On Tue, Jun 26, 2012 at 06:55:13PM +0200, Sebastian Andrzej Siewior wrote:

On Fri, Jun 22, 2012 at 03:30:31PM +0100, Mel Gorman wrote:

quoted

This is needed to allow network softirq packet processing to make
use of PF_MEMALLOC.

quoted

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b6c0727..5c6d9c6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c

@@ -2265,7 +2265,11 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
 	if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
 		if (gfp_mask & __GFP_MEMALLOC)
 			alloc_flags |= ALLOC_NO_WATERMARKS;
-		else if (likely(!(gfp_mask & __GFP_NOMEMALLOC)) && !in_interrupt())
+		else if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
+			alloc_flags |= ALLOC_NO_WATERMARKS;
+		else if (!in_interrupt() &&
+				((current->flags & PF_MEMALLOC) ||
+				 unlikely(test_thread_flag(TIF_MEMDIE))))
 			alloc_flags |= ALLOC_NO_WATERMARKS;
 	}

You allocate in RX path with __GFP_MEMALLOC and your sk->sk_allocation has
also __GFP_MEMALLOC set. That means you should get ALLOC_NO_WATERMARKS in
alloc_flags.

In the cases where they are annotated correctly, yes. It is recordeed if
the page gets allocated from the PFMEMALLOC reserves. If the received
packet is not SOCK_MEMALLOC and the page was allocated from PFMEMALLOC
reserves it is then discarded and the packet must be retransmitted.

Is this to done to avoid GFP annotations in skb_share_check() and
friends on your __netif_receive_skb() path?

I don't get your question as the annotations are not being avoided. If they
are set, they are used. In the __netif_receive_skb path, PF_MEMALLOC is
set for PFMEMALLOC skbs to avoid having to annotate every single allocation
call site.

-- 
Mel Gorman
SUSE Labs

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