From: Linus Torvalds <torvalds@linux-foundation.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Nick Piggin <npiggin@suse.de>, Jens Axboe <jens.axboe@oracle.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH 2/4] generic-smp: remove kmalloc usage
Date: Thu, 19 Feb 2009 08:52:03 -0800 (PST) [thread overview]
Message-ID: <alpine.LFD.2.00.0902190848570.21686@localhost.localdomain> (raw)
In-Reply-To: <200902191501.47564.rusty@rustcorp.com.au>
On Thu, 19 Feb 2009, Rusty Russell wrote:
>
> So if we care about the kmalloc, why didn't we see benchmarks when we
> switched from the x86 smp_call_function_mask to the generic one? Or did
> I just miss them (there's nothing in the git commit).
I don't think we care about kmalloc from a performance angle. Sure, it's
nice if we can make IPI's be really low cost, and we should aim for that,
but the reason the kmalloc() was added was never performance - nor is that
the reason we now try to remove it.
The kmalloc() was added for correctness reasons, and we now try to remove
it to make the code look saner and simpler (and hopefully it gets faster
too, but I don't think that was ever a primary issue), since we ended up
having _three_ different cases for the whole insane memory allocation
(on-stack, per-cpu and kmalloc), and nobody sane really wants that.
Linus
next prev parent reply other threads:[~2009-02-19 16:54 UTC|newest]
Thread overview: 101+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-16 16:38 [PATCH 0/4] generic smp helpers vs kmalloc Peter Zijlstra
2009-02-16 16:38 ` [PATCH 1/4] generic-smp: remove single ipi fallback for smp_call_function_many() Peter Zijlstra
2009-02-16 19:10 ` Oleg Nesterov
2009-02-16 19:41 ` Peter Zijlstra
2009-02-16 20:30 ` Oleg Nesterov
2009-02-16 20:55 ` Peter Zijlstra
2009-02-16 21:22 ` Oleg Nesterov
2009-02-17 12:25 ` Oleg Nesterov
2009-02-16 20:49 ` Q: smp.c && barriers (Was: [PATCH 1/4] generic-smp: remove single ipi fallback for smp_call_function_many()) Oleg Nesterov
2009-02-16 21:03 ` Peter Zijlstra
2009-02-16 21:32 ` Oleg Nesterov
2009-02-16 21:45 ` Peter Zijlstra
2009-02-16 22:02 ` Oleg Nesterov
2009-02-16 22:24 ` Peter Zijlstra
2009-02-16 23:19 ` Oleg Nesterov
2009-02-17 9:29 ` Peter Zijlstra
2009-02-17 10:11 ` Nick Piggin
2009-02-17 10:27 ` Peter Zijlstra
2009-02-17 10:39 ` Nick Piggin
2009-02-17 11:26 ` Nick Piggin
2009-02-17 11:48 ` Peter Zijlstra
2009-02-17 15:51 ` Paul E. McKenney
2009-02-18 2:15 ` Suresh Siddha
2009-02-18 2:40 ` Paul E. McKenney
2009-02-17 19:28 ` Q: " Oleg Nesterov
2009-02-17 21:32 ` Paul E. McKenney
2009-02-17 21:45 ` Oleg Nesterov
2009-02-17 22:39 ` Paul E. McKenney
2009-02-18 13:52 ` Nick Piggin
2009-02-18 16:09 ` Linus Torvalds
2009-02-18 16:21 ` Ingo Molnar
2009-02-18 16:33 ` Linus Torvalds
