* [PATCH v2 01/19] tracepoint: Add trace_call__##name() API
2026-03-23 16:00 [PATCH v2 00/19] tracepoint: Avoid double static_branch evaluation at guarded call sites Vineeth Pillai (Google)
@ 2026-03-23 16:00 ` Vineeth Pillai (Google)
2026-03-26 1:28 ` Masami Hiramatsu
2026-03-23 16:00 ` [PATCH v2 14/19] scsi: ufs: Use trace_call__##name() at guarded tracepoint call sites Vineeth Pillai (Google)
2026-03-24 14:28 ` [PATCH v2 00/19] tracepoint: Avoid double static_branch evaluation at guarded " Steven Rostedt
2 siblings, 1 reply; 5+ messages in thread
From: Vineeth Pillai (Google) @ 2026-03-23 16:00 UTC (permalink / raw)
To: Steven Rostedt, Peter Zijlstra, Dmitry Ilvokhin
Cc: Vineeth Pillai (Google), Masami Hiramatsu, Mathieu Desnoyers,
Ingo Molnar, Jens Axboe, io-uring, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, Alexei Starovoitov, Daniel Borkmann,
Marcelo Ricardo Leitner, Xin Long, Jon Maloy, Aaron Conole,
Eelco Chaudron, Ilya Maximets, netdev, bpf, linux-sctp,
tipc-discussion, dev, Jiri Pirko, Oded Gabbay, Koby Elbaz,
dri-devel, Rafael J. Wysocki, Viresh Kumar, Gautham R. Shenoy,
Huang Rui, Mario Limonciello, Len Brown, Srinivas Pandruvada,
linux-pm, MyungJoo Ham, Kyungmin Park, Chanwoo Choi,
Christian König, Sumit Semwal, linaro-mm-sig, Eddie James,
Andrew Jeffery, Joel Stanley, linux-fsi, David Airlie,
Simona Vetter, Alex Deucher, Danilo Krummrich, Matthew Brost,
Philipp Stanner, Harry Wentland, Leo Li, amd-gfx, Jiri Kosina,
Benjamin Tissoires, linux-input, Wolfram Sang, linux-i2c,
Mark Brown, Michael Hennerich, Nuno Sá, linux-spi,
James E.J. Bottomley, Martin K. Petersen, linux-scsi, Chris Mason,
David Sterba, linux-btrfs, Thomas Gleixner, Andrew Morton,
SeongJae Park, linux-mm, Borislav Petkov, Dave Hansen, x86,
linux-trace-kernel, linux-kernel
Add trace_call__##name() as a companion to trace_##name(). When a
caller already guards a tracepoint with an explicit enabled check:
if (trace_foo_enabled() && cond)
trace_foo(args);
trace_foo() internally repeats the static_branch_unlikely() test, which
the compiler cannot fold since static branches are patched binary
instructions. This results in two static-branch evaluations for every
guarded call site.
trace_call__##name() calls __do_trace_##name() directly, skipping the
redundant static-branch re-check. This avoids leaking the internal
__do_trace_##name() symbol into call sites while still eliminating the
double evaluation:
if (trace_foo_enabled() && cond)
trace_invoke_foo(args); /* calls __do_trace_foo() directly */
Three locations are updated:
- __DECLARE_TRACE: invoke form omits static_branch_unlikely, retains
the LOCKDEP RCU-watching assertion.
- __DECLARE_TRACE_SYSCALL: same, plus retains might_fault().
- !TRACEPOINTS_ENABLED stub: empty no-op so callers compile cleanly
when tracepoints are compiled out.
