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From: Magnus Karlsson <magnus.karlsson@intel.com>
To: magnus.karlsson@intel.com, bjorn.topel@intel.com, ast@kernel.org,
	daniel@iogearbox.net, netdev@vger.kernel.org,
	jonathan.lemon@gmail.com
Cc: bpf@vger.kernel.org, saeedm@mellanox.com,
	jeffrey.t.kirsher@intel.com, maciej.fijalkowski@intel.com,
	maciejromanfijalkowski@gmail.com
Subject: [PATCH bpf-next 01/12] xsk: eliminate the lazy update threshold
Date: Mon,  9 Dec 2019 08:56:18 +0100	[thread overview]
Message-ID: <1575878189-31860-2-git-send-email-magnus.karlsson@intel.com> (raw)
In-Reply-To: <1575878189-31860-1-git-send-email-magnus.karlsson@intel.com>

The lazy update threshold was introduced to keep the producer and
consumer some distance apart in the completion ring. This was
important in the beginning of the development of AF_XDP as the ring
format as that point in time was very sensitive to the producer and
consumer being on the same cache line. This is not the case
anymore as the current ring format does not degrade in any noticeable
way when this happens. Moreover, this threshold makes it impossible
to run the system with rings that have less than 128 entries.

So let us remove this threshold and just get one entry from the ring
as in all other functions. This will enable us to remove this function
in a later commit. Note that xskq_produce_addr_lazy followed by
xskq_produce_flush_addr_n are still not the same function as
xskq_produce_addr() as it operates on another cached pointer.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
---
 net/xdp/xsk_queue.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index eddae46..a2f0ba6 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -11,7 +11,6 @@
 #include <net/xdp_sock.h>
 
 #define RX_BATCH_SIZE 16
-#define LAZY_UPDATE_THRESHOLD 128
 
 struct xdp_ring {
 	u32 producer ____cacheline_aligned_in_smp;
@@ -239,7 +238,7 @@ static inline int xskq_produce_addr_lazy(struct xsk_queue *q, u64 addr)
 {
 	struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
 
-	if (xskq_nb_free(q, q->prod_head, LAZY_UPDATE_THRESHOLD) == 0)
+	if (xskq_nb_free(q, q->prod_head, 1) == 0)
 		return -ENOSPC;
 
 	/* A, matches D */
-- 
2.7.4


  reply	other threads:[~2019-12-09  7:56 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-09  7:56 [PATCH bpf-next 00/12] xsk: clean up ring access functions Magnus Karlsson
2019-12-09  7:56 ` Magnus Karlsson [this message]
2019-12-09  7:56 ` [PATCH bpf-next 02/12] xsk: consolidate to one single cached producer pointer Magnus Karlsson
2019-12-10  0:42   ` Martin Lau
2019-12-10  9:04     ` Magnus Karlsson
2019-12-13 18:04   ` Maxim Mikityanskiy
2019-12-16  8:46     ` Magnus Karlsson
2019-12-19 14:35       ` Maxim Mikityanskiy
2019-12-19 16:21         ` Magnus Karlsson
2019-12-09  7:56 ` [PATCH bpf-next 03/12] xsk: standardize naming of producer ring access functions Magnus Karlsson
2019-12-09  7:56 ` [PATCH bpf-next 04/12] xsk: simplify detection of empty and full rings Magnus Karlsson
2019-12-09  7:56 ` [PATCH bpf-next 05/12] xsk: eliminate the RX batch size Magnus Karlsson
2019-12-09 10:16   ` Sergei Shtylyov
2019-12-09 13:07     ` Magnus Karlsson
2019-12-09  7:56 ` [PATCH bpf-next 06/12] xsk: simplify xskq_nb_avail and xskq_nb_free Magnus Karlsson
2019-12-09  7:56 ` [PATCH bpf-next 07/12] xsk: simplify the consumer ring access functions Magnus Karlsson
2019-12-09  7:56 ` [PATCH bpf-next 08/12] xsk: change names of validation functions Magnus Karlsson
2019-12-09  7:56 ` [PATCH bpf-next 09/12] xsk: ixgbe: i40e: ice: mlx5: xsk_umem_discard_addr to xsk_umem_release_addr Magnus Karlsson
2019-12-09  7:56 ` [PATCH bpf-next 10/12] xsk: remove unnecessary READ_ONCE of data Magnus Karlsson
2019-12-09  7:56 ` [PATCH bpf-next 11/12] xsk: add function naming comments and reorder functions Magnus Karlsson
2019-12-09  7:56 ` [PATCH bpf-next 12/12] xsk: use struct_size() helper Magnus Karlsson
2019-12-10  1:02 ` [PATCH bpf-next 00/12] xsk: clean up ring access functions Martin Lau

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