Date: Mon, 29 Oct 2012 12:01:07 -0700
From: Tejun Heo <tj@kernel.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Sasha Levin <levinsasha928@gmail.com>,
        Josh Triplett <josh@joshtriplett.org>, torvalds@linux-foundation.org,
        akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, paul.gortmaker@windriver.com, davem@davemloft.net,
        rostedt@goodmis.org, mingo@elte.hu, ebiederm@xmission.com,
        aarcange@redhat.com, ericvh@gmail.com, netdev@vger.kernel.org,
        eric.dumazet@gmail.com, axboe@kernel.dk, agk@redhat.com,
        dm-devel@redhat.com, neilb@suse.de, ccaulfie@redhat.com,
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        fweisbec@gmail.com, jesse@nicira.com, venkat.x.venkatsubra@oracle.com,
        ejt@redhat.com, snitzer@redhat.com, edumazet@google.com,
        linux-nfs@vger.kernel.org, dev@openvswitch.org,
        rds-devel@oss.oracle.com, lw@cn.fujitsu.com
Subject: Re: [PATCH v7 06/16] tracepoint: use new hashtable implementation
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On Mon, Oct 29, 2012 at 11:58:14AM -0700, Tejun Heo wrote:
> On Mon, Oct 29, 2012 at 02:53:19PM -0400, Mathieu Desnoyers wrote:
> > The argument about hash_init being useful to add magic values in the
> > future only works for the cases where a hash table is declared with
> > DECLARE_HASHTABLE(). It's completely pointless with DEFINE_HASHTABLE(),
> > because we could initialize any debugging variables from within
> > DEFINE_HASHTABLE().
> 
> You can do that with [0 .. HASH_SIZE - 1] initializer.

And in general, let's please try not to do optimizations which are
pointless.  Just stick to the usual semantics.  You have an abstract
data structure - invoke the initializer before using it.  Sure,
optimize it if it shows up somewhere.  And here, if we do the
initializers properly, it shouldn't cause any more actual overhead -
ie. DEFINE_HASHTABLE() will basicallly boil down to all zero
assignments and the compiler will put the whole thing in .bss anyway.

Thanks.

-- 
tejun
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