2009-02-18 16:58 ` Ingo Molnar
2009-02-18 17:05 ` Ingo Molnar
2009-02-18 17:10 ` Ingo Molnar
2009-02-18 17:17 ` Linus Torvalds
2009-02-18 17:23 ` Ingo Molnar
2009-02-18 17:14 ` Linus Torvalds
2009-02-18 17:47 ` Ingo Molnar
2009-02-18 18:33 ` Suresh Siddha
2009-02-18 16:37 ` Gleb Natapov
2009-02-19 0:12 ` Nick Piggin
2009-02-19 6:47 ` Benjamin Herrenschmidt
2009-02-19 13:11 ` Nick Piggin
2009-02-19 15:06 ` Ingo Molnar
2009-02-19 21:49 ` Benjamin Herrenschmidt
2009-02-18 2:21 ` Suresh Siddha
2009-02-18 13:59 ` Nick Piggin
2009-02-18 16:19 ` Linus Torvalds
2009-02-18 16:23 ` Ingo Molnar
2009-02-18 18:43 ` Suresh Siddha
2009-02-18 19:17 ` Ingo Molnar
2009-02-18 23:55 ` Suresh Siddha
2009-02-19 12:20 ` Ingo Molnar
2009-02-19 12:29 ` Nick Piggin
2009-02-19 12:45 ` Ingo Molnar
2009-02-19 22:00 ` Suresh Siddha
2009-02-20 10:56 ` Ingo Molnar
2009-02-20 18:56 ` Suresh Siddha
2009-02-20 19:40 ` Ingo Molnar
2009-02-20 23:28 ` Jack Steiner
2009-02-25 3:32 ` Nick Piggin
2009-02-25 12:47 ` Ingo Molnar
2009-02-25 18:25 ` Luck, Tony
2009-03-17 18:16 ` Suresh Siddha
2009-03-18 8:51 ` [tip:x86/x2apic] x86: add x2apic_wrmsr_fence() to x2apic flush tlb paths Suresh Siddha
2009-02-17 12:40 ` Q: smp.c && barriers (Was: [PATCH 1/4] generic-smp: remove single ipi fallback for smp_call_function_many()) Peter Zijlstra
2009-02-17 15:43 ` Paul E. McKenney
2009-02-17 15:40 ` [PATCH] generic-smp: remove kmalloc() Peter Zijlstra
2009-02-17 17:21 ` Oleg Nesterov
2009-02-17 17:40 ` Peter Zijlstra
2009-02-17 17:46 ` Peter Zijlstra
2009-02-17 18:30 ` Oleg Nesterov
2009-02-17 19:29 ` [PATCH -v4] generic-ipi: " Peter Zijlstra
2009-02-17 20:02 ` Oleg Nesterov
2009-02-17 20:11 ` Peter Zijlstra
2009-02-17 20:16 ` Peter Zijlstra
2009-02-17 20:44 ` Oleg Nesterov
2009-02-17 20:49 ` Peter Zijlstra
2009-02-17 22:09 ` Oleg Nesterov
2009-02-17 22:15 ` Peter Zijlstra
2009-02-17 21:30 ` Paul E. McKenney
2009-02-17 21:38 ` Peter Zijlstra
2009-02-16 16:38 ` [PATCH 2/4] generic-smp: remove kmalloc usage Peter Zijlstra
2009-02-17 0:40 ` Linus Torvalds
2009-02-17 8:24 ` Peter Zijlstra
2009-02-17 9:43 ` Ingo Molnar
2009-02-17 9:49 ` Peter Zijlstra
2009-02-17 10:56 ` Ingo Molnar
2009-02-18 4:50 ` Rusty Russell
2009-02-18 16:05 ` Ingo Molnar
2009-02-19 0:00 ` Jeremy Fitzhardinge
2009-02-19 12:21 ` Ingo Molnar
2009-02-19 4:31 ` Rusty Russell
2009-02-19 9:10 ` Peter Zijlstra
2009-02-19 11:04 ` Jens Axboe
2009-02-19 16:52 ` Linus Torvalds [this message]
2009-02-17 15:44 ` Linus Torvalds
2009-02-16 16:38 ` [PATCH 3/4] generic-smp: properly allocate the cpumasks Peter Zijlstra
2009-02-16 23:17 ` Rusty Russell
2009-02-16 16:38 ` [PATCH 4/4] generic-smp: clean up some of the csd->flags fiddling Peter Zijlstra
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