From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 19 Apr 2001 17:39:23 +0200 (MEST) From: Simon Derr Subject: Want to allocate almost all the memory with no swap Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: linux-mm@kvack.org Cc: Simon Derr List-ID: Hi, I'm currently trying to run a high-performance bench on a cluster of PCs under Linux. This bench is the Linpack test, and needs a lot of memory to store a matrix of numbers. Linpack needs to allocate as much as 240 Megs on a machine that has 256 Megs of RAM, but I have to be sure that the memory used by linpack will never be swapped on the disk. The bests results I have obtained so far are the following: * Under Linux 2.4.2: -With swap on, part of the memory used by my process is swapped out, which is what I do not want -With swap off:The memory allocation is OK, my process has all the memory it needs and can use it. BUT : here is what I get when running top: CPU states: 49.6% user, 50.3% system, 0.0% nice, 0.0% idle Mem: 254692K av, 252596K used, 2096K free, 0K shrd 68Kbuff Swap: 0K av, 0K used, 0K free 880Kcached PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME COMMAND 3 root 16 0 0 0 0 DW 0 49.6 0.0 11:10 kswapd 1142 admin 18 0 240M 240M 4 R 0 49.6 96.5 9:14 loop 5 root 9 0 0 0 0 SW 0 0.5 0.0 0:12 bdflush 1149 root 11 0 408 408 240 R 0 0.3 0.1 0:03 top (loop is the name of my process) kswapd uses half of my CPU, and even bdflush seems to eat some cpu. I find a bit weird to see kswapd eat my CPU when I have no swap at all... * Under Linux 2.2.17: -With swap on, same pb as under 2.4.2 -With swap off, the memory allocation fails. I tried to tune the values under /proc/sys/vm, with no success. Any ideas ? (Please CC me in the reply) Thanks, Simon. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux.eu.org/Linux-MM/