From: Tejun Heo <tj@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>,
Eric Dumazet <eric.dumazet@gmail.com>,
linux-kernel@vger.kernel.org, mingo@elte.hu, paulus@samba.org,
davem@davemloft.net, fweisbec@gmail.com,
perfmon2-devel@lists.sf.net, eranian@gmail.com,
robert.richter@amd.com, acme@redhat.com
Subject: Re: [RFC PATCH 1/2] perf_events: add support for per-cpu per-cgroup monitoring (v3)
Date: Fri, 10 Sep 2010 10:41:27 +0200 [thread overview]
Message-ID: <4C89EF37.5080803@kernel.org> (raw)
In-Reply-To: <1284106566.402.26.camel@laptop>
Hello,
On 09/10/2010 10:16 AM, Peter Zijlstra wrote:
> On Thu, 2010-09-09 at 23:41 +0200, Stephane Eranian wrote:
>>> alloc_percpu() is zalloc_percpu() in fact, memory is already cleared.
>>>
>> I remember thinking about this and trying to trace to the code down
>> to figure this out. But it is rather complicated. If alloc_percpu() always
>> clears the memory, then I think that calling is zalloc_percpu()
>> would be more helpful....
Maybe but at this point it might be a bit too late. The allocator has
been that way since the beginning.
> pcpu_populate_chunk() in mm/percpu-vm.c does indeed do that memset, the
> one in mm/percpu-km.c does not.
>
> It is not obviously clear to me the -km allocator does indeed result in
> zero filled memory.
Nice catch. Fortunately, the -km allocator isn't currently being used
in upstrea although it was enabled for linux-next a couple of days
ago. I'll fix it up.
Thank you.
--
tejun
next prev parent reply other threads:[~2010-09-10 8:42 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-09 13:09 [RFC PATCH 1/2] perf_events: add support for per-cpu per-cgroup monitoring (v3) Stephane Eranian
2010-09-09 13:52 ` Eric Dumazet
2010-09-09 21:41 ` Stephane Eranian
2010-09-10 8:16 ` Peter Zijlstra
2010-09-10 8:41 ` Tejun Heo [this message]
2010-09-10 8:52 ` [PATCH percpu#for-next] percpu: clear memory allocated with the km allocator Tejun Heo
2010-09-10 8:55 ` Peter Zijlstra
2010-09-10 16:31 ` Randy Dunlap
2010-09-10 16:45 ` Ingo Molnar
2010-09-10 23:28 ` Tejun Heo
2010-09-10 8:59 ` [RFC PATCH 1/2] perf_events: add support for per-cpu per-cgroup monitoring (v3) Stephane Eranian
2010-09-10 9:03 ` [PATCH] percpu: update comments to reflect that percpu allocations are always zero-filled Tejun Heo
2010-09-10 9:07 ` Stephane Eranian
2010-09-10 9:09 ` Eric Dumazet
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