linux-kernel - Re: [PATCH 20/35] Use a pre-calculated value for num_online

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.1.10.0903191841040.15549@qirst.com>
Date:	Thu, 19 Mar 2009 18:42:39 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mel Gorman <mel@....ul.ie>
cc:	Linux Memory Management List <linux-mm@...ck.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 20/35] Use a pre-calculated value for
 num_online_nodes()

On Thu, 19 Mar 2009, Mel Gorman wrote:

> I posted an amalgamation. Sorry for the cross-over mails but I wanted to
> get tests going before I fell asleep. They take a few hours to complete.
>
> > >  static inline void node_set_state(int node, enum node_states state)
> > >  {
> > >  	__node_set(node, &node_states[state]);
> > > +	if (state == N_ONLINE)
> > > +		nr_online_nodes = num_node_state(N_ONLINE);
> > >  }
> >
> > That assumes uses of node_set_state N_ONLINE. Are there such users or are
> > all using node_set_online()?
> >
>
> node_set_online() calls node_set_state(node, N_ONLINE) so it should have
> worked out.

But this adds a surprising side effect to all uses of node_set_state.
Node_set_state is generating more code now.

> > if you want to check if the system could ever bring up a second node
> > (which would make the current optimization not viable) whereas
> > nr_online_nodes is the check for how many nodes are currently online.
> >
>
> I redid your patch to drop the nr_possible_nodes() because I couldn't convince
> myself it was correct in all cases and it isn't as important as avoiding
> num_online_nodes() in fast paths.

I was more thinking about getting the infrastructure right so that we can
avoid future hacks like the one in slab.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/