Re: [PATCH v2 net-next 1/9] xdp: introduce mb in xdp_buff/xdp_frame
From: Alexei Starovoitov <hidden>
Date: 2020-09-04 01:07:11
Also in:
bpf
On Thu, Sep 03, 2020 at 10:58:45PM +0200, Lorenzo Bianconi wrote:
quoted hunk ↗ jump to hunk
Introduce multi-buffer bit (mb) in xdp_frame/xdp_buffer to specify if shared_info area has been properly initialized for non-linear xdp buffers Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org> --- include/net/xdp.h | 8 ++++++-- net/core/xdp.c | 1 + 2 files changed, 7 insertions(+), 2 deletions(-)diff --git a/include/net/xdp.h b/include/net/xdp.h index 3814fb631d52..42f439f9fcda 100644 --- a/include/net/xdp.h +++ b/include/net/xdp.h@@ -72,7 +72,8 @@ struct xdp_buff { void *data_hard_start; struct xdp_rxq_info *rxq; struct xdp_txq_info *txq; - u32 frame_sz; /* frame size to deduce data_hard_end/reserved tailroom*/ + u32 frame_sz:31; /* frame size to deduce data_hard_end/reserved tailroom*/ + u32 mb:1; /* xdp non-linear buffer */ }; /* Reserve memory area at end-of data area.@@ -96,7 +97,8 @@ struct xdp_frame { u16 len; u16 headroom; u32 metasize:8; - u32 frame_sz:24; + u32 frame_sz:23; + u32 mb:1; /* xdp non-linear frame */
Hmm. Last time I checked compilers were generating ugly code with bitfields. Not performant and not efficient. frame_sz is used in the fast path. I suspect the first hunk alone will cause performance degradation. Could you use normal u8 or u32 flag field?