diff mbox series

[bpf-next,v2,3/5] xsk: introduce padding between more ring pointers

Message ID 1605006094-31097-4-git-send-email-magnus.karlsson@gmail.com (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series xsk: i40e: Tx performance improvements | expand

Checks

Context Check Description
netdev/cover_letter success Link
netdev/fixes_present success Link
netdev/patch_count success Link
netdev/tree_selection success Clearly marked for bpf-next
netdev/subject_prefix success Link
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Link
netdev/module_param success Was 0 now: 0
netdev/build_32bit fail Errors and warnings before: 5 this patch: 5
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success Link
netdev/checkpatch fail Link
netdev/build_allmodconfig_warn success Errors and warnings before: 1 this patch: 1
netdev/header_inline success Link
netdev/stable success Stable not CCed

Commit Message

Magnus Karlsson Nov. 10, 2020, 11:01 a.m. UTC 
From: Magnus Karlsson <magnus.karlsson@intel.com>

Introduce one cache line worth of padding between the consumer pointer
and the flags field as well as between the flags field and the start
of the descriptors in all the lockless rings. This so that the x86 HW
adjacency prefetcher will not prefetch the adjacent pointer/field when
only one pointer/field is going to be used. This improves throughput
performance for the l2fwd sample app with 1% on my machine with HW
prefetching turned on in the BIOS.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
---
 net/xdp/xsk_queue.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index cdb9cf3..74fac80 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -18,9 +18,11 @@  struct xdp_ring {
 	/* Hinder the adjacent cache prefetcher to prefetch the consumer
 	 * pointer if the producer pointer is touched and vice versa.
 	 */
-	u32 pad ____cacheline_aligned_in_smp;
+	u32 pad1 ____cacheline_aligned_in_smp;
 	u32 consumer ____cacheline_aligned_in_smp;
+	u32 pad2 ____cacheline_aligned_in_smp;
 	u32 flags;
+	u32 pad3 ____cacheline_aligned_in_smp;
 };
 
 /* Used for the RX and TX queues for packets */