From: NeilBrown <neilb@suse.de>
To: Mel Gorman <mgorman@suse.de>
Cc: Linux-MM <linux-mm@kvack.org>,
Linux-Netdev <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
David Miller <davem@davemloft.net>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH 09/13] netvm: Set PF_MEMALLOC as appropriate during SKB processing
Date: Wed, 27 Apr 2011 09:22:03 +1000 [thread overview]
Message-ID: <20110427092203.659fbc25@notabene.brown> (raw)
In-Reply-To: <20110426141048.GG4658@suse.de>
On Tue, 26 Apr 2011 15:10:48 +0100 Mel Gorman <mgorman@suse.de> wrote:
> On Tue, Apr 26, 2011 at 10:21:57PM +1000, NeilBrown wrote:
> > On Tue, 26 Apr 2011 08:36:50 +0100 Mel Gorman <mgorman@suse.de> wrote:
> >
> > > diff --git a/net/core/dev.c b/net/core/dev.c
> > > index 3871bf6..2d79a20 100644
> > > --- a/net/core/dev.c
> > > +++ b/net/core/dev.c
> > > @@ -3095,6 +3095,27 @@ static void vlan_on_bond_hook(struct sk_buff *skb)
> > > }
> > > }
> > >
> > > +/*
> > > + * Limit which protocols can use the PFMEMALLOC reserves to those that are
> > > + * expected to be used for communication with swap.
> > > + */
> > > +static bool skb_pfmemalloc_protocol(struct sk_buff *skb)
> > > +{
> > > + if (skb_pfmemalloc(skb))
> > > + switch (skb->protocol) {
> > > + case __constant_htons(ETH_P_ARP):
> > > + case __constant_htons(ETH_P_IP):
> > > + case __constant_htons(ETH_P_IPV6):
> > > + case __constant_htons(ETH_P_8021Q):
> > > + break;
> > > +
> > > + default:
> > > + return false;
> > > + }
> > > +
> > > + return true;
> > > +}
> >
> > This sort of thing really bugs me :-)
> > Neither the comment nor the function name actually describe what the function
> > is doing. The function is checking *2* things.
> > is_pfmemalloc_skb_or_pfmemalloc_protocol()
> > might be a more correct name, but is too verbose.
> >
> > I would prefer the skb_pfmemalloc test were removed from here and ....
> >
> > > + if (!skb_pfmemalloc_protocol(skb))
> > > + goto drop;
> > > +
> >
> > ...added here so this becomes:
> >
> > if (!skb_pfmemalloc(skb) && !skb_pfmemalloc_protocol(skb))
> > goto drop;
> >
> > which actually makes sense.
> >
>
> Moving the check is neater but that check should be
>
> if (skb_pfmemalloc(skb) && !skb_pfmemalloc_protocol(skb))
>
> ? It's only if the skb was allocated from emergency reserves that we
> need to consider dropping it to make way for other packets to be
> received.
>
Correct. I got my Boolean algebra all confused. Sorry 'bout that.
NeilBrown
--
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/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-04-26 23:22 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-26 7:36 [PATCH 00/13] Swap-over-NBD without deadlocking Mel Gorman
2011-04-26 7:36 ` [PATCH 01/13] mm: Serialize access to min_free_kbytes Mel Gorman
2011-04-26 7:36 ` [PATCH 02/13] mm: sl[au]b: Add knowledge of PFMEMALLOC reserve pages Mel Gorman
2011-04-26 11:15 ` NeilBrown
2011-04-26 11:33 ` Mel Gorman
2011-04-26 12:05 ` NeilBrown
2011-04-26 11:37 ` NeilBrown
2011-04-26 13:59 ` Mel Gorman
2011-04-27 23:21 ` NeilBrown
2011-04-28 9:46 ` Mel Gorman
2011-04-26 7:36 ` [PATCH 03/13] mm: Introduce __GFP_MEMALLOC to allow access to emergency reserves Mel Gorman
2011-04-26 9:49 ` NeilBrown
2011-04-26 10:36 ` Mel Gorman
2011-04-26 10:53 ` NeilBrown
2011-04-26 14:00 ` Mel Gorman
2011-04-26 7:36 ` [PATCH 04/13] mm: allow PF_MEMALLOC from softirq context Mel Gorman
2011-04-26 7:36 ` [PATCH 05/13] mm: Ignore mempolicies when using ALLOC_NO_WATERMARK Mel Gorman
2011-04-26 7:36 ` [PATCH 06/13] net: Introduce sk_allocation() to allow addition of GFP flags depending on the individual socket Mel Gorman
2011-04-26 7:36 ` [PATCH 07/13] netvm: Allow the use of __GFP_MEMALLOC by specific sockets Mel Gorman
2011-04-26 7:36 ` [PATCH 08/13] netvm: Allow skb allocation to use PFMEMALLOC reserves Mel Gorman
2011-04-26 7:36 ` [PATCH 09/13] netvm: Set PF_MEMALLOC as appropriate during SKB processing Mel Gorman
2011-04-26 12:21 ` NeilBrown
2011-04-26 14:10 ` Mel Gorman
2011-04-26 23:22 ` NeilBrown [this message]
2011-04-26 7:36 ` [PATCH 10/13] mm: Micro-optimise slab to avoid a function call Mel Gorman
2011-04-26 7:36 ` [PATCH 11/13] nbd: Set SOCK_MEMALLOC for access to PFMEMALLOC reserves Mel Gorman
2011-04-26 7:36 ` [PATCH 12/13] mm: Throttle direct reclaimers if PF_MEMALLOC reserves are low and swap is backed by network storage Mel Gorman
2011-04-26 12:30 ` NeilBrown
2011-04-26 14:26 ` Mel Gorman
2011-04-26 23:18 ` NeilBrown
2011-04-27 8:36 ` Mel Gorman
2011-04-26 7:36 ` [PATCH 13/13] mm: Account for the number of times direct reclaimers get throttled Mel Gorman
2011-04-26 12:35 ` NeilBrown
2011-04-26 14:26 ` Mel Gorman
2011-04-26 14:23 ` [PATCH 00/13] Swap-over-NBD without deadlocking Peter Zijlstra
2011-04-26 14:46 ` Mel Gorman
2011-04-26 14:50 ` Peter Zijlstra
2011-04-27 8:43 ` Mel Gorman
2011-04-28 13:31 ` Pavel Machek
2011-04-28 13:42 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2011-04-27 16:07 [PATCH 00/13] Swap-over-NBD without deadlocking v3 Mel Gorman
2011-04-27 16:08 ` [PATCH 09/13] netvm: Set PF_MEMALLOC as appropriate during SKB processing Mel Gorman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110427092203.659fbc25@notabene.brown \
--to=neilb@suse.de \
--cc=a.p.zijlstra@chello.nl \
--cc=davem@davemloft.net \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).