From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: [for-next][PATCH 06/24] tracing: Simplify the max length test when using the filtering temp buffer
Date: Sat, 26 Jun 2021 09:04:10 -0400 [thread overview]
Message-ID: <20210626130535.582288691@goodmis.org> (raw)
In-Reply-To: 20210626130404.033700863@goodmis.org
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
When filtering trace events, a temp buffer is used because the extra copy
from the temp buffer into the ring buffer is still faster than the direct
write into the ring buffer followed by a discard if the filter does not
match.
But the data that can be stored in the temp buffer is a PAGE_SIZE minus the
ring buffer event header. The calculation of that header size is complex,
but using the helper macro "struct_size()" can simplify it.
Link: https://lore.kernel.org/stable/CAHk-=whKbJkuVmzb0hD3N6q7veprUrSpiBHRxVY=AffWZPtxmg@mail.gmail.com/
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/trace.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2e592885a167..a0a84ff46ecd 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2735,8 +2735,10 @@ trace_event_buffer_lock_reserve(struct trace_buffer **current_rb,
(trace_file->flags & (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) &&
(entry = this_cpu_read(trace_buffered_event))) {
/* Try to use the per cpu buffer first */
+ int max_len = PAGE_SIZE - struct_size(entry, array, 1);
+
val = this_cpu_inc_return(trace_buffered_event_cnt);
- if ((len < (PAGE_SIZE - sizeof(*entry) - sizeof(entry->array[0]))) && val == 1) {
+ if (val == 1 && likely(len <= max_len)) {
trace_event_setup(entry, type, trace_ctx);
entry->array[0] = len;
return entry;
--
2.30.2
next prev parent reply other threads:[~2021-06-26 13:05 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-26 13:04 [for-next][PATCH 00/24] tracing: Last minute updates for 5.14 Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 01/24] bootconfig: Change array value to use child node Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 02/24] bootconfig: Support mixing a value and subkeys under a key Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 03/24] tools/bootconfig: Support mixed value and subkey test cases Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 04/24] docs: bootconfig: Update for mixing value and subkeys Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 05/24] bootconfig: Share the checksum function with tools Steven Rostedt
2021-06-26 13:04 ` Steven Rostedt [this message]
2021-06-26 13:04 ` [for-next][PATCH 07/24] tracing: Add better comments for the filtering temp buffer use case Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 08/24] tracing: Add tp_printk_stop_on_boot option Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 09/24] tracing: Have ftrace_dump_on_oops kernel parameter take numbers Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 10/24] bootconfig/tracing/ktest: Add ktest examples of testing bootconfig Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 11/24] trace/hwlat: Fix Clarks email Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 12/24] trace/hwlat: Implement the mode config option Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 13/24] trace/hwlat: Switch disable_migrate to mode none Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 14/24] trace/hwlat: Implement the per-cpu mode Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 15/24] trace: Add a generic function to read/write u64 values from tracefs Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 16/24] trace/hwlat: Use trace_min_max_param for width and window params Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 17/24] trace/hwlat: Remove printk from sampling loop Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 18/24] trace: Add __print_ns_to_secs() and __print_ns_without_secs() helpers Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 19/24] tracing: Add LATENCY_FS_NOTIFY to define if latency_fsnotify() is defined Steven Rostedt
2021-07-20 19:19 ` Arnd Bergmann
2021-06-26 13:04 ` [for-next][PATCH 20/24] trace: Add osnoise tracer Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 21/24] trace: Add timerlat tracer Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 22/24] trace/hwlat: Protect kdata->kthread with get/put_online_cpus Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 23/24] trace/hwlat: Support hotplug operations Steven Rostedt
2021-06-26 13:04 ` [for-next][PATCH 24/24] trace/osnoise: " Steven Rostedt
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