linux-kernel - Re: [RFC PATCH 7/8] [SCTP]: uninline sctp_add_cmd

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Message-ID: <47BD9872.9050308@hp.com>
Date:	Thu, 21 Feb 2008 10:27:46 -0500
From:	Vlad Yasevich <vladislav.yasevich@...com>
To:	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
Cc:	Netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [RFC PATCH 7/8] [SCTP]: uninline sctp_add_cmd_sf

Ilpo Järvinen wrote:
> On Wed, 20 Feb 2008, Vlad Yasevich wrote:
> 
>> Ilpo Järvinen wrote:
>>> I added inline to sctp_add_cmd and appropriate comment there to
>>> avoid adding another call into the call chain. This works at least
>>> with "gcc (GCC) 4.1.2 20070626 (Red Hat 4.1.2-13)". Alternatively,
>>> __sctp_add_cmd could be introduced to .h.
>>>
>> My only concern was performance regressions, but it looks like it
>> doesn't effect anything from the few quick runs I've made.
> 
> There was one call made anyway, it's a bit hard to see how it would hurt 
> to push that BUG() deeper down (in fact, this is one of the easiest case 
> in this respect, many other cases elsewhere that need uninlining don't 
> currently make any calls with inlines).
> 
>> Since we are putting sctp_add_cmd_sf() on the call stack, we might
>> as well get rid of sctp_add_cmd() and reduce it a bit more.
> 
> IMHO it is definately better solution for archiving the size reduction,
> I just didn't know before that the only sctp_add_cmd call could be 
> converted.

That one was a really silly one.  The chance of not calling BUG() in
that one case was so small, that it didn't really make any sense from
the code robustness side.

> 
> [...snip...]
>> diff --git a/net/sctp/command.c b/net/sctp/command.c
>> index bb97733..3a06513 100644
>> --- a/net/sctp/command.c
>> +++ b/net/sctp/command.c
>> @@ -51,19 +51,16 @@ int sctp_init_cmd_seq(sctp_cmd_seq_t *seq)
>>  
>>  /* Add a command to a sctp_cmd_seq_t.
>>   * Return 0 if the command sequence is full.
>> + *
>> + * Inline here is not a mistake, this way sctp_add_cmd_sf doesn't need extra
>> + * calls, size penalty is of insignificant magnitude here
> 
> This won't be a necessary note anymore. :-)
> 
> [...snip...]
> 

Yeah.  If you are going to resubmit, feel free to put my Signed-off-by line.

-vlad
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