Messages in this thread | | | Date | Mon, 18 Oct 2010 14:52:19 +0900 | Subject | Re: [RFC][PATCH 3/3] alloc contig pages with migration. | From | Minchan Kim <> |
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On Mon, Oct 18, 2010 at 2:31 PM, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote: > On Mon, 18 Oct 2010 14:18:52 +0900 > Minchan Kim <minchan.kim@gmail.com> wrote: >> > >> >> > + * >> >> > + * Search an area of @size in the physical memory map and checks wheter >> >> >> >> Typo >> >> whether >> >> >> >> > + * we can create a contigous free space. If it seems possible, try to >> >> > + * create contigous space with page migration. If no_search==true, we just try >> >> > + * to allocate [hint, hint+size) range of pages as contigous block. >> >> > + * >> >> > + * Returns a page of the beginning of contiguous block. At failure, NULL >> >> > + * is returned. Each page in the area is set to page_count() = 1. Because >> >> >> >> Why do you mention page_count() = 1? >> >> Do users of this function have to know it? >> > >> > A user can free any page within the range for his purpose. >> >> I think it's not a good idea if we allow handling of page by page, not >> for page-chunk requested by user. >> By mistake, free_contig_pages could have a trouble to free pages. >> Why do you support the feature? Do you have any motivation? >> > No big motivation. > > Usual pages are set up by prep_compund_page(page, order), but it is pages smaller > than MAX_ORDER. Then, I called prep_new_page() one by one. > And I don't think some new prep_xxxx_page() is required. > > If you requests, ok, I'll add one.
Maybe we are talking another thing.
My question is why you noticed "page_count() == 1" in function description. So your answer was for user to free some pages within big contiguous page. Then, my concern is that if you didn't mentioned page_count() == 1 in description, anonymous user will use just alloc_contig_pages and free_contig_pages. That's enough for current our requirement. But since you mentioned page_count() == 1 and you want for user to free some pages within big contiguous page, anonymous user who isn't expert in mm or careless people can free pages _freely_. It could make BUG easily(free_contig_pages can free the page which is freed by user's put_page).
So if there isn't strong cause, I hope removing the mention for preventing careless API usage.
> > Thanks, > -Kame > >
-- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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