From: Tejun Heo <tj@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sasha Levin <levinsasha928@gmail.com>,
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
Subject: Re: [RFC v2 1/7] hashtable: introduce a small and naive hashtable
Date: Fri, 3 Aug 2012 17:05:31 -0700 [thread overview]
Message-ID: <20120804000531.GP15477@google.com> (raw)
In-Reply-To: <CA+55aFwTa_kYgmFwoWa6hwAAM6=2xTgQQf-vEx_gCzpEMnxodQ@mail.gmail.com>
Hello,
On Fri, Aug 03, 2012 at 04:47:47PM -0700, Linus Torvalds wrote:
> On Fri, Aug 3, 2012 at 3:36 PM, Tejun Heo <tj@kernel.org> wrote:
> >
> > I suppose you mean unsized. I remember this working. Maybe I'm
> > confusing it with zero-sized array. Hmm... gcc doesn't complain about
> > the following. --std=c99 seems happy too.
>
> Ok, I'm surprised, but maybe it's supposed to work if you do it inside
> another struct like that, exactly so that you can preallocate things..
Yeah, I think the rule is var array should be the last member of any
given struct definition. Once a struct is defined, its alignment and
size are fixed and it behaves like any other struct.
> Or maybe it's just a gcc bug. I do think this all is way hackier than
> Sasha's original simple code that didn't need these kinds of games,
> and didn't need a size member at all.
>
> I really think all the extra complexity and overhead is just *bad*.
> The first simple version was much nicer and likely generated better
> code too.
The size member could have performance impact in extreme cases. If
we're looking for something simple & fast, maybe just pass in @size as
argument and be done with it?
Thanks.
--
tejun
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next prev parent reply other threads:[~2012-08-04 0:05 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-03 14:23 [RFC v2 0/7] generic hashtable implementation Sasha Levin
2012-08-03 14:23 ` [RFC v2 1/7] hashtable: introduce a small and naive hashtable Sasha Levin
2012-08-03 17:15 ` Tejun Heo
2012-08-03 17:16 ` Tejun Heo
2012-08-03 21:19 ` Sasha Levin
2012-08-03 21:30 ` Tejun Heo
2012-08-03 21:36 ` Sasha Levin
2012-08-03 21:44 ` Tejun Heo
2012-08-03 21:41 ` Sasha Levin
2012-08-03 21:48 ` Tejun Heo
2012-08-03 22:20 ` Sasha Levin
2012-08-03 22:23 ` Tejun Heo
2012-08-03 22:26 ` Sasha Levin
2012-08-03 22:29 ` Linus Torvalds
2012-08-03 22:36 ` Tejun Heo
2012-08-03 23:47 ` Linus Torvalds
2012-08-04 0:03 ` Sasha Levin
2012-08-04 0:05 ` Linus Torvalds
2012-08-04 0:33 ` Sasha Levin
2012-08-04 0:05 ` Tejun Heo [this message]
2012-08-03 17:39 ` Eric Dumazet
2012-08-03 14:23 ` [RFC v2 2/7] user_ns: use new hashtable implementation Sasha Levin
2012-08-05 0:58 ` Eric W. Biederman
2012-08-03 14:23 ` [RFC v2 3/7] mm,ksm: " Sasha Levin
2012-08-03 14:23 ` [RFC v2 4/7] workqueue: " Sasha Levin
2012-08-03 14:23 ` [RFC v2 5/7] mm/huge_memory: " Sasha Levin
2012-08-03 14:23 ` [RFC v2 6/7] tracepoint: " Sasha Levin
2012-08-05 0:36 ` Steven Rostedt
2012-08-05 16:31 ` Mathieu Desnoyers
2012-08-05 17:03 ` Sasha Levin
2012-08-05 17:12 ` Mathieu Desnoyers
2012-08-03 14:23 ` [RFC v2 7/7] net,9p: " Sasha Levin
2012-08-03 18:00 ` Eric Dumazet
2012-08-03 21:14 ` Sasha Levin
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