> On Oct 27, 2015, at 15:09, Minchan Kim <minc...@kernel.org> wrote:
>
> Hello Yalin,
>
> Sorry for missing you in Cc list.
> IIRC, mails to send your previous mail address(yalin.w...@sonymobile.com)
> were returned.
>
> You added comment bottom line so I'm not sure what PageDirty you meant.
>
>> it is wrong here if you only check PageDirty() to decide if the page is
>> freezable or not .
>> The Anon page are shared by multiple process, _mapcount > 1 ,
>> so you must check all pt_dirty bit during page_referenced() function,
>> see this mail thread:
>> http://ns1.ske-art.com/lists/kernel/msg1934021.html
>
> If one of pte among process sharing the page was dirty, the dirtiness should
> be propagated from pte to PG_dirty by try_to_unmap_one.
> IOW, if the page doesn't have PG_dirty flag, it means all of process did
> MADV_FREE.
>
> Am I missing something from you question?
> If so, could you show exact scenario I am missing?
>
> Thanks for the interest.
oh, yeah , that is right , i miss that , pte_dirty will propagate to PG_dirty ,
so that is correct .
Generic to say this patch move set_page_dirty() from add_to_swap() to
try_to_unmap(), i think can change a little about this patch:
@@ -1476,6 +1446,8 @@ static int try_to_unmap_one(struct page *page, struct
vm_area_struct *vma,
ret = SWAP_FAIL;
goto out_unmap;
}
+ if (!PageDirty(page))
+ SetPageDirty(page);
if (list_empty(&mm->mmlist)) {
spin_lock(&mmlist_lock);
if (list_empty(&mm->mmlist))
i think this 2 lines can be removed ,
since pte_dirty have propagated to set_page_dirty() , we don’t need this line
here ,
otherwise you will always dirty a AnonPage, even it is clean,
then we will page out this clean page to swap partition one more , this is not
needed.
am i understanding correctly ?
By the way, please change my mail address to yalin.wang2...@gmail.com in CC
list .
Thanks a lot. :)
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