On 04/25/2018 02:34 AM, Yongseok Koh wrote:
On Tue, Apr 24, 2018 at 09:15:38PM +0200, Olivier Matz wrote:
On Tue, Apr 24, 2018 at 09:21:00PM +0300, Andrew Rybchenko wrote:
On 04/24/2018 07:02 PM, Olivier Matz wrote:
+ m->ol_flags |= EXT_ATTACHED_MBUF;
+ m->shinfo = shinfo;
+
+ rte_mbuf_ext_refcnt_set(shinfo, 1);
Why is assignment used here? Cannot we attach extbuf already attached to
other mbuf?
In rte_pktmbuf_attach(), this is true. That's not illogical to
keep the same approach here. Maybe an assert could be added?
Like I described in the doc, intention is to attach external buffer by
_attach_extbuf() for the first time and _attach() is just for additional mbuf
attachment. Will add an assert.
Not sure that I understand. How should the second chunk with shared shinfo
of the huge buffer be attached to a new mbuf?
Other option is to have shinfo per small buf plus reference counter
per huge buf (which is decremented when small buf reference counter
becomes zero and free callback is executed). I guess it is assumed above.
My fear is that it is too much reference counters:
1. mbuf reference counter
2. small buf reference counter
3. huge buf reference counter
May be it is possible use (1) for (2) as well?
I would prefer to have only 2 reference counters, one in the mbuf
and one in the shinfo.
Good discussion. It should be a design decision by user.
In my use-case, it would be a good idea to make all the mbufs in a same chunk
point to the same shared info in the head of the chunk and reset the refcnt of
shinfo to the total number of slices in the chunk.
+--+----+----+--------------+----+--------------+---+- - -
|global |head|mbuf1 data |head|mbuf2 data | |
| shinfo|room| |room| | |
+--+----+----+--------------+----+--------------+---+- - -
I don't understand how it can be achieved using proposed API.
Andrew.