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Vineeth Pillai (Google) <vineeth@bitbyteword.org>
Assisted-by: Claude:claude-sonnet-4-6
---
include/linux/tracepoint.h | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 22ca1c8b54f32..ed969705341f1 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -294,6 +294,10 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
WARN_ONCE(!rcu_is_watching(), \
"RCU not watching for tracepoint"); \
} \
+ } \
+ static inline void trace_call__##name(proto) \
+ { \
+ __do_trace_##name(args); \
}
#define __DECLARE_TRACE_SYSCALL(name, proto, args, data_proto) \
@@ -313,6 +317,11 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
WARN_ONCE(!rcu_is_watching(), \
"RCU not watching for tracepoint"); \
} \
+ } \
+ static inline void trace_call__##name(proto) \
+ { \
+ might_fault(); \
+ __do_trace_##name(args); \
}
/*
@@ -398,6 +407,8 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
#define __DECLARE_TRACE_COMMON(name, proto, args, data_proto) \
static inline void trace_##name(proto) \
{ } \
+ static inline void trace_call__##name(proto) \
+ { } \
static inline int \
register_trace_##name(void (*probe)(data_proto), \
void *data) \
--
2.53.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH v2 01/19] tracepoint: Add trace_call__##name() API
2026-03-23 16:00 ` [PATCH v2 01/19] tracepoint: Add trace_call__##name() API Vineeth Pillai (Google)
@ 2026-03-26 1:28 ` Masami Hiramatsu
0 siblings, 0 replies; 5+ messages in thread
From: Masami Hiramatsu @ 2026-03-26 1:28 UTC (permalink / raw)
To: Vineeth Pillai (Google)
Cc: Steven Rostedt, Peter Zijlstra, Dmitry Ilvokhin, Masami Hiramatsu,
Mathieu Desnoyers, Ingo Molnar, Jens Axboe, io-uring,
David S. Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni,
Alexei Starovoitov, Daniel Borkmann, Marcelo Ricardo Leitner,
Xin Long, Jon Maloy, Aaron Conole, Eelco Chaudron, Ilya Maximets,
netdev, bpf, linux-sctp, tipc-discussion, dev, Jiri Pirko,
Oded Gabbay, Koby Elbaz, dri-devel, Rafael J. Wysocki,
Viresh Kumar, Gautham R. Shenoy, Huang Rui, Mario Limonciello,
Len Brown, Srinivas Pandruvada, linux-pm, MyungJoo Ham,
Kyungmin Park, Chanwoo Choi, Christian König, Sumit Semwal,
linaro-mm-sig, Eddie James, Andrew Jeffery, Joel Stanley,
linux-fsi, David Airlie, Simona Vetter, Alex Deucher,
Danilo Krummrich, Matthew Brost, Philipp Stanner, Harry Wentland,
Leo Li, amd-gfx, Jiri Kosina, Benjamin Tissoires, linux-input,
Wolfram Sang, linux-i2c, Mark Brown, Michael Hennerich,
Nuno Sá, linux-spi, James E.J. Bottomley, Martin K. Petersen,
linux-scsi, Chris Mason, David Sterba, linux-btrfs,
Thomas Gleixner, Andrew Morton, SeongJae Park, linux-mm,
Borislav Petkov, Dave Hansen, x86, linux-trace-kernel,
linux-kernel
On Mon, 23 Mar 2026 12:00:20 -0400
"Vineeth Pillai (Google)" <vineeth@bitbyteword.org> wrote:
> Add trace_call__##name() as a companion to trace_##name(). When a
> caller already guards a tracepoint with an explicit enabled check:
>
> if (trace_foo_enabled() && cond)
> trace_foo(args);
>
> trace_foo() internally repeats the static_branch_unlikely() test, which
> the compiler cannot fold since static branches are patched binary
> instructions. This results in two static-branch evaluations for every
> guarded call site.
>
> trace_call__##name() calls __do_trace_##name() directly, skipping the
> redundant static-branch re-check. This avoids leaking the internal
> __do_trace_##name() symbol into call sites while still eliminating the
> double evaluation:
>
> if (trace_foo_enabled() && cond)
> trace_invoke_foo(args); /* calls __do_trace_foo() directly */
nit: trace_call_foo() instead of trace_invoke_foo()?
Anyway looks good to me.
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
> Three locations are updated:
> - __DECLARE_TRACE: invoke form omits static_branch_unlikely, retains
> the LOCKDEP RCU-watching assertion.
> - __DECLARE_TRACE_SYSCALL: same, plus retains might_fault().
> - !TRACEPOINTS_ENABLED stub: empty no-op so callers compile cleanly
> when tracepoints are compiled out.
