On Tue, 24 Jan 2017 19:57:13 +0400, Ilya Matveychikov
[off-list ref] wrote:

quoted

On Jan 24, 2017, at 4:56 PM, Olivier MATZ [off-list ref]
wrote:

Hi,

On Sat, 21 Jan 2017 16:28:29 +0000, "Ananyev, Konstantin"
[off-list ref] wrote:  

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-----Original Message-----
From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Ilya
Matveychikov Sent: Saturday, January 21, 2017 3:08 PM
To: Yigit, Ferruh <redacted>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] mbuf: remove redundant line in
rte_pktmbuf_attach

  

quoted

On Jan 20, 2017, at 4:08 PM, Ferruh Yigit
[off-list ref] wrote:

On 1/20/2017 12:19 AM, Ilya Matveychikov wrote:    

quoted

mi->next will be assigned to NULL few lines later, trivial patch

Signed-off-by: Ilya V. Matveychikov <redacted>
---
lib/librte_mbuf/rte_mbuf.h | 1 -
1 file changed, 1 deletion(-)

diff --git a/lib/librte_mbuf/rte_mbuf.h

b/lib/librte_mbuf/rte_mbuf.h index ead7c6e..5589d54 100644

--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h

@@ -1139,7 +1139,6 @@ static inline void

rte_pktmbuf_attach(struct rte_mbuf *mi, struct rte_mbuf *m)
mi->buf_addr = m->buf_addr; mi->buf_len = m->buf_len;

-	mi->next = m->next;    

Fixes: ea672a8b1655 ("mbuf: remove the rte_pktmbuf structure")

Acked-by: Olivier Matz <redacted>

  

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Do you know why attaching mbuf is not supporting
multi-segment?    

This is supported, but you have to do it segment by segment.
Actually  rte_pktmbuf_clone() does that.
Konstantin

  

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Perhaps this can be documented in function comment, as one of the
"not supported" items.    

No, I don’t know. For my application I’ve found that nb_segs with
it’s limit in 256 segments is very annoying and I’ve decided not
to use DPDK functions that dealt with nb_segs… But it is not
about the rte_pktmbuf_attach() function and the patch.   

Out of curiosity, can you explain why your application needs more
than 256 segments? When we were discussing the possibility of
extending this field to 16 bits, Konstantin convinced me that it
was not so useful.  

In my application I need to do IPv4 fragments reassembly. There is no
explicit limit of number of fragments in datagram, so I’m trying to
avoid any limitations and `nb_segs` here is a constraint for me.
Expanding it from 8-bit to 16-bit can solve that issue for me. But I
don’t remember are there any  other places in DPDK where we need to
know how many segments are in the packet? I mean that is `nb_segs`
required at all?

Yes, it is used for instance in some PMDs to know how many tx ring
descriptors are needed to send a packet.

Thank you for the explanation. As you probably seen, I'm proposing to
extend the nb_segs to 16 bits in my latest RFC patchset.

Regards,
Olivier