From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Seth, Rohit" Date: Thu, 14 Mar 2002 23:13:35 +0000 Subject: RE: [Linux-ia64] Kernel Shared Memory Max (shmmax) Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org shmmax is the size of largest shared memory (in bytes) segment that the kernel allows. System wide value of total shared memory value is given by shmall parameter. Currently the default value for shmmax is (extrememly low) 32MB. And based on that the total amount of shared memory segment that can be created in IA-64 platform (with 16K page size) is 8G. There is no direct relationship between shmmax value and the amount of physical memory available in the system. Though you will never be able to create a shared memory segment bigger then the total memory (Free RAM+Free SWAP) available on the machine (unless you change the sysctl_overcommit_memory). Besides that, this low default value of 32MB just adds overhead for big memory systems. It will be nice to change this default value to 2G at least for IA-64 machines. You can also change this value of shm* (shmmax etc.) by writing proper values in /proc/sys/kernel/shm* rohit -----Original Message----- From: Donny Cooper [mailto:dcooper@atcc.necsys.com] Sent: Thursday, March 14, 2002 2:40 PM To: ia64-list@redhat.com; linux-ia64@linuxia64.org Subject: [Linux-ia64] Kernel Shared Memory Max (shmmax) Does the maximum possible shared memory (shmmax) increase with the Enterprise kernel? Below is from doc/sysctl/kernel.txt document. Is this document valid for IA-64 kernel? It seems you can set this value to pretty much anything (even larger than the available memory), so I'm assuming the value gets intelligently truncated to the max supported. How can I check how much shared mem is available, `free` or `top` just shows what's used, right? ...doc/sysctl/kernel.txt =============================== shmmax: This value can be used to query and set the run time limit on the maximum shared memory segment size that can be created. Shared memory segments up to 1Gb are now supported in the kernel. This value defaults to SHMMAX. =============================== Thanks, ----------------------------------- Donny Cooper NEC Systems, Inc. Advanced Technical Computing Center dcooper@atcc.necsys.com ----------------------------------- _______________________________________________ Linux-IA64 mailing list Linux-IA64@linuxia64.org http://lists.linuxia64.org/lists/listinfo/linux-ia64