Date: Sun, 11 Jul 2010 23:04:20 +1000 From: Lawrence Stewart <lstewart@freebsd.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r209119 - head/sys/sys Message-ID: <4C39C154.7090706@freebsd.org> In-Reply-To: <20100711082454.GN2408@deviant.kiev.zoral.com.ua> References: <201006130239.o5D2du3m086332@svn.freebsd.org> <20100613101025.GD1320@garage.freebsd.pl> <4C158B71.205@freebsd.org> <20100614085205.GD13238@deviant.kiev.zoral.com.ua> <4C1605A7.2000202@freebsd.org> <20100614104349.GF13238@deviant.kiev.zoral.com.ua> <4C198A90.3060905@freebsd.org> <20100617071300.GX13238@deviant.kiev.zoral.com.ua> <4C1AD292.5070508@freebsd.org> <4C369172.4020700@freebsd.org> <20100711082454.GN2408@deviant.kiev.zoral.com.ua>
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On 07/11/10 18:24, Kostik Belousov wrote:
> On Fri, Jul 09, 2010 at 01:03:14PM +1000, Lawrence Stewart wrote:
>> On 06/18/10 11:57, Lawrence Stewart wrote:
>>> On 06/17/10 17:13, Kostik Belousov wrote:
>>>> On Thu, Jun 17, 2010 at 12:38:08PM +1000, Lawrence Stewart wrote:
>>>>> On 06/14/10 20:43, Kostik Belousov wrote:
>>> [snip]
>>>>>> Or, you could ditch the sum at all, indeed using ({}) and returning the
>>>>>> result. __typeof is your friend to select proper type of accumulator.
>>>>>
>>>>> So, something like this?
>>>>>
>>>>> #define DPCPU_SUM(n, var) __extension__ \
>>>>> ({ \
>>>>> u_int
>>>>> _i; \
>>>>> __typeof((DPCPU_PTR(n))->var)
>>>>> sum; \
>>>>>
>>>>> \
>>>>> sum =
>>>>> 0; \
>>>>> CPU_FOREACH(_i)
>>>>> { \
>>>>> sum += (DPCPU_ID_PTR(_i,
>>>>> n))->var; \
>>>>>
>>>>> } \
>>>>>
>>>>> sum; \
>>>>> })
>>>>>
>>>>> Which can be used like this:
>>>>>
>>>>> totalss.n_in = DPCPU_SUM(ss, n_in);
>>
>> [snip]
>>
>>> I'll commit the above version of the macro this evening (GMT+10) unless
>>> I hear any objections. Thanks to all of you for your input.
>>
>> Any objections to the following patch going in as a follow up to the
>> above discussion?
>>
>> http://people.freebsd.org/~lstewart/patches/tcp_ffcaia2008/dpcpu_zeromember_9.x.r209745.patch
>>
>> Turns out I need DPCPU_ZERO to fix a bug in SIFTR and it occurred to me
>> that providing variants of the macros which work on the DPCPU variable
>> itself or a member of a DPCPU struct makes good sense. The new patch
>> therefore renames my original DPCPU_SUM to DPCPU_MEMBERSUM and includes
>> DPCPU_MEMBERZERO().
>>
>> Also open to suggestions on a sensible shortening of MEMBER or other
>> appropriate and descriptive indicator to reduce the macro name lengths.
>> MBR implies some sort of memory barrier... any other ideas?
>
> I suggest changing MEMBER to VAR.
I'd be happy with that. If I don't get a better suggestion or an
objection I'll go with DPCPU_VARZERO and DPCPU_VARSUM. Thanks for the input.
> Are the macros only believed to be useful, or you already use them ?
DPCPU_ZERO and DPCPU_MEMBERSUM I have an immediate use for in the SIFTR
code. I don't have an immediate use for DPCPU_MEMBERZERO and DPCPU_SUM,
but I can imagine they will both find use once people start converting
stats counters and various other kernel data to DPCPU.
> For the usual reasons, it seems to be better to wrap DCPU_ZERO
> into do/while (0).
Oops, good point. Will do.
Cheers,
Lawrence
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