From: Eric Herman <eric@xxxxxxxxxx>
Change the number of threads that we spawn from a hardcoded value of
"8" to what online_cpus() returns.
Back in v1.7.0-rc1~19^2 when threaded grep was introduced the number
of threads was hardcoded at compile time to 8, but this value was only
used if online_cpus() returned greater than 1.
However just using 8 threads regardless of the actual number of CPUs
is inefficient if we have more than 8 CPUs, and potentially wasteful
if we have fewer than 8 CPUs.
The array holding the threads is now being allocated at runtime
instead of being allocated statically. We free the array further down
the line in the wait_all() function; this is OK since the allocation
and freeing is guarded by the global "use_threads" variable, which is
based on the return value of online_cpus().
Reviewed-by: Sverre Rabbelier <srabbelier@xxxxxxxxx>
Reviewed-by: Fernando Vezzosi <buccia@xxxxxxxxx>
Signed-off-by: Eric Herman <eric@xxxxxxxxxx>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
builtin/grep.c | 17 +++++++++++------
1 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/builtin/grep.c b/builtin/grep.c
index 3d7329d..307a253 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -27,8 +27,8 @@ static char const * const grep_usage[] = {
static int use_threads = 1;
#ifndef NO_PTHREADS
-#define THREADS 8
-static pthread_t threads[THREADS];
+static int nthreads;
+static pthread_t *threads;
static void *load_sha1(const unsigned char *sha1, unsigned long *size,
const char *name);
@@ -36,7 +36,7 @@ static void *load_file(const char *filename, size_t *sz);
enum work_type {WORK_SHA1, WORK_FILE};
-/* We use one producer thread and THREADS consumer
+/* We use one producer thread and online_cpus() consumer
* threads. The producer adds struct work_items to 'todo' and the
* consumers pick work items from the same array.
*/
@@ -254,6 +254,8 @@ static void start_threads(struct grep_opt *opt)
{
int i;
+ threads = xmalloc(nthreads * sizeof(pthread_t));
+
pthread_mutex_init(&grep_mutex, NULL);
pthread_mutex_init(&read_sha1_mutex, NULL);
pthread_cond_init(&cond_add, NULL);
@@ -264,7 +266,7 @@ static void start_threads(struct grep_opt *opt)
strbuf_init(&todo[i].out, 0);
}
- for (i = 0; i < ARRAY_SIZE(threads); i++) {
+ for (i = 0; i < nthreads; i++) {
int err;
struct grep_opt *o = grep_opt_dup(opt);
o->output = strbuf_out;
@@ -295,7 +297,7 @@ static int wait_all(void)
pthread_cond_broadcast(&cond_add);
grep_unlock();
- for (i = 0; i < ARRAY_SIZE(threads); i++) {
+ for (i = 0; i < nthreads; i++) {
void *h;
pthread_join(threads[i], &h);
hit |= (int) (intptr_t) h;
@@ -307,6 +309,8 @@ static int wait_all(void)
pthread_cond_destroy(&cond_write);
pthread_cond_destroy(&cond_result);
+ free(threads);
+
return hit;
}
#else /* !NO_PTHREADS */
@@ -1001,7 +1005,8 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
opt.regflags |= REG_ICASE;
#ifndef NO_PTHREADS
- if (online_cpus() == 1 || !grep_threads_ok(&opt))
+ nthreads = online_cpus();
+ if (nthreads == 1 || !grep_threads_ok(&opt))
use_threads = 0;
if (use_threads) {
--
1.7.7
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