxxxxxx] Sent: Wednesday, February 28, 2007 12:56 AM To: General Red Hat Linux discussion list Subject: Re: Locking shared memory Allen, Jack wrote: > I do not think the error is because of the first explanation of ENOMEM > So my question is based on the second one. > > Is there a kernel or vm parameter that controls how much memory a > process can utilize? > > I am running RH AS 4.4 32 bit with 2GB of physical memory. > > Thanks in advance: > Jack Allen > G'day Jack, There is memlock limit in shell, changed using the ulimit command from bash. See ulimit -l: $ ulimit -l 32 The actual hard and soft limits are controlled on a Red Hat system using the pam_limits pam module, using the config file /etc/security/limits.conf Check the doc's from RHEL4 for the pam module for details : /usr/share/doc/pam-0.77/txts/README.pam_limits This may well be where the ENOMEM came from, as the default limit that a user may lock memory is 32kB. Cheers, Michael ========================================= Michael: Thanks for the information. Since I do not want all users to have the limit increased for them, I do not want to add and entry in /etc/security/limits.conf. I know it can be done on a per user bases, but any user can start the main database program that creates the shared memory segments. And because the main program runs set UID and the owner of the program is root, it runs as root no matter who starts. I know there are those that think SUID programs to root are dangerous, but we have to have it this way to make things work the way we want it to. It is limited it what it does, in that it does not execute or create files, etc.. arbitrarily, it has very specific things that is does. With that being said what I did was set the resource limit within the program via setrlimit(RLIMIT_MEMLOCK,&rlimit). I set the limit to 1GB and setrlimit returned a success value. But when I try to lock the second 256MB shared memory segment address it still fails the same way. The system has 2GB of memory and there is basically nothing else running on the system other than all the standard/default processes for various services. Do you or anyone else have anymore thoughts as to what may be keeping me from locking the second shared memory segment address? Thank: Jack Allen =================================================== All: Some additional information. As I have said when I try to lock the second shared memory address via mlock(addr,size) it fails. I have been assuming incorrectly that that errno of ENOMEM meant I was hitting a limit. So I decided to try some other things to make sure. Using the same 512MB overall size for the amount of shared memory I allocated it in 32MB segments, which gives me 16 segments. I was able to lock all but the last segment. This would again sound like I had hit a limit. My next test was to use 1024MB overall and use 64MB segments, which give 16 segments also. I was able to lock all but the last segment again. So this means I was able to lock 960MB with no problem. Therefore it does not seem to be limit of the maximum amount I can lock, because the last test exceeded the first test by 704MB. So I suspect errno may be indicating the wrong reason for the failure. I think it has something to do with an address boundary or page alignment. Does anyone have any thoughts. Thanks: Jack Allen -- redhat-list mailing list unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe https://www.redhat.com/mailman/listinfo/redhat-list -- redhat-list mailing list unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe https://www.redhat.com/mailman/listinfo/redhat-list