>
> Suggested-by: Steven Rostedt <rostedt@goodmis.org>
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Vineeth Pillai (Google) <vineeth@bitbyteword.org>
> Assisted-by: Claude:claude-sonnet-4-6
> ---
> include/linux/tracepoint.h | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index 22ca1c8b54f32..ed969705341f1 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -294,6 +294,10 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
> WARN_ONCE(!rcu_is_watching(), \
> "RCU not watching for tracepoint"); \
> } \
> + } \
> + static inline void trace_call__##name(proto) \
> + { \
> + __do_trace_##name(args); \
> }
>
> #define __DECLARE_TRACE_SYSCALL(name, proto, args, data_proto) \
> @@ -313,6 +317,11 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
> WARN_ONCE(!rcu_is_watching(), \
> "RCU not watching for tracepoint"); \
> } \
> + } \
> + static inline void trace_call__##name(proto) \
> + { \
> + might_fault(); \
> + __do_trace_##name(args); \
> }
>
> /*
> @@ -398,6 +407,8 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
> #define __DECLARE_TRACE_COMMON(name, proto, args, data_proto) \
> static inline void trace_##name(proto) \
> { } \
> + static inline void trace_call__##name(proto) \
> + { } \
> static inline int \
> register_trace_##name(void (*probe)(data_proto), \
> void *data) \
> --
> 2.53.0
>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v2 14/19] scsi: ufs: Use trace_call__##name() at guarded tracepoint call sites
2026-03-23 16:00 [PATCH v2 00/19] tracepoint: Avoid double static_branch evaluation at guarded call sites Vineeth Pillai (Google)
2026-03-23 16:00 ` [PATCH v2 01/19] tracepoint: Add trace_call__##name() API Vineeth Pillai (Google)
@ 2026-03-23 16:00 ` Vineeth Pillai (Google)
2026-03-24 14:28 ` [PATCH v2 00/19] tracepoint: Avoid double static_branch evaluation at guarded " Steven Rostedt
2 siblings, 0 replies; 5+ messages in thread
From: Vineeth Pillai (Google) @ 2026-03-23 16:00 UTC (permalink / raw)
Cc: Vineeth Pillai (Google), Steven Rostedt, Peter Zijlstra,
Alim Akhtar, Avri Altman, Bart Van Assche, James E.J. Bottomley,
Martin K. Petersen, Peter Wang, Bean Huo, Adrian Hunter,
Bao D. Nguyen, linux-scsi, linux-kernel, linux-trace-kernel
Replace trace_foo() with the new trace_call__foo() at sites already
guarded by trace_foo_enabled(), avoiding a redundant
static_branch_unlikely() re-evaluation inside the tracepoint.
trace_call__foo() calls the tracepoint callbacks directly without
utilizing the static branch again.
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Vineeth Pillai (Google) <vineeth@bitbyteword.org>
Assisted-by: Claude:claude-sonnet-4-6
---
drivers/ufs/core/ufshcd.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 899e663fea6e8..b27bde8ea7555 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -422,7 +422,7 @@ static void ufshcd_add_cmd_upiu_trace(struct ufs_hba *hba,
else
header = &lrb->ucd_rsp_ptr->header;
- trace_ufshcd_upiu(hba, str_t, header, &rq->sc.cdb,
+ trace_call__ufshcd_upiu(hba, str_t, header, &rq->sc.cdb,
UFS_TSF_CDB);
}
@@ -433,7 +433,7 @@ static void ufshcd_add_query_upiu_trace(struct ufs_hba *hba,
if (!trace_ufshcd_upiu_enabled())
return;
- trace_ufshcd_upiu(hba, str_t, &rq_rsp->header,
+ trace_call__ufshcd_upiu(hba, str_t, &rq_rsp->header,
&rq_rsp->qr, UFS_TSF_OSF);
}
@@ -446,12 +446,12 @@ static void ufshcd_add_tm_upiu_trace(struct ufs_hba *hba, unsigned int tag,
return;
if (str_t == UFS_TM_SEND)
- trace_ufshcd_upiu(hba, str_t,
