[Crash-utility] [PATCH 0/4] To support module percpu symbol
Toshikazu Nakayama
nakayama.ts at ncos.nec.co.jp
Tue Nov 9 07:51:36 UTC 2010
Hi Dave,
Thank you for welcome, review and testing.
>You've come to the right place... ;-)
>
>And your patch submission is fine, although I do prefer that you send the
>the patches as email attachments instead of inline. (Although that's my
>problem because of the Zimbra email client that I use)
Ok, I attach V2 patches. [PATCH 3/4] is updated.
>I tested your patch with two kernel types, one of them the "legacy" version
>with "pcpu_num_used" and "pcpu_size" symbols (RHEL5), and the second one with
>current kernels with the "pcpu_reserved_chunk_limit" symbol (RHEL6 and 2.6.37-rc1).
>
>Here's what I see, first without, and then with your patch applied.
>In any case, there's no way I can change the st->__per_cpu_end values
>as you propose -- even if it somehow works with your testing.
>
>Comments?
I did some wrong changes and would understand your mentions.
Updating __per_cpu_end itself makes original UI's corruption.
And for sure, I want __per_cpu_end to be bumped with your guess.
I fixed these bugs like attachments and tested again,
of course checked st->__per_cpu_end value advised from you.
One more update is to add is_per_cpu_range().
Because there are some conditions about percpu range in symbols.c,
I think it is better to use common function than inline.
The function returns 0 (not percpu), 1 (kernels) and 2 (modules)
although callers do not distinguish between 1 and 2 now.
Thanks,
Toshi
>(1) Testing with a 2.6.18-based RHEL5 kernel:
>
> Without your patch, the stored __per_cpu_start and __per_cpu_end
> values are as shown here in the symbol_table_data structure:
>
> crash> help -s
> ...
> __per_cpu_start: ffffffff80419000
> __per_cpu_end: ffffffff8041f508
> ...
>
> which reflect the beginning and end of the __per_cpu kernel
> symbol range:
>
> crash> sym -l
> ...
> ffffffff80419000 (A) __per_cpu_start
> ffffffff80419000 (D) per_cpu__init_tss
> ffffffff8041b080 (D) per_cpu__orig_ist
> ffffffff8041b100 (d) per_cpu__idle_state
> ...
> ffffffff8041f480 (d) per_cpu__flow_flush_tasklets
> ffffffff8041f4c0 (d) per_cpu__rt_cache_stat
> ffffffff8041f500 (d) per_cpu____icmp_socket
> ffffffff8041f508 (A) __per_cpu_end
>
> With your patch applied, the __per_cpu_end gets incremented based
> upon the "pcpu_num_used" and "pcpu_size" contents:
>
> crash> help -s
> ...
> __per_cpu_start: ffffffff80419000
> __per_cpu_end: ffffffff80427a10
> ...
>
> But that doesn't seem right, because the resultant value
> pushes it into the bss symbol range:
>
> crash> sym ffffffff80427a10
> ffffffff80427a10 (B) boot_exception_stacks+6672
> crash>
>
> crash> sym -l
> ...
> ffffffff8041f4c0 (d) per_cpu__rt_cache_stat
> ffffffff8041f500 (d) per_cpu____icmp_socket
> ffffffff8041f508 (A) __per_cpu_end <-- original value
> ffffffff80420000 (d) .data_nosave
> ffffffff80420000 (A) __nosave_begin
> ffffffff80420000 (D) in_suspend
> ffffffff80421000 (b) .bss
> ffffffff80421000 (A) __bss_start
> ffffffff80421000 (A) __nosave_end
> ffffffff80421000 (B) empty_zero_page
> ffffffff80422000 (B) boot_cpu_stack
> ffffffff80426000 (B) boot_exception_stacks <-- bumped to ffffffff80427a10
> ffffffff8042c000 (B) idt_table
> ffffffff8042d000 (B) boot_delay
> ffffffff8042d008 (B) printk_delay_msec
> ...
>
>(2) Testing with a 2.6.32-based RHEL6 kernel:
>
> Without your patch, the stored __per_cpu_start and __per_cpu_end
> values are as shown here in the symbol_table_data structure:
>
> crash> help -s
> ...
> __per_cpu_start: 0
> __per_cpu_end: 17358
> ...
>
> which reflect the beginning and end of the kernel's __per_cpu
> symbol range:
>
> crash> sym -l
> 0 (D) __per_cpu_start
> 0 (V) per_cpu__irq_stack_union
> 4000 (V) per_cpu__gdt_page
> 5000 (V) per_cpu__exception_stacks
> ...
> 16940 (V) per_cpu__cpu_tlbstate
> 16980 (V) per_cpu__runqueues
> 17340 (V) per_cpu__sched_clock_data
> 17358 (D) __per_cpu_end
> ffffffff81000000 (T) _text
> ...
>
> With your patch applied, the st->__per_cpu_end value gets changed
> like so:
>
> crash> help -s
> ...
> __per_cpu_start: 0
> __per_cpu_end: ffffffff81bf36b8
> ...
>
> But that doesn't seem right, where ffffffff81bf36b8 is the
> "pcpu_reserved_chunk_limit" symbol value:
>
> crash> sym ffffffff81bf36b8
> ffffffff81bf36b8 (b) pcpu_reserved_chunk_limit
> crash>
>
> I'm guessing that you want it st->__per_cpu_end to be bumped from
> 0x17358 to 0x19358:
>
> crash> px pcpu_reserved_chunk_limit
> pcpu_reserved_chunk_limit = $4 = 0x19358
> crash>
>
>(3) Testing with a generic upstream 2.6.37-rc1 kernel, I see the same
> behaviour as with the RHEL6 kernel.
>
>In any case, there's no way I can change the st->__per_cpu_end values
>as you propose -- even if it somehow works with your testing.
>
>Comments?
>
>Dave
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