[Crash-utility] Crash shows - Invalid Memory size

Hi We encountered this problem with Crash showing invalid memory when ran on live machine: ====================================== [root@venuslp11 ~]# free -m total used free shared buffers cached Mem: 2151 1594 557 0 583 795 ^^^^^^ -/+ buffers/cache: 215 1935 Swap: 1983 0 1983 [root@venuslp11 ~]# cat /proc/ppc64/lparcfg | grep DesMem DesMem=2304 ^^^^^^ [root@venuslp11 ~]# rpm -q crash crash-4.0-3.7 [root@venuslp11 ~]# crash ... KERNEL: /usr/lib/debug/lib/modules/2.6.18-1.2732.el5/vmlinux DUMPFILE: /dev/mem CPUS: 2 DATE: Fri Oct 27 07:58:54 2006 UPTIME: 01:12:34 LOAD AVERAGE: 1.52, 1.05, 0.48 TASKS: 98 NODENAME: venuslp11.upt.austin.ibm.com RELEASE: 2.6.18-1.2732.el5 VERSION: #1 SMP Tue Oct 17 18:24:27 EDT 2006 MACHINE: ppc64 (2301 Mhz) MEMORY: 3.2 GB ^^^^^^^^ PID: 25097 COMMAND: "crash" TASK: c000000000fedbe0 [THREAD_INFO: c00000000b190000] CPU: 0 STATE: TASK_RUNNING (ACTIVE) crash> ================================== As I looked into the code I found: The differences are observed because of the different way in which they(proc and crash) are implemented to calculate Total Memory. In /proc/meminfo it traverse through the memory counting each page and it has different routines to calculate No of pages in highmem, init section, bootmem etc. Which may be difficult to implement with Crash. Instead we can look into sys file implementation(/sys/devices/system/node/node<n>/meminfo). Here the Total Page is got not from unsigned long node_spanned_pages but from long node_present_pages. The definitions of node_present_pages says 'total number of physical pages' while node_spanned_pages says 'total size of physical page range, including holes'. This is observed because of way Node 2 is spread in the machine its pfn(physical frame number) starts from 0 while that of 0th and 1st node starts from 4096 and 8192 pfns respectively. so node3->spanned_pages has double counted value from even the node 0 and node 1. Hence I feel its better to use present_pages which has only the pages from the node excluding the holes. ====================================== The patch to fix the problem: Let me know of your opinion..