+ trace_call__ufshcd_upiu(hba, str_t,
&descp->upiu_req.req_header,
&descp->upiu_req.input_param1,
UFS_TSF_TM_INPUT);
else
- trace_ufshcd_upiu(hba, str_t,
+ trace_call__ufshcd_upiu(hba, str_t,
&descp->upiu_rsp.rsp_header,
&descp->upiu_rsp.output_param1,
UFS_TSF_TM_OUTPUT);
@@ -471,7 +471,7 @@ static void ufshcd_add_uic_command_trace(struct ufs_hba *hba,
else
cmd = ufshcd_readl(hba, REG_UIC_COMMAND);
- trace_ufshcd_uic_command(hba, str_t, cmd,
+ trace_call__ufshcd_uic_command(hba, str_t, cmd,
ufshcd_readl(hba, REG_UIC_COMMAND_ARG_1),
ufshcd_readl(hba, REG_UIC_COMMAND_ARG_2),
ufshcd_readl(hba, REG_UIC_COMMAND_ARG_3));
@@ -523,7 +523,7 @@ static void ufshcd_add_command_trace(struct ufs_hba *hba, struct scsi_cmnd *cmd,
} else {
doorbell = ufshcd_readl(hba, REG_UTP_TRANSFER_REQ_DOOR_BELL);
}
- trace_ufshcd_command(cmd->device, hba, str_t, tag, doorbell, hwq_id,
+ trace_call__ufshcd_command(cmd->device, hba, str_t, tag, doorbell, hwq_id,
transfer_len, intr, lba, opcode, group_id);
}
--
2.53.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH v2 00/19] tracepoint: Avoid double static_branch evaluation at guarded call sites
2026-03-23 16:00 [PATCH v2 00/19] tracepoint: Avoid double static_branch evaluation at guarded call sites Vineeth Pillai (Google)
2026-03-23 16:00 ` [PATCH v2 01/19] tracepoint: Add trace_call__##name() API Vineeth Pillai (Google)
2026-03-23 16:00 ` [PATCH v2 14/19] scsi: ufs: Use trace_call__##name() at guarded tracepoint call sites Vineeth Pillai (Google)
@ 2026-03-24 14:28 ` Steven Rostedt
2 siblings, 0 replies; 5+ messages in thread
From: Steven Rostedt @ 2026-03-24 14:28 UTC (permalink / raw)
To: Vineeth Pillai (Google)
Cc: Peter Zijlstra, Dmitry Ilvokhin, Masami Hiramatsu,
Mathieu Desnoyers, Ingo Molnar, Jens Axboe, io-uring,
David S. Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni,
Alexei Starovoitov, Daniel Borkmann, Marcelo Ricardo Leitner,
Xin Long, Jon Maloy, Aaron Conole, Eelco Chaudron, Ilya Maximets,
netdev, bpf, linux-sctp, tipc-discussion, dev, Jiri Pirko,
Oded Gabbay, Koby Elbaz, dri-devel, Rafael J. Wysocki,
Viresh Kumar, Gautham R. Shenoy, Huang Rui, Mario Limonciello,
Len Brown, Srinivas Pandruvada, linux-pm, MyungJoo Ham,
Kyungmin Park, Chanwoo Choi, Christian König, Sumit Semwal,
linaro-mm-sig, Eddie James, Andrew Jeffery, Joel Stanley,
linux-fsi, David Airlie, Simona Vetter, Alex Deucher,
Danilo Krummrich, Matthew Brost, Philipp Stanner, Harry Wentland,
Leo Li, amd-gfx, Jiri Kosina, Benjamin Tissoires, linux-input,
Wolfram Sang, linux-i2c, Mark Brown, Michael Hennerich,
Nuno Sá, linux-spi, James E.J. Bottomley, Martin K. Petersen,
linux-scsi, Chris Mason, David Sterba, linux-btrfs,
Thomas Gleixner, Andrew Morton, SeongJae Park, linux-mm,
Borislav Petkov, Dave Hansen, x86, linux-trace-kernel,
linux-kernel
On Mon, 23 Mar 2026 12:00:19 -0400
"Vineeth Pillai (Google)" <vineeth@bitbyteword.org> wrote:
> When a caller already guards a tracepoint with an explicit enabled check:
>
> if (trace_foo_enabled() && cond)
> trace_foo(args);
Thanks Vineeth!
I'm going to start pulling in this series. I'll take the first patch, and
then any patch that has an Acked-by or Reviewed-by from the maintainer.
For patches without acks, I'll leave alone and then after the first patch
gets merged into mainline, the maintainers could pull in their own patches
at their own convenience. Unless of course they speak up now if they want
me to take them ;-)
-- Steve
^ permalink raw reply [flat|nested] 5+ messages in thread