Re: [Crash-utility] [PATCH v2] Add -m option to kmem

----- Original Message ----- > > ----- Original Message ----- >>> kmem -m|-M is used for displaying information of all ksm pages or >>> some ksm pages for specified ksm stable tree node addresses >>> >>> for example: >>> crash> kmem -m >>> STABLE_NODE : ffff88083fc927e0 >>> PAGE : ffffea000e667998 >>> PHYSICAL ADDRESS: 41d475000 >>> >>> PID: 2967 MAPPING: 3 >>> >>> STABLE_NODE : ffff88083fc84a10 >>> PAGE : ffffea000e3dd5d8 >>> PHYSICAL ADDRESS: 411aad000 >>> >>> PID: 2967 MAPPING: 7 >>> >>> STABLE_NODE : ffff88041980dda8 >>> PAGE : ffffea000e335568 >>> PHYSICAL ADDRESS: 40eaab000 >>> >>> PID: 2967 MAPPING: 8 >>> ... >>> >>> STABLE_NODE : ffff880841ea43f8 >>> PAGE : ffffea000f62de38 >>> PHYSICAL ADDRESS: 465641000 >>> >>> PID: 2967 MAPPING: 729 >>> PID: 3017 MAPPING: 499 >>> >>> P.S. >>> This patch is based on the patch from Qiao(qiaonuohan cn fujitsu com ) >>> 0001-make-rbtree-manipulation-functions-global.patch >>> Because this patch also uses rb_tree operations. >> >> I cannot test this because all of my sample dumps either return: >> >> crash> kmem -m >> kmem: -m option not supported or applicable on this architecture or >> kernel >> crash> >> >> this is the kernel that doesn't support ksm >> >> or: >> >> crash> kmem -m >> ksm may not be enabled >> crash> >> >> This is because ksm is disabled or there is no ksm page in your >> system. > > Which one? Can't you determine that? I will change the message to: no ksm pages in the system meaning that there is not any ksm page in the system. > >> >> which, by the way, is not a very helpful error message. >> >> Do you have a reasonably-sized vmcore that I can download and test? >> >> I have no vmcore on hand now. You could follow the below steps to >> make ksm work in your system. >> >> * Ensure you are using kernel >= 2.6.31-0.94.rc4.fc12 and qemu-kvm >=0.10.92-4.fc12 >> * Run two or more similar virtual machines >> * service ksm start >> * service ksmtuned start >> * Wait a while >> * Check whether pages were merged using /sys/kernel/mm/ksm/pages_shared >> * If value in /sys/kernel/mm/ksm/pages_shared is not zero, you >> could run crash kmem -m to see the output. > > OK look, if I get the time, I'll try to set this up... > > But just the fact that I have to go to all this trouble, and the fact > that you don't even have a sample vmcore available again begs the question > as to how useful -- or better put -- how often, this command would ever > be utilized. Sorry about this. I will make a vmcore and tell where you can download it later. > > On the other hand, if you were to create a "ksm" extension module, then > I would be more than happy to post it with all of the others on the > extensions web page. > >> Also, I have a question about the help message: >> >> crash> help kmem >> >> NAME >> kmem - kernel memory >> >> SYNOPSIS >> kmem [-f|-F|-p|-c|-C|-i|-s|-S|-v|-V|-n|-z|-o|-m|-M] [slab] [[-P] >> address] >> [-g [flags] >> >> DESCRIPTION >> ... [ cut ] ... >> -m displays information of ksm pages. >> -M same as -m, but also dumps virtual addresses that mapping the >> ksm pages. >> ... [ cut ] ... >> address when used with -m or -M, the address can be either a ksm stable >> tree node address, a page's physical address, or a page pointer, >> the information of the ksm page (if it is) is displayed. >> ... [ cut ] ... >> >> Display information of ksm pages: >> >> crash> kmem -m ffff88086f22eec0 ffff8803573964c0 >> STABLE_NODE : ffff88083fc927e0 >> PAGE : ffffea000e667998 >> PHYSICAL ADDRESS: 41d475000 >> >> PID: 2967 MAPPING: 3 >> >> STABLE_NODE : ffff88083fc84a10 >> PAGE : ffffea000e3dd5d8 >> PHYSICAL ADDRESS: 411aad000 >> >> PID: 2967 MAPPING: 7 >> >> STABLE_NODE : ffff88041980dda8 >> PAGE : ffffea000e335568 >> PHYSICAL ADDRESS: 40eaab000 >> >> PID: 2967 MAPPING: 8 >> >> ...... >> >> STABLE_NODE : ffff880841ea43f8 >> PAGE : ffffea000f62de38 >> PHYSICAL ADDRESS: 465641000 >> >> PID: 2967 MAPPING: 729 >> PID: 3017 MAPPING: 499 >> >> crash> >> >> Please tell me how the two address arguments ffff88086f22eec0 and >> ffff8803573964c0 have any relationship to the subsequent display? >> >> >> Sorry this is a mistake. The two addresses in the example are >> redundant. > > Well, they aren't "redundant", they just don't make any sense at all. > I'm presuming that they don't belong there at all, and that you're > just showing the output of "kmem -m" alone, correct? Yes, you are right. Thanks Zhang