From: Li Zefan <lizf@cn.fujitsu.com>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@elte.hu>,
Frederic Weisbecker <fweisbec@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: event tracing, ringbuffer and RB_MAX_SMALL_DATA
Date: Thu, 16 Jul 2009 08:48:42 +0800 [thread overview]
Message-ID: <4A5E78EA.60903@cn.fujitsu.com> (raw)
In-Reply-To: <1247651305.14973.3.camel@johannes.local>
Johannes Berg wrote:
> On Wed, 2009-07-15 at 09:08 +0800, Li Zefan wrote:
>
>> Right, the length of a dynamic array is not recorded, and this
>> causes 2 problems:
>>
>> - the event filter is not working properly for dynamic strings
>> - userspace parsers can't figure out the length of those arrays
>>
>> I had an idea some time ago, and hopefully will send out a
>> patch today or tomorrow.
>
> Well except for the corner case I pointed out, you can determine the
> length of dynamic arrays by either
> - the next dynamic array's offset or
> - the length of the item.
>
> So, afaict, the simplest solution would be to not embed the length of
> the item in type_len if it's not divisible by four and contains dynamic
> members, though the latter condition might be hard to check.
>
Actually I'm going to encode the size of a dynamic array
in it's @offset, so the lower 16bits is offset and the
higher 16bits is size.
next prev parent reply other threads:[~2009-07-16 0:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-14 17:18 event tracing, ringbuffer and RB_MAX_SMALL_DATA Johannes Berg
2009-07-15 1:08 ` Li Zefan
2009-07-15 9:48 ` Johannes Berg
2009-07-16 0:48 ` Li Zefan [this message]
2009-07-21 1:25 ` Steven Rostedt
2009-07-21 1:30 ` Li Zefan
2009-07-21 1:42 ` Steven Rostedt
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