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Fix the isc_hp initialization and memory usage

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Previously, the isc_hp_init() could not lower the value of
isc__hp_max_threads, but because of a mistake the isc__hp_max_threads
would be set to HP_MAX_THREADS (e.g. 128 threads) thus it would be
always set to 128.  This would result in increased memory usage even
when small number of workers were in use.

Change the default value of isc__hp_max_threads to be 1.

Additionally, enforce the max_hps value in isc_hp_new() to be smaller or
equal to HP_MAX_HPS.  The only user is isc_queue which uses just 1
hazard pointer, so it's only theoretical issue.
This commit is contained in:
Ondřej Surý 2021-12-07 11:15:27 +01:00
parent 5e69cd6329
commit 15ce1737fa
1 changed files with 7 additions and 1 deletions
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8
lib/isc/hp.c
View file

@ -54,7 +54,7 @@
#include <isc/util.h>
#define HP_MAX_THREADS 128
static int isc__hp_max_threads = HP_MAX_THREADS;
static int isc__hp_max_threads = 1;
#define HP_MAX_HPS 4 /* This is named 'K' in the HP paper */
#define CLPAD (128 / sizeof(uintptr_t))
#define HP_THRESHOLD_R 0 /* This is named 'R' in the HP paper */
@ -82,9 +82,12 @@ tid(void) {
void
isc_hp_init(int max_threads) {
REQUIRE(max_threads > 0);
if (isc__hp_max_threads > max_threads) {
return;
}
isc__hp_max_threads = max_threads;
isc__hp_max_retired = max_threads * HP_MAX_HPS;
}
@ -93,6 +96,9 @@ isc_hp_t *
isc_hp_new(isc_mem_t *mctx, size_t max_hps, isc_hp_deletefunc_t *deletefunc) {
isc_hp_t *hp = isc_mem_get(mctx, sizeof(*hp));
REQUIRE(isc__hp_max_threads > 0);
REQUIRE(max_hps <= HP_MAX_HPS);
if (max_hps == 0) {
max_hps = HP_MAX_HPS;
}