From: Christoph Lameter <cl@linux.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Tejun Heo <tj@kernel.org>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
rusty@rustcorp.com.au, tglx@linutronix.de, x86@kernel.org,
linux-kernel@vger.kernel.org, hpa@zytor.com,
Paul Mundt <lethal@linux-sh.org>,
rmk@arm.linux.org.uk, starvik@axis.com, ralf@linux-mips.org,
davem@davemloft.net, cooloney@kernel.org, kyle@mcmartin.ca,
matthew@wil.cx, grundler@parisc-linux.org, takata@linux-m32r.org,
benh@kernel.crashing.org, rth@twiddle.net,
ink@jurassic.park.msu.ru, heiko.carstens@de.ibm.com,
Nick Piggin <npiggin@suse.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH UPDATED] percpu: use dynamic percpu allocator as the default percpu allocator
Date: Mon, 13 Apr 2009 14:18:08 -0400 (EDT) [thread overview]
Message-ID: <alpine.DEB.1.10.0904131409510.13756@qirst.com> (raw)
In-Reply-To: <20090408162651.GA14449@elte.hu>
On Wed, 8 Apr 2009, Ingo Molnar wrote:
> Dude, this is a new facility freshly modernized and freshly made
> usable. What did you expect, for a thousand usecases pop up in the
> kernel overnight? _None_ of this code is "common" today per se. (the
> networking folks are working on making it more and more common
> though)
?? kfree(NULL) has been allowed for years. None of this is new.
> > Speculation. A shutdown fastpath? The percpu allocation and free
> > operations are expensive and deal with teardown and setup of
> > virtual mappings. Those paths are *not* optimized for fastpath
> > use. kfree is different.
>
> Of course a lot of this is speculation, dynamic percpu so far has
> been a rarely used facility compared to kmalloc()/kfree(). If you
> dont accept my analogy that's fine - but that is opinion against
> opinion - while you state you opinion as truism.
Please look at the kernel source for the use of percpu_free and
percpu_alloc.
> So my point remains: your patch had effects you clearly did not
> anticipate, and the cacheline alignment management situation is not
> nearly as clear-cut as you imagine it to be.
There was no effect that I did not anticipate. Just imagination on your
part that percpu_free is used like kfree.
Again: The frequent insertion of __read_mostly will
destroy the purpose and function of the read mostly areas!
> Unfortunately you failed to answer my detailed mail that made very
> specific points though, you only got into generalities and flames
> about my summary mail - so it's hard to judge what your opinion
> about those specific facts is - you have not stated one.
I was pretty clear on those points. Not sure what material question I did
not answer. What you say here fits your posts. Generalizing from kfree to
percpu_free etc...
next prev parent reply other threads:[~2009-04-13 18:28 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-10 7:53 [GIT RFC] percpu: use dynamic percpu allocator as the default percpu allocator Tejun Heo
2009-03-10 7:53 ` [PATCH 1/5] linker script: define __per_cpu_load on all SMP capable archs Tejun Heo
2009-03-10 7:53 ` [PATCH 2/5] percpu: make x86 addr <-> pcpu ptr conversion macros generic Tejun Heo
2009-03-10 7:53 ` [PATCH 3/5] percpu: more flexibility for @dyn_size of pcpu_setup_first_chunk() Tejun Heo
2009-03-10 7:53 ` [PATCH 4/5] percpu: generalize embedding first chunk setup helper Tejun Heo
2009-03-10 7:53 ` [PATCH 5/5] percpu: use dynamic percpu allocator as the default percpu allocator Tejun Heo
2009-03-10 7:57 ` test module to verify " Tejun Heo
