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From: Eric Dumazet <dada1@cosmosbay.com>
To: Pekka Paalanen <pq@iki.fi>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] x86 mmiotrace: fix relay-buffer-full flag for SMP
Date: Tue, 05 Feb 2008 22:35:24 +0100	[thread overview]
Message-ID: <47A8D69C.8010505@cosmosbay.com> (raw)
In-Reply-To: <20080205231452.16cc2f88@daedalus.pq.iki.fi>

Pekka Paalanen a écrit :
> On Tue, 05 Feb 2008 21:44:07 +0100
> Eric Dumazet <dada1@cosmosbay.com> wrote:
> 
>> Pekka Paalanen a écrit :
>>> diff --git a/arch/x86/kernel/mmiotrace/mmio-mod.c b/arch/x86/kernel/mmiotrace/mmio-mod.c
>>> index 82ae920..f492b65 100644
>>> --- a/arch/x86/kernel/mmiotrace/mmio-mod.c
>>> +++ b/arch/x86/kernel/mmiotrace/mmio-mod.c
>>> @@ -47,9 +48,13 @@ struct trap_reason {
>>>  	int active_traces;
>>>  };
>>>  
>>> +/* Accessed per-cpu. */
>>>  static struct trap_reason pf_reason[NR_CPUS];
>>>  static struct mm_io_header_rw cpu_trace[NR_CPUS];
>>>  
>>> +/* Access to this is not per-cpu. */
>>> +static atomic_t dropped[NR_CPUS];
>>> +
>> Please dont introduce NR_CPUS new arrays, since people are working hard to zap 
>> them from kernel.
>>
>> You probably can use a per_cpu variable ?
> 
> Yes, it would probably be more appropriate to use DEFINE_PER_CPU()
> for 'pf_reason' and 'cpu_trace', but I wasn't sure since the examples
> of DEFINE_PER_CPU I saw always had integers or pointers, not
> whole structs. Is it okay for whole structs?

yes you can use a structure, you can check for example :

net/ipv4/route.c:static DEFINE_PER_CPU(struct rt_cache_stat, rt_cache_stat);

> 
> 'dropped' on the other hand is not accessed in per-cpu style, any cpu
> may access any element. DEFINE_PER_CPU is not valid here, is it?

It is valid, you can use per_cpu() accessor to get a pointer to a particular 
cpu data.

check net/ipv4/route.c for an example :

return &per_cpu(rt_cache_stat, cpu);


  reply	other threads:[~2008-02-05 21:45 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-27 16:52 [PATCH] x86: Add a list for custom page fault handlers Pekka Paalanen
2008-01-27 17:55 ` [RFC PATCH] x86: mmiotrace - trace memory mapped IO Pekka Paalanen
2008-01-30 22:39   ` Pekka Paalanen
2008-01-27 19:29 ` [PATCH] x86: Add a list for custom page fault handlers Ingo Molnar
2008-01-27 21:03 ` Peter Zijlstra
2008-01-30  2:28 ` Harvey Harrison
2008-01-30  2:34   ` Harvey Harrison
2008-01-30 18:08     ` Pekka Paalanen
2008-01-31 15:07       ` Ingo Molnar
2008-01-31 16:02         ` [PATCH v2] " Pekka Paalanen
2008-01-31 16:15           ` Arjan van de Ven
2008-02-03  6:55             ` Pekka Paalanen
2008-02-03  7:03               ` Ingo Molnar
2008-02-03 21:40                 ` Pekka Paalanen
2008-02-05 20:28                 ` [PATCH 1/4] x86 mmiotrace: use lookup_address() Pekka Paalanen
2008-02-05 20:30                   ` [PATCH 2/4] x86 mmiotrace: fix relay-buffer-full flag for SMP Pekka Paalanen
2008-02-05 20:44                     ` Eric Dumazet
2008-02-05 21:14                       ` Pekka Paalanen
2008-02-05 21:35                         ` Eric Dumazet [this message]
2008-02-09 17:53                           ` [PATCH] x86 mmiotrace: Use percpu instead of arrays Pekka Paalanen
2008-02-05 20:31                   ` [PATCH 3/4] x86 mmiotrace: comment about user space ABI Pekka Paalanen
2008-02-05 20:39                   ` [PATCH 4/4] x86 mmiotrace: move files into arch/x86/mm/ Pekka Paalanen
2008-02-06  3:02                     ` Randy Dunlap
2008-02-09 11:21                       ` Pekka Paalanen
2008-02-07 12:53                     ` Ingo Molnar
2008-02-07 12:56                       ` Christoph Hellwig
2008-02-09 17:52                         ` [RFC PATCH] x86: explicit call to mmiotrace in do_page_fault() Pekka Paalanen
2008-02-09 18:01                           ` Arjan van de Ven
2008-02-09 18:23                             ` Pekka Paalanen
2008-02-09 18:56                               ` Pekka Enberg
2008-02-09 19:11                                 ` Pekka Paalanen
2008-02-09 19:19                                   ` Pekka Enberg
2008-02-09 18:39                             ` Peter Zijlstra
2008-02-09 18:39                           ` Peter Zijlstra
2008-02-10 18:05                             ` [RFC PATCH v2] " Pekka Paalanen
2008-02-11  2:12                               ` Pavel Roskin
2008-02-11 18:04                                 ` Pekka Paalanen
2008-02-06  5:00                   ` [PATCH 1/4] x86 mmiotrace: use lookup_address() Christoph Hellwig
2008-02-07 12:52                     ` Ingo Molnar
2008-01-31 16:16           ` [RFC PATCH v2] x86: mmiotrace - trace memory mapped IO Pekka Paalanen
2008-01-31 16:29             ` Arjan van de Ven
2008-02-03  7:21               ` Pekka Paalanen
2008-01-30 18:20 ` [PATCH] x86: Add a list for custom page fault handlers Arjan van de Ven

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