[PATCH 06/16] blktrace: only calculate trace length once
From: Johannes Thumshirn <hidden>
Date: 2025-09-09 11:06:47
Also in:
linux-trace-kernel, lkml
Subsystem:
block layer, the rest, tracing · Maintainers:
Jens Axboe, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
De-duplicate the calculation of the trace length instead of doing the calculation twice, once for calling trace_buffer_lock_reserve() and once for calling relay_reserve(). Signed-off-by: Johannes Thumshirn <redacted> --- kernel/trace/blktrace.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 5db0c1a4ef5e..d06519957c25 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c@@ -104,13 +104,14 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action, int cpu = smp_processor_id(); bool blk_tracer = blk_tracer_enabled; ssize_t cgid_len = cgid ? sizeof(cgid) : 0; + size_t trace_len; + trace_len = sizeof(*t) + cgid_len + len; if (blk_tracer) { buffer = blk_tr->array_buffer.buffer; trace_ctx = tracing_gen_ctx_flags(0); event = trace_buffer_lock_reserve(buffer, TRACE_BLK, - sizeof(*t) + len + cgid_len, - trace_ctx); + trace_len, trace_ctx); if (!event) return; t = ring_buffer_event_data(event);
@@ -125,7 +126,7 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action, if (!bt->rchan) return; - t = relay_reserve(bt->rchan, sizeof(*t) + len + cgid_len); + t = relay_reserve(bt->rchan, trace_len); if (t) { t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION; t->time = ktime_to_ns(ktime_get());
@@ -254,6 +255,7 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes, bool blk_tracer = blk_tracer_enabled; ssize_t cgid_len = cgid ? sizeof(cgid) : 0; const enum req_op op = opf & REQ_OP_MASK; + size_t trace_len; if (unlikely(bt->trace_state != Blktrace_running && !blk_tracer)) return;
@@ -276,14 +278,14 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes, return; cpu = raw_smp_processor_id(); + trace_len = sizeof(*t) + pdu_len + cgid_len; if (blk_tracer) { tracing_record_cmdline(current); buffer = blk_tr->array_buffer.buffer; trace_ctx = tracing_gen_ctx_flags(0); event = trace_buffer_lock_reserve(buffer, TRACE_BLK, - sizeof(*t) + pdu_len + cgid_len, - trace_ctx); + trace_len, trace_ctx); if (!event) return; t = ring_buffer_event_data(event);
@@ -304,7 +306,7 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes, * from coming in and stepping on our toes. */ local_irq_save(flags); - t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len + cgid_len); + t = relay_reserve(bt->rchan, trace_len); if (t) { sequence = per_cpu_ptr(bt->sequence, cpu);
--
2.51.0