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

----- Original Message ----- > > > > 在 2013年3月27日星期三，Dave Anderson 写道： > > > > > ----- 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(a)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?

> > 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.

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?