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Implement __fsetlocking.

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The old __isthreaded hack was never very useful on Android because all user
code runs in a VM where there are lots of threads running. But __fsetlocking
lets a caller say "I'll worry about the locking for this FILE*", which is
useful for the normal case where you don't share a FILE* between threads
so you don't need any locking.

Bug: 17154740
Bug: 18593728
Change-Id: I2a8dddc29d3edff39a3d7d793387f2253608a68d
This commit is contained in:
Elliott Hughes
2015-01-20 18:09:05 -08:00
parent f374358414
commit 8c4994bbc1
5 changed files with 41 additions and 18 deletions
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16
benchmarks/stdio_benchmark.cpp
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@@ -17,6 +17,7 @@
#include "benchmark.h"
#include <stdio.h>
#include <stdio_ext.h>
#define KB 1024
#define MB 1024*KB
@@ -29,6 +30,7 @@ template <typename Fn>
static void ReadWriteTest(int iters, int chunk_size, Fn f, bool buffered) {
StopBenchmarkTiming();
FILE* fp = fopen("/dev/zero", "rw");
__fsetlocking(fp, FSETLOCKING_BYCALLER);
char* buf = new char[chunk_size];
StartBenchmarkTiming();
@@ -66,12 +68,22 @@ static void BM_stdio_fwrite_unbuffered(int iters, int chunk_size) {
}
BENCHMARK(BM_stdio_fwrite_unbuffered)->AT_COMMON_SIZES;
static void BM_stdio_fopen_fgets_fclose(int iters) {
static void FopenFgetsFclose(int iters, bool no_locking) {
char buf[1024];
for (int i = 0; i < iters; ++i) {
FILE* fp = fopen("/proc/version", "re");
if (no_locking) __fsetlocking(fp, FSETLOCKING_BYCALLER);
fgets(buf, sizeof(buf), fp);
fclose(fp);
}
}
BENCHMARK(BM_stdio_fopen_fgets_fclose);
static void BM_stdio_fopen_fgets_fclose_locking(int iters) {
FopenFgetsFclose(iters, false);
}
BENCHMARK(BM_stdio_fopen_fgets_fclose_locking);
static void BM_stdio_fopen_fgets_fclose_no_locking(int iters) {
FopenFgetsFclose(iters, true);
}
BENCHMARK(BM_stdio_fopen_fgets_fclose_no_locking);