From: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
To: Mel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>,
Linux-Netdev <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
David Miller <davem@davemloft.net>, Neil Brown <neilb@suse.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Mike Christie <michaelc@cs.wisc.edu>,
Eric B Munson <emunson@mgebm.net>,
Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH 04/16] mm: allow PF_MEMALLOC from softirq context
Date: Sun, 8 Jul 2012 20:12:11 +0200 [thread overview]
Message-ID: <20120708181211.GE2872@breakpoint.cc> (raw)
In-Reply-To: <20120627082614.GE8271@suse.de>
On Wed, Jun 27, 2012 at 09:26:14AM +0100, Mel Gorman wrote:
> > > 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.
Let me try again:
- lets assume your allocation happens with alloc_page(), without
__GFP_MEMALLOC in GFP_FLAGS and with PF_MEMALLOC in current->flags. Now
you may get memory which you wouldn't receive otherwise (without
PF_MEMALLOC). Okay, understood. So you don't have to annotate each page
allocation in your receive path for instance as long as the process has the
flag set.
- lets assume your allocation happens with kmalloc() without __GFP_MEMALLOC
and current->flags has PF_MEMALLOC ORed and your SLAB pool is empty. This
forces SLAB to allocate more pages from the buddy allocator with it will
receive more likely (due to ->current->flags + PF_MEMALLOC) but SLAB will
drop this extra memory because the page has ->pf_memory (or something like
that) set and the GFP_FLAGS do not have __GFP_MEMALLOC set.
Is there something I missed?
Sebastian
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next prev parent reply other threads:[~2012-07-08 18:12 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-22 14:30 [PATCH 00/17] Swap-over-NBD without deadlocking V13 Mel Gorman
2012-06-22 14:30 ` [PATCH 01/16] mm: sl[au]b: Add knowledge of PFMEMALLOC reserve pages Mel Gorman
2012-06-22 14:30 ` [PATCH 02/16] mm: slub: Optimise the SLUB fast path to avoid pfmemalloc checks Mel Gorman
2012-06-22 14:30 ` [PATCH 03/16] mm: Introduce __GFP_MEMALLOC to allow access to emergency reserves Mel Gorman
2012-06-22 14:30 ` [PATCH 04/16] mm: allow PF_MEMALLOC from softirq context Mel Gorman
2012-06-26 16:55 ` Sebastian Andrzej Siewior
2012-06-27 8:26 ` Mel Gorman
2012-07-08 18:12 ` Sebastian Andrzej Siewior [this message]
2012-07-09 10:04 ` Mel Gorman
2012-07-09 16:57 ` Sebastian Andrzej Siewior
2012-07-10 11:09 ` Mel Gorman
2012-06-22 14:30 ` [PATCH 05/16] mm: Only set page->pfmemalloc when ALLOC_NO_WATERMARKS was used Mel Gorman
2012-06-22 14:30 ` [PATCH 06/16] mm: Ignore mempolicies when using ALLOC_NO_WATERMARK Mel Gorman
2012-06-22 14:30 ` [PATCH 07/16] net: Introduce sk_gfp_atomic() to allow addition of GFP flags depending on the individual socket Mel Gorman
2012-06-22 14:30 ` [PATCH 08/16] netvm: Allow the use of __GFP_MEMALLOC by specific sockets Mel Gorman
2012-06-22 14:30 ` [PATCH 09/16] netvm: Allow skb allocation to use PFMEMALLOC reserves Mel Gorman
2012-06-26 15:27 ` Sebastian Andrzej Siewior
2012-06-27 8:32 ` Mel Gorman
2012-06-22 14:30 ` [PATCH 10/16] netvm: Propagate page->pfmemalloc to skb Mel Gorman
2012-06-22 14:30 ` [PATCH 11/16] netvm: Propagate page->pfmemalloc from skb_alloc_page " Mel Gorman
2012-06-26 20:13 ` Sebastian Andrzej Siewior
2012-06-27 8:43 ` Mel Gorman
2012-07-09 19:18 ` Sebastian Andrzej Siewior
2012-07-10 11:12 ` Mel Gorman
2012-06-22 14:30 ` [PATCH 12/16] netvm: Set PF_MEMALLOC as appropriate during SKB processing Mel Gorman
2012-06-22 14:30 ` [PATCH 13/16] mm: Micro-optimise slab to avoid a function call Mel Gorman
2012-06-22 14:30 ` [PATCH 14/16] nbd: Set SOCK_MEMALLOC for access to PFMEMALLOC reserves Mel Gorman
2012-06-22 14:30 ` [PATCH 15/16] mm: Throttle direct reclaimers if PF_MEMALLOC reserves are low and swap is backed by network storage Mel Gorman
2012-06-22 14:30 ` [PATCH 16/16] mm: Account for the number of times direct reclaimers get throttled Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2012-06-29 13:32 [PATCH 00/16] Swap-over-NBD without deadlocking V14 Mel Gorman
2012-06-29 13:32 ` [PATCH 04/16] mm: allow PF_MEMALLOC from softirq context Mel Gorman
2012-07-12 6:40 [PATCH 00/16] Swap-over-NBD without deadlocking V15 Mel Gorman
2012-07-12 6:40 ` [PATCH 04/16] mm: allow PF_MEMALLOC from softirq context Mel Gorman
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