On Fri, 22 Jul 2005, Bernd Petrovitsch wrote: > On Fri, 2005-07-22 at 08:27 -0300, Vinicius wrote: > [...] >> I have a server with 2 Pentium 4 HT processors and 32 GB of RAM, this >> server runs lots of applications that consume lots of memory to. When I stop >> this applications, the kernel doesn't free memory (the memory still in use) >> and the server cache lots of memory (~27GB). When I start this applications, >> the kernel sends "Out of Memory" messages and kill some random >> applications. >> >> Anyone know how can I reduce the kernel cached memory on RHEL 3 (kernel >> 2.4.21-32.ELsmp - Trial version)? There is a way to reduce the kernel cached >> memory utilization? > > Probably RedHat's support can answer this for RHEL 3. > > Bernd > --
> Firmix Software GmbH http://www.firmix.at/ > mobil: +43 664 4416156 fax: +43 1 7890849-55 > Embedded Linux Development and Services > How do you know the memory is "still in use?" I think that if you run a program that uses so much memory that some swap is used, but not allowing all free memory to be exhausted, you can run the same program over and over again forever. Therefore, the memory must have been freed and available for the next time you run the program. The problem is that you are exhausting all free memory causing the kernel to kill processes just to stay alive. Then you look at some memory "tool" and think that it shows something about what is, or has been freed. You need to set process limits on the amount of resources each process can use and, depending upon the implementation details of your "server", you might even need to turn memory over-commit off: echo "0" > /proc/sys/vm/overcommit_memory The fact is that unused memory is stored in caches and buffers. That's how it doesn't get wasted. In fact, with a busy system an attempt is made to use all available real RAM and minimize swap. Some server programs are written much like your defective test program. You can't attempt to allocate all virtual memory using malloc(), expecting it to return NULL when there is no more. Malloc() will return NULL when it has gotten trashed by somebody overwriting buffer boundaries or when address-space is exhausted. It has no clue how much RAM is available and, in fact if it did, it would represent an information leak. Programs should allocate what they need, not what they can get. Cheers, Dick Johnson Penguin : Linux version 2.6.12 on an i686 machine (5537.79 BogoMips). Warning : 98.36% of all statistics are fiction. . **************************************************************** The information transmitted in this message is confidential and may be privileged. Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited. If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to [EMAIL PROTECTED] - and destroy all copies of this information, including any attachments, without reading or disclosing them. Thank you. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
