Re: [Crash-utility] [PATCH] Add -m option to kmem
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@cn.fujitsu.com<javascript:;>
)
> 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, 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.
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.
Dave
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