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Message-ID: <20241107161026.2903044-14-aleksander.lobakin@intel.com>
Date: Thu, 7 Nov 2024 17:10:20 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
Toke Høiland-Jørgensen <toke@...hat.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
John Fastabend <john.fastabend@...il.com>,
Andrii Nakryiko <andrii@...nel.org>,
Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
Stanislav Fomichev <sdf@...ichev.me>,
Magnus Karlsson <magnus.karlsson@...el.com>,
nex.sw.ncis.osdt.itp.upstreaming@...el.com,
bpf@...r.kernel.org,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH net-next v4 13/19] xsk: align &xdp_buff_xsk harder
After the series "XSk buff on a diet" by Maciej, the greatest pow-2
which &xdp_buff_xsk can be divided got reduced from 16 to 8 on x86_64.
Also, sizeof(xdp_buff_xsk) now is 120 bytes, which, taking the previous
sentence into account, leads to that it leaves 8 bytes at the end of
cacheline, which means an array of buffs will have its elements
messed between the cachelines chaotically.
Use __aligned_largest for this struct. This alignment is usually 16
bytes, which makes it fill two full cachelines and align an array
nicely. ___cacheline_aligned may be excessive here, especially on
arches with 128-256 byte CLs, as well as 32-bit arches (76 -> 96
bytes on MIPS32R2), while not doing better than _largest.
Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
---
include/net/xsk_buff_pool.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
index 3832997cc605..50779406bc2d 100644
--- a/include/net/xsk_buff_pool.h
+++ b/include/net/xsk_buff_pool.h
@@ -29,7 +29,7 @@ struct xdp_buff_xsk {
dma_addr_t frame_dma;
struct xsk_buff_pool *pool;
struct list_head list_node;
-};
+} __aligned_largest;
#define XSK_CHECK_PRIV_TYPE(t) BUILD_BUG_ON(sizeof(t) > offsetofend(struct xdp_buff_xsk, cb))
#define XSK_TX_COMPL_FITS(t) BUILD_BUG_ON(sizeof(struct xsk_tx_metadata_compl) > sizeof(t))
--
2.47.0
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