From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx156.postini.com [74.125.245.156]) by kanga.kvack.org (Postfix) with SMTP id D531D6B0071 for ; Wed, 27 Jun 2012 04:26:21 -0400 (EDT) Date: Wed, 27 Jun 2012 09:26:14 +0100 From: Mel Gorman Subject: Re: [PATCH 04/16] mm: allow PF_MEMALLOC from softirq context Message-ID: <20120627082614.GE8271@suse.de> References: <1340375443-22455-1-git-send-email-mgorman@suse.de> <1340375443-22455-5-git-send-email-mgorman@suse.de> <20120626165513.GD6509@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20120626165513.GD6509@breakpoint.cc> Sender: owner-linux-mm@kvack.org List-ID: To: Sebastian Andrzej Siewior Cc: Andrew Morton , Linux-MM , Linux-Netdev , LKML , David Miller , Neil Brown , Peter Zijlstra , Mike Christie , Eric B Munson , Eric Dumazet 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: > > This is needed to allow network softirq packet processing to make > > use of PF_MEMALLOC. > > > 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org