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When running workloads heavy unbalanced towards TX (high TX, low RX traffic), sfc driver can retain the CPU during too long times. Although in many cases this is not enough to be visible, it can affect performance and system responsiveness. A way to reproduce it is to use a debug kernel and run some parallel netperf TX tests. In some systems, this will lead to this message being logged: kernel:watchdog: BUG: soft lockup - CPU#12 stuck for 22s! The reason is that sfc driver doesn't account any NAPI budget for the TX completion events work. With high-TX/low-RX traffic, this makes that the CPU is held for long time for NAPI poll. Documentations says "drivers can process completions for any number of Tx packets but should only process up to budget number of Rx packets". However, many drivers do limit the amount of TX completions that they process in a single NAPI poll. In the same way, this patch adds a limit for the TX work in sfc. With the patch applied, the watchdog warning never appears. Tested with netperf in different combinations: single process / parallel processes, TCP / UDP and different sizes of UDP messages. Repeated the tests before and after the patch, without any noticeable difference in network or CPU performance. Test hardware: Intel(R) Xeon(R) CPU E5-1620 v4 @ 3.50GHz (4 cores, 2 threads/core) Solarflare Communications XtremeScale X2522-25G Network Adapter Fixes:5227ecccea("sfc: remove tx and MCDI handling from NAPI budget consideration") Fixes:d19a537218("sfc_ef100: TX path for EF100 NICs") Reported-by: Fei Liu <feliu@redhat.com> Signed-off-by: Íñigo Huguet <ihuguet@redhat.com> Acked-by: Martin Habets <habetsm.xilinx@gmail.com> Link: https://lore.kernel.org/r/20230615084929.10506-1-ihuguet@redhat.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
46 lines
1.7 KiB
C
46 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/****************************************************************************
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* Driver for Solarflare network controllers and boards
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* Copyright 2018 Solarflare Communications Inc.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published
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* by the Free Software Foundation, incorporated herein by reference.
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*/
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#ifndef EFX_TX_COMMON_H
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#define EFX_TX_COMMON_H
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int efx_probe_tx_queue(struct efx_tx_queue *tx_queue);
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void efx_init_tx_queue(struct efx_tx_queue *tx_queue);
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void efx_fini_tx_queue(struct efx_tx_queue *tx_queue);
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void efx_remove_tx_queue(struct efx_tx_queue *tx_queue);
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void efx_dequeue_buffer(struct efx_tx_queue *tx_queue,
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struct efx_tx_buffer *buffer,
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unsigned int *pkts_compl,
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unsigned int *bytes_compl,
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unsigned int *efv_pkts_compl);
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static inline bool efx_tx_buffer_in_use(struct efx_tx_buffer *buffer)
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{
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return buffer->len || (buffer->flags & EFX_TX_BUF_OPTION);
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}
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void efx_xmit_done_check_empty(struct efx_tx_queue *tx_queue);
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int efx_xmit_done(struct efx_tx_queue *tx_queue, unsigned int index);
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void efx_enqueue_unwind(struct efx_tx_queue *tx_queue,
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unsigned int insert_count);
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struct efx_tx_buffer *efx_tx_map_chunk(struct efx_tx_queue *tx_queue,
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dma_addr_t dma_addr, size_t len);
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int efx_tx_tso_header_length(struct sk_buff *skb);
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int efx_tx_map_data(struct efx_tx_queue *tx_queue, struct sk_buff *skb,
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unsigned int segment_count);
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unsigned int efx_tx_max_skb_descs(struct efx_nic *efx);
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int efx_tx_tso_fallback(struct efx_tx_queue *tx_queue, struct sk_buff *skb);
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extern bool efx_separate_tx_channels;
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#endif
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