Re: [PATCH] net: use non-compound pages in frag allocator

On Thu, 2016-08-04 at 13:38 +0000, Ilya Lesokhin wrote:

You are right I just realized that this patch causes a memory leak, so sorry for the spam.

I just had problem understanding when compound pages are needed and when It is enough to use an high order pages.
I thought that that high order pages are enough for this use case, tested it and saw no problems.

Unfortunately it seems you must use compound pages to keep track of  the page order.
put_page assumes that the order of a non-compound page is always 0. 
It would be nice to document it somewhere but I'm not sure where.

Please do not top-post on netdev mailing list.

( Documentation/development-process/2.Process : line 422 )

AFAIK, only when we can call free_pages(p, order) and provide @order, we
can avoid using __GFP_COMP at alloc time.

But if some path has to use put_page(), then we are forced to use
__GFP_COMP for high order pages.

Thanks.