[PATCH] iommu/arm-smmu-v3: add tracepoints for cmdq_issue_cmdlist
Jean-Philippe Brucker
jean-philippe at linaro.org
Fri Aug 28 03:41:07 EDT 2020
Hi,
On Thu, Aug 27, 2020 at 09:33:51PM +1200, Barry Song wrote:
> cmdq_issue_cmdlist() is the hotspot that uses a lot of time. This patch
> adds tracepoints for it to help debug.
>
> Signed-off-by: Barry Song <song.bao.hua at hisilicon.com>
> ---
> * can furthermore develop an eBPF program to benchmark using this trace
Have you tried using kprobe and kretprobe instead of tracepoints?
Any noticeable performance drop?
Thanks,
Jean
>
> cmdlistlat.c:
> #include <uapi/linux/ptrace.h>
>
> BPF_HASH(start, u32);
> BPF_HISTOGRAM(dist);
>
> TRACEPOINT_PROBE(arm_smmu_v3, issue_cmdlist_entry)
> {
> u32 pid;
> u64 ts, *val;
>
> pid = bpf_get_current_pid_tgid();
> ts = bpf_ktime_get_ns();
> start.update(&pid, &ts);
> return 0;
> }
>
> TRACEPOINT_PROBE(arm_smmu_v3, issue_cmdlist_exit)
> {
> u32 pid;
> u64 *tsp, delta;
>
> pid = bpf_get_current_pid_tgid();
> tsp = start.lookup(&pid);
>
> if (tsp != 0) {
> delta = bpf_ktime_get_ns() - *tsp;
> dist.increment(bpf_log2l(delta));
> start.delete(&pid);
> }
>
> return 0;
> }
>
> cmdlistlat.py:
> #!/usr/bin/python3
> #
> from __future__ import print_function
> from bcc import BPF
> from ctypes import c_ushort, c_int, c_ulonglong
> from time import sleep
> from sys import argv
>
> def usage():
> print("USAGE: %s [interval [count]]" % argv[0])
> exit()
>
> # arguments
> interval = 5
> count = -1
> if len(argv) > 1:
> try:
> interval = int(argv[1])
> if interval == 0:
> raise
> if len(argv) > 2:
> count = int(argv[2])
> except: # also catches -h, --help
> usage()
>
> # load BPF program
> b = BPF(src_file = "cmdlistlat.c")
>
> # header
> print("Tracing... Hit Ctrl-C to end.")
>
> # output
> loop = 0
> do_exit = 0
> while (1):
> if count > 0:
> loop += 1
> if loop > count:
> exit()
> try:
> sleep(interval)
> except KeyboardInterrupt:
> pass; do_exit = 1
>
> print()
> b["dist"].print_log2_hist("nsecs")
> b["dist"].clear()
> if do_exit:
> exit()
>
>
> drivers/iommu/arm/arm-smmu-v3/Makefile | 1 +
> .../iommu/arm/arm-smmu-v3/arm-smmu-v3-trace.h | 48 +++++++++++++++++++
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++++
> 3 files changed, 57 insertions(+)
> create mode 100644 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-trace.h
>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/Makefile b/drivers/iommu/arm/arm-smmu-v3/Makefile
> index 569e24e9f162..dba1087f91f3 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/Makefile
> +++ b/drivers/iommu/arm/arm-smmu-v3/Makefile
> @@ -1,2 +1,3 @@
> # SPDX-License-Identifier: GPL-2.0
> +ccflags-y += -I$(src) # needed for trace events
> obj-$(CONFIG_ARM_SMMU_V3) += arm-smmu-v3.o
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-trace.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-trace.h
> new file mode 100644
> index 000000000000..29ab96706124
> --- /dev/null
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-trace.h
> @@ -0,0 +1,48 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2020 Hisilicon Limited.
> + */
> +
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM arm_smmu_v3
> +
> +#if !defined(_ARM_SMMU_V3_TRACE_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _ARM_SMMU_V3_TRACE_H
> +
> +#include <linux/tracepoint.h>
> +
> +struct device;
> +
> +DECLARE_EVENT_CLASS(issue_cmdlist_class,
> + TP_PROTO(struct device *dev, int n, bool sync),
> + TP_ARGS(dev, n, sync),
> +
> + TP_STRUCT__entry(
> + __string(device, dev_name(dev))
> + __field(int, n)
> + __field(bool, sync)
> + ),
> + TP_fast_assign(
> + __assign_str(device, dev_name(dev));
> + __entry->n = n;
> + __entry->sync = sync;
> + ),
> + TP_printk("%s cmd number=%d sync=%d",
> + __get_str(device), __entry->n, __entry->sync)
> +);
> +
> +#define DEFINE_ISSUE_CMDLIST_EVENT(name) \
> +DEFINE_EVENT(issue_cmdlist_class, name, \
> + TP_PROTO(struct device *dev, int n, bool sync), \
> + TP_ARGS(dev, n, sync))
> +
> +DEFINE_ISSUE_CMDLIST_EVENT(issue_cmdlist_entry);
> +DEFINE_ISSUE_CMDLIST_EVENT(issue_cmdlist_exit);
> +
> +#endif /* _ARM_SMMU_V3_TRACE_H */
> +
> +#undef TRACE_INCLUDE_PATH
> +#undef TRACE_INCLUDE_FILE
> +#define TRACE_INCLUDE_PATH .
> +#define TRACE_INCLUDE_FILE arm-smmu-v3-trace
> +#include <trace/define_trace.h>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index 7332251dd8cd..e2d7d5f1d234 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -33,6 +33,8 @@
>
> #include <linux/amba/bus.h>
>
> +#include "arm-smmu-v3-trace.h"
> +
> /* MMIO registers */
> #define ARM_SMMU_IDR0 0x0
> #define IDR0_ST_LVL GENMASK(28, 27)
> @@ -1389,6 +1391,8 @@ static int arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu,
> }, head = llq;
> int ret = 0;
>
> + trace_issue_cmdlist_entry(smmu->dev, n, sync);
> +
> /* 1. Allocate some space in the queue */
> local_irq_save(flags);
> llq.val = READ_ONCE(cmdq->q.llq.val);
> @@ -1493,6 +1497,7 @@ static int arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu,
> }
>
> local_irq_restore(flags);
> + trace_issue_cmdlist_exit(smmu->dev, n, sync);
> return ret;
> }
>
> @@ -4166,6 +4171,9 @@ static struct platform_driver arm_smmu_driver = {
> };
> module_platform_driver(arm_smmu_driver);
>
> +#define CREATE_TRACE_POINTS
> +#include "arm-smmu-v3-trace.h"
> +
> MODULE_DESCRIPTION("IOMMU API for ARM architected SMMUv3 implementations");
> MODULE_AUTHOR("Will Deacon <will at kernel.org>");
> MODULE_ALIAS("platform:arm-smmu-v3");
> --
> 2.27.0
>
>
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