[dpdk-dev] [PATCH v4 1/2] mbuf: support attaching external buffer to mbuf

[Yongseok Koh]

> On Apr 25, 2018, at 2:08 AM, Yongseok Koh <yskoh at mellanox.com> wrote:
>> On Apr 25, 2018, at 1:28 AM, Olivier Matz <olivier.matz at 6wind.com> wrote:
>> 
>> Hi Yongseok,
>> 
>> On Tue, Apr 24, 2018 at 06:02:44PM +0200, Olivier Matz wrote:
>>>>> @@ -688,14 +704,33 @@ rte_mbuf_to_baddr(struct rte_mbuf *md)
>>>>> }
>>>>> /**
>>>>> + * Returns TRUE if given mbuf is cloned by mbuf indirection, or FALSE
>>>>> + * otherwise.
>>>>> + *
>>>>> + * If a mbuf has its data in another mbuf and references it by mbuf
>>>>> + * indirection, this mbuf can be defined as a cloned mbuf.
>>>>> + */
>>>>> +#define RTE_MBUF_CLONED(mb)     ((mb)->ol_flags & IND_ATTACHED_MBUF)
>>>>> +
>>>>> +/**
>>>>>  * Returns TRUE if given mbuf is indirect, or FALSE otherwise.
>>>>>  */
>>>>> -#define RTE_MBUF_INDIRECT(mb)   ((mb)->ol_flags & IND_ATTACHED_MBUF)
>>>>> +#define RTE_MBUF_INDIRECT(mb)   RTE_MBUF_CLONED(mb)
>>>> 
>>>> It is still confusing that INDIRECT != !DIRECT.
>>>> May be we have no good options right now, but I'd suggest to at least
>>>> deprecate
>>>> RTE_MBUF_INDIRECT() and completely remove it in the next release.
>>> 
>>> Agree. I may have missed something, but is my previous suggestion
>>> not doable?
>>> 
>>> - direct = embeds its own data      (and indirect = !direct)
>>> - clone (or another name) = data is another mbuf
>>> - extbuf = data is in an external buffer
>> 
>> Any comment about this option?
> 
> I liked your idea, so I defined RTE_MBUF_CLONED() and wanted to deprecate
> RTE_MBUF_INDIRECT() in the coming release. But RTE_MBUF_DIRECT() can't be
> (!RTE_MBUF_INDIRECT()) because it will logically include RTE_MBUF_HAS_EXTBUF().
> I'm not sure I understand you correctly.
> 
> Can you please give me more guidelines so that I can take you idea?

Maybe, did you mean the following? Looks like doable but RTE_MBUF_DIRECT()
can't logically mean 'mbuf embeds its own data', right?

#define RTE_MBUF_INDIRECT(mb)   ((mb)->ol_flags & IND_ATTACHED_MBUF)
#define RTE_MBUF_DIRECT(mb)     (!RTE_MBUF_INDIRECT(mb))

#define RTE_MBUF_HAS_EXTBUF(mb) ((mb)->ol_flags & EXT_ATTACHED_MBUF)
#define RTE_MBUF_CLONED(mb)     ((mb)->ol_flags & IND_ATTACHED_MBUF)

[...]

@@ -1327,7 +1572,7 @@ rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
 
        if (likely(rte_mbuf_refcnt_read(m) == 1)) {
 
-               if (RTE_MBUF_INDIRECT(m))
+               if (RTE_MBUF_INDIRECT(m) || RTE_MBUF_HAS_EXTBUF(m))
                        rte_pktmbuf_detach(m);
 
                if (m->next != NULL) {
@@ -1339,7 +1584,7 @@ rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
 
        } else if (__rte_mbuf_refcnt_update(m, -1) == 0) {
 
-               if (RTE_MBUF_INDIRECT(m))
+               if (RTE_MBUF_INDIRECT(m) || RTE_MBUF_HAS_EXTBUF(m))
                        rte_pktmbuf_detach(m);
 
                if (m->next != NULL) {


Thanks,
Yongseok