2009-03-10 10:59 ` [GIT RFC] percpu: use dynamic percpu allocator as the default " David Miller
2009-03-11 6:03 ` Tejun Heo
2009-03-11 5:56 ` [GIT PULL] pull request for safe part Tejun Heo
2009-03-16 18:01 ` [GIT RFC] percpu: use dynamic percpu allocator as the default percpu allocator Martin Schwidefsky
2009-03-20 2:35 ` Tejun Heo
2009-03-24 15:22 ` Tejun Heo
2009-03-25 11:27 ` Martin Schwidefsky
2009-03-25 11:51 ` Tejun Heo
2009-03-25 12:22 ` Ingo Molnar
2009-03-25 12:27 ` Tejun Heo
2009-03-25 12:39 ` Ingo Molnar
2009-03-25 13:13 ` Martin Schwidefsky
2009-03-25 13:21 ` Tejun Heo
2009-03-25 13:25 ` Martin Schwidefsky
2009-03-25 13:34 ` Tejun Heo
2009-03-31 16:54 ` Martin Schwidefsky
2009-03-31 17:20 ` Christoph Lameter
2009-03-31 20:18 ` Martin Schwidefsky
2009-03-31 21:10 ` Christoph Lameter
2009-04-01 8:01 ` Martin Schwidefsky
2009-03-31 19:17 ` Ivan Kokshaysky
2009-03-31 20:19 ` Martin Schwidefsky
2009-03-31 20:29 ` Ivan Kokshaysky
2009-04-01 0:07 ` Tejun Heo
2009-04-01 8:10 ` Martin Schwidefsky
2009-04-01 8:17 ` Tejun Heo
2009-04-01 8:32 ` Martin Schwidefsky
2009-04-01 8:37 ` David Miller
2009-04-01 8:47 ` Martin Schwidefsky
2009-04-01 8:50 ` Tejun Heo
2009-04-01 9:08 ` Martin Schwidefsky
2009-04-02 1:54 ` Tejun Heo
2009-04-01 8:53 ` David Miller
2009-04-01 8:53 ` Tejun Heo
2009-04-01 11:07 ` Martin Schwidefsky
2009-04-02 1:57 ` Tejun Heo
2009-04-02 7:24 ` Ivan Kokshaysky
2009-04-02 11:13 ` Martin Schwidefsky
2009-04-03 0:31 ` Tejun Heo
2009-04-07 16:09 ` Ivan Kokshaysky
2009-04-08 20:18 ` Tejun Heo
2009-04-09 9:47 ` Ivan Kokshaysky
2009-04-09 11:53 ` Tejun Heo
2009-04-11 1:38 ` Rusty Russell
2009-04-11 1:52 ` Tejun Heo
2009-04-02 0:20 ` Rusty Russell
2009-03-25 14:00 ` Martin Schwidefsky
2009-03-25 14:14 ` Tejun Heo
2009-03-30 10:07 ` [PATCH UPDATED] " Tejun Heo
2009-03-30 10:42 ` Martin Schwidefsky
2009-04-01 0:08 ` Tejun Heo
2009-03-30 11:49 ` Ingo Molnar
2009-03-30 14:50 ` Christoph Lameter
2009-03-31 16:12 ` Christoph Lameter
2009-04-01 0:15 ` Tejun Heo
2009-04-01 13:49 ` Christoph Lameter
2009-04-01 15:49 ` Ingo Molnar
2009-04-01 18:06 ` Christoph Lameter
2009-04-01 19:01 ` Ingo Molnar
2009-04-01 19:39 ` Linus Torvalds
2009-04-01 20:12 ` Matthew Wilcox
2009-04-02 2:13 ` Ingo Molnar
2009-04-01 22:32 ` Ingo Molnar
2009-04-01 22:57 ` Matthew Wilcox
2009-04-02 2:10 ` Ingo Molnar
2009-04-02 2:21 ` Christoph Lameter
2009-04-02 3:25 ` Ingo Molnar
2009-04-02 3:28 ` Christoph Lameter
2009-04-02 2:30 ` Tejun Heo
2009-04-02 2:18 ` Christoph Lameter
2009-04-02 3:42 ` Ingo Molnar
2009-04-02 13:53 ` Christoph Lameter
2009-04-08 16:26 ` Ingo Molnar
2009-04-13 18:18 ` Christoph Lameter [this message]
2009-04-14 14:04 ` Ingo Molnar
2009-04-14 16:48 ` Christoph Lameter
2009-04-14 17:12 ` Ingo Molnar
2009-04-02 2:15 ` Christoph Lameter
2009-04-02 4:19 ` [PATCH 1/2 x86#core/percpu] percpu: don't put the first chunk in reverse-map rbtree Tejun Heo
2009-04-02 4:21 ` [PATCH 2/2 x86#core/percpu] percpu: remove rbtree and use page->index instead Tejun Heo
2009-04-08 17:03 ` [tip:core/percpu] " Christoph Lameter
2009-04-08 17:03 ` [tip:core/percpu] percpu: don't put the first chunk in reverse-map rbtree Tejun Heo
2009-03-31 16:14 ` [PATCH UPDATED] percpu: use dynamic percpu allocator as the default percpu allocator Christoph Lameter
2009-04-01 0:18 ` Tejun Heo
2009-03-31 1:34 ` Rusty Russell
2009-03-31 22:57 ` David Miller
2009-03-31 23:49 ` Benjamin Herrenschmidt
2009-04-01 0:19 ` Tejun Heo
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