afb81b8278
Some checks failed
Docker. / Ubuntu (push) Has been cancelled
User-agent updater. / User-agent (push) Failing after 15s
Lock Threads / lock (push) Failing after 10s
Waiting for answer. / waiting-for-answer (push) Failing after 22s
Needs user action. / needs-user-action (push) Failing after 8s
Can't reproduce. / cant-reproduce (push) Failing after 8s
Close stale issues and PRs / stale (push) Has been cancelled
60 lines
1.7 KiB
Groff
60 lines
1.7 KiB
Groff
.\" Copyright (c) 2008-2009 Apple Inc. All rights reserved.
|
|
.Dd May 1, 2009
|
|
.Dt dispatch_benchmark 3
|
|
.Os Darwin
|
|
.Sh NAME
|
|
.Nm dispatch_benchmark
|
|
.Nd Measures block execution time
|
|
.Sh SYNOPSIS
|
|
.Fd #include <dispatch/dispatch.h>
|
|
.Ft uint64_t
|
|
.Fo dispatch_benchmark
|
|
.Fa "size_t count" "void (^block)(void)"
|
|
.Fc
|
|
.Ft uint64_t
|
|
.Fo dispatch_benchmark_f
|
|
.Fa "size_t count" "void *context" "void (*function)(void *)"
|
|
.Fc
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn dispatch_benchmark
|
|
function executes the given
|
|
.Fa block
|
|
multiple times according to the
|
|
.Fa count
|
|
variable and then returns the average number of nanoseconds per execution.
|
|
This function is for debugging and performance analysis work.
|
|
For the best
|
|
results, pass a high count value to
|
|
.Fn dispatch_benchmark .
|
|
When benchmarking concurrent code, please compare the
|
|
serial version of the code against the concurrent version, and compare the
|
|
concurrent version on different classes of hardware.
|
|
Please look for inflection
|
|
points with various data sets and keep the following facts in mind:
|
|
.Pp
|
|
.Bl -bullet -offset indent -compact
|
|
.It
|
|
Code bound by computational bandwidth may be inferred by proportional
|
|
changes in performance as concurrency is increased.
|
|
.It
|
|
Code bound by memory bandwidth may be inferred by negligible changes in
|
|
performance as concurrency is increased.
|
|
.It
|
|
Code bound by critical sections may be inferred by retrograde changes in
|
|
performance as concurrency is increased.
|
|
.Bl -bullet -offset indent -compact
|
|
.It
|
|
Intentional: locks, mutexes, and condition variables.
|
|
.It
|
|
Accidental: unrelated and frequently modified data on the same cache-line.
|
|
.El
|
|
.El
|
|
.Sh RETURN VALUE
|
|
The
|
|
.Fn dispatch_benchmark
|
|
function returns the average number of nanoseconds the given block takes to
|
|
execute.
|
|
.Sh SEE ALSO
|
|
.Xr dispatch 3
|