On 02/15/2010 11:00 AM, Rik van Riel wrote:
> On 02/15/2010 10:50 AM, Chris Friesen wrote:
>
>> Looking at the code, it looks like page_remove_rmap() clears the
>> Anonpage flag and removes it from NR_ANON_PAGES, and the caller is
>> responsible for removing it from the LRU. Is that right?
>
> Nope.
>
>> I'll keep digging in the code, but does anyone know where the removal
>> from the LRU is supposed to happen in the above code paths?
>
> Removal from the LRU is done from the page freeing code, on
> the final free of the page.
>
> It appears you have code somewhere that increments the reference
> count on user pages and then forgets to lower it afterwards.
Okay, that makes sense.
I'm still trying to get a handle on the LRU removal though. The code
path that I saw most which resulted in clearing the anon bit but leaving
the page on the LRU was the following:
[<ffffffff8029c951>] kmemleak_clear_anon+0x7f/0xbe
[<ffffffff802864c7>] page_remove_rmap+0x45/0x146
[<ffffffff8027dc7e>] unmap_vmas+0x41c/0x948
[<ffffffff80282405>] exit_mmap+0x7b/0x108
[<ffffffff8022f441>] mmput+0x33/0x110
[<ffffffff80233b05>] exit_mm+0x103/0x130
[<ffffffff802355b5>] do_exit+0x17b/0x91f
[<ffffffff80235d95>] do_group_exit+0x3c/0x9c
[<ffffffff80235e07>] sys_exit+0x0/0x12
[<ffffffff8021ddb5>] ia32_syscall_done+0x0/0xa
There are a bunch of inline functions involved, but I think the chain
from page_remove_rmap() back up to unmap_vmas() looks like this:
page_remove_rmap
zap_pte_range
zap_pmd_range
zap_pud_range
unmap_page_range
unmap_vmas
So in this scenario, where do the pages actually get removed from the
LRU list (assuming that they're not in use by anyone else)?
Thanks,
Chris
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