I'm sure this is a FAQ somewhere, but I can't find it on my system right off hand. So...
Christian Hammers <[EMAIL PROTECTED]> writes: CH> I have a serious problem. One of the servers I administrate seems to CH> have a buffer leak. free and vmstat show me that the buffer size CH> increases by some K every second leading to a 15M memory loss per hour. CH> I'm currently running a PII with 256M RAM and kernel 2.2.15 CH> (latest). Yup, that sounds about right. Except that it's not a problem. So memory in your system can be used for one of a few things. The kernel might be using it directly; there's probably about a meg missing from your 'free' total line for this. You can minimize this by reducing the number of modules you have loaded and the amount of stuff you have built into the kernel. With 256MB of RAM, though, this isn't likely to be a huge amount. Memory can be used by program data and program code. The latter can be shared between multiple instances of the same program, and shared libraries can be shared between multiple programs using the same library, so all of this shows up in the "shared" column of 'free'. Unsharable program data shows up in the "used" column (along with everything else). At this point, we've accounted for all of the memory that the system needs for programs. The third line of 'free's output (-/+ buffers/cache) has this information. On my system, there's 56MB of RAM, and 21588K is actually used. The kernel could just let the rest sit there and be wasted. Instead, it takes memory as is available and uses it as disk cache space. This makes the system run faster (since hopefully data needed from the disk will already be in memory), and has negligible cost (it's using memory that otherwise would be completely unused). If there's suddenly more demand for memory, the kernel can just throw away buffers and cache (the data exists for real on the disk) and use that space for programs and data. CH> Background is that it crashed on it's first day in production service with CH> a out-of-memory error displayed at the console - after two month working CH> idle in test mode. After that I upgraded this morning from 2.0.36 to 2.2.15. CH> I can't tell how exaktly the buffer behaviour was in 2.0.36 :-( The buffer behavior was the same in 2.0.36. :-) What exactly died, and what error exactly did it get? If you have a really large process, it might be running into the system limits; try typing 'ulimit -a' in bash (or other Bourne-shell derivatives) and see if you might be running into limits for various things. You can also use ulimit to change the limits; see the shell's man page for details. (In C-style shells, the relevant command is 'limit'.) -- David Maze [EMAIL PROTECTED] http://www.mit.edu/~dmaze/ "Theoretical politics is interesting. Politicking should be illegal." -- Abra Mitchell
