Date: Wed, 3 Jun 2009 18:12:17 -0700 From: Kip Macy <kmacy@freebsd.org> To: Robert Watson <rwatson@freebsd.org> Cc: src-committers@freebsd.org, svn-src-user@freebsd.org Subject: Re: svn commit: r193363 - user/kmacy/releng_7_2_fcs/sys/dev/cxgb Message-ID: <3c1674c90906031812r3d5940ffybc1144257359b18d@mail.gmail.com> In-Reply-To: <alpine.BSF.2.00.0906030829150.52806@fledge.watson.org> References: <200906030206.n5326nlY035216@svn.freebsd.org> <alpine.BSF.2.00.0906030829150.52806@fledge.watson.org>
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On Wed, Jun 3, 2009 at 12:30 AM, Robert Watson <rwatson@freebsd.org> wrote:
> On Wed, 3 Jun 2009, Kip Macy wrote:
>
>> clear next pointers and set M_PKTHDR when needed
>
> Without looking at the context in detail, in general, you need to allocate
> mbufs intended to be headers as that from inception, or use M_MOVE_PKTHDR().
> MAC, for example, allocates an mbuf tag with each PKTHDR mbuf so that
> there's always storage for the MAC label on a packet, and if you hand assign
> the M_PKTHDR flag to mbufs, that alloation will be missed. This is only a
> problem if you later inject that header into the stack, but that's usually
> the point of adding headers so I'm guessing that can happen here? :-)
The problem is that by doing that I end up taking cache misses on the
mbuf twice. How does MAC support deferred initialization? I can just
defer the actual mbuf allocation if need be.
-Kip
-Kip
>
> Robert N M Watson
> Computer Laboratory
> University of Cambridge
>
>>
>> Modified:
>> user/kmacy/releng_7_2_fcs/sys/dev/cxgb/cxgb_sge.c
>>
>> Modified: user/kmacy/releng_7_2_fcs/sys/dev/cxgb/cxgb_sge.c
>>
>> ==============================================================================
>> --- user/kmacy/releng_7_2_fcs/sys/dev/cxgb/cxgb_sge.c Wed Jun 3
>> 01:59:42 2009 (r193362)
>> +++ user/kmacy/releng_7_2_fcs/sys/dev/cxgb/cxgb_sge.c Wed Jun 3
>> 02:06:49 2009 (r193363)
>> @@ -2678,6 +2678,8 @@ get_packet(adapter_t *adap, unsigned int
>> flags = M_PKTHDR;
>> if (fl->zone != zone_pack)
>> m_cljset(m0, cl, fl->type);
>> + m0->m_flags |= flags;
>> + m0->m_next = m0->m_nextpkt = NULL;
>> m0->m_pkthdr.len = m0->m_len = len;
>> }
>> switch(sopeop) {
>>
>
--
When bad men combine, the good must associate; else they will fall one
by one, an unpitied sacrifice in a contemptible struggle.
Edmund Burke
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