Messages in this thread Patches in this message | | | Subject | Re: [PATCH v3 2/3] perf bench syscall: Add close syscall benchmark | From | Tiezhu Yang <> | Date | Wed, 26 Oct 2022 12:37:42 +0800 |
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On 10/25/2022 11:37 PM, Ian Rogers wrote: > On Thu, Oct 6, 2022 at 12:42 AM Tiezhu Yang <yangtiezhu@loongson.cn> wrote: >> >> This commit adds a simple close syscall benchmark, more syscall >> benchmarks can be added in the future. >>
...
>> diff --git a/tools/perf/bench/syscall.c b/tools/perf/bench/syscall.c >> index 746fd71..058394b 100644 >> --- a/tools/perf/bench/syscall.c >> +++ b/tools/perf/bench/syscall.c >> @@ -46,6 +46,9 @@ static int bench_syscall_common(int argc, const char **argv, int syscall) >> case __NR_getppid: >> getppid(); >> break; >> + case __NR_close: >> + close(dup(0)); > > Thanks for contributing! This benchmark will compute the cost of close > and dup, naively dup could perform memory allocation and be slow. > Perhaps a number of file descriptors could be made outside of the > timed region? >
Hi Ian,
Thanks for your review and suggestion.
I tried the following changes based on this patchset, it shows "dup failed" due to the default number of "max open files" (ulimit -n) is 1024 but the loops is 10000000, if reduce the loops to 1000, the test time is too short and seems meaningless.
diff --git a/tools/perf/bench/syscall.c b/tools/perf/bench/syscall.c index c8f8bee..76571a4 100644 --- a/tools/perf/bench/syscall.c +++ b/tools/perf/bench/syscall.c @@ -57,10 +57,26 @@ static int bench_syscall_common(int argc, const char **argv, int syscall) struct timeval start, stop, diff; unsigned long long result_usec = 0; const char *name = NULL; - int i; + int i, *fd = NULL;
argc = parse_options(argc, argv, options, bench_syscall_usage, 0);
+ if (syscall == __NR_close) { + fd = (int *) malloc(sizeof(int) * loops); + if (fd == NULL) { + fprintf(stderr, "malloc failed\n"); + exit(1); + } + + for (i = 0; i < loops; i++) { + fd[i] = dup(i); + if (fd[i] < 0) { + fprintf(stderr, "dup failed\n"); + exit(1); + } + } + } + gettimeofday(&start, NULL);
for (i = 0; i < loops; i++) { @@ -69,7 +85,7 @@ static int bench_syscall_common(int argc, const char **argv, int syscall) getppid(); break; case __NR_close: - close(dup(0)); + close(fd[i]); break; case __NR_execve: test_execve(); @@ -85,6 +101,9 @@ static int bench_syscall_common(int argc, const char **argv, int syscall) gettimeofday(&stop, NULL); timersub(&stop, &start, &diff);
+ if (syscall == __NR_close) + free(fd); + switch (syscall) { case __NR_getppid: name = "getppid()"; What about the following changes? Use "open" instead of "dup" to generate fd (it nees more test time), or just leave the code as it is?
diff --git a/tools/perf/bench/syscall.c b/tools/perf/bench/syscall.c index c8f8bee..3aab5fd 100644 --- a/tools/perf/bench/syscall.c +++ b/tools/perf/bench/syscall.c @@ -57,7 +57,7 @@ static int bench_syscall_common(int argc, const char **argv, int syscall) struct timeval start, stop, diff; unsigned long long result_usec = 0; const char *name = NULL; - int i; + int i, fd;
argc = parse_options(argc, argv, options, bench_syscall_usage, 0);
@@ -69,7 +69,12 @@ static int bench_syscall_common(int argc, const char **argv, int syscall) getppid(); break; case __NR_close: - close(dup(0)); + fd = open("/etc/passwd", O_RDONLY); + if (fd < 0) { + fprintf(stderr, "open failed\n"); + exit(1); + } + close(fd); break; case __NR_execve: test_execve();
Thanks, Tiezhu
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