22/07/2022 17:14, Morten Brørup пишет:
From: Huichao Cai [mailto:chcch...@163.com]
Sent: Friday, 22 July 2022 17.59
At 2022-07-22 23:52:28, "Morten Brørup" <m...@smartsharesystems.com> wrote:
From: Stephen Hemminger [mailto:step...@networkplumber.org]
Sent: Friday, 22 July 2022 16.49
On Fri, 22 Jul 2022 21:01:50 +0800
Huichao Cai <chcch...@163.com> wrote:
Some NIC drivers support MBUF_FAST_FREE(Device supports optimization
for fast release of mbufs. When set application must guarantee that
per-queue all mbufs comes from the same mempool and has refcnt = 1)
offload. In order to adapt to this offload function, add this API.
Add some test data for this API.
Signed-off-by: Huichao Cai <chcch...@163.com>
The code should just be checking that refcnt == 1 directly.
There are cases where sender passes a cloned mbuf. This is independent
of the fast free optimization.
Similar to what Linux kernel does with skb_cow().
Olivier just confirmed that MBUF_FAST_FREE requires that the mbufs are direct
and non-segmented, although these requirements are not yet documented.
This means that you should not generate segmented mbufs with this patch. I
don't know what to do instead; probably fail with an appropriate errno.
When the bnxt driver sends mbuf, it will take the mbuf segments apart and hang
it to the tx_buf_ring, so there is no mbuf segments when it is released. Does
this mean that there can be mbuf segments?
Only if the bnxt driver also resets the segmentation fields (nb_segs and next)
in those mbufs, which I suppose it does, if it supports MBUF_FAST_FREE with
segmented packets.
However, other Ethernet drivers don't do that, so a generic library function
cannot rely on it. These missing requirements for MBUF_FAST_FREE is a bug,
either in the MBUF_FAST_FREE documentation, or in the drivers where
MBUF_FAST_FREE only works correctly with direct and non-segmented mbufs.
I believe multi-segment packets work ok with MBUF_FAST_FREE
(as long as other requirements are met).
