[PATCH v2 2/4] rhashtable-test: retry insert operations

Phil Sutter
2015-11-20T17:17:28Z

After adding cond_resched() calls to threadfunc(), a surprisingly high
rate of insert failures occurred probably due to table resizes getting a
better chance to run in background. To not soften up the remaining
tests, retry inserts until they either succeed or fail permanently.

Also change the non-threaded test to retry insert operations, too.

Suggested-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Phil Sutter <phil@nwl.cc>
---
lib/test_rhashtable.c | 53 ++++++++++++++++++++++++++++-----------------------
1 file changed, 29 insertions(+), 24 deletions(-)

diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c
index 63654e3..cfc3440 100644
--- a/lib/test_rhashtable.c
+++ b/lib/test_rhashtable.c
@@ -76,6 +76,20 @@ static struct rhashtable_params test_rht_params = {
static struct semaphore prestart_sem;
static struct semaphore startup_sem = __SEMAPHORE_INITIALIZER(startup_sem, 0);

+static int insert_retry(struct rhashtable *ht, struct rhash_head *obj,
+ const struct rhashtable_params params)
+{
+ int err, retries = -1;
+
+ do {
+ retries++;
+ cond_resched();
+ err = rhashtable_insert_fast(ht, obj, params);
+ } while (err == -EBUSY);
+
+ return err ? : retries;
+}
+
static int __init test_rht_lookup(struct rhashtable *ht)
{
unsigned int i;
@@ -157,7 +171,7 @@ static s64 __init test_rhashtable(struct rhashtable *ht)
{
struct test_obj *obj;
int err;
- unsigned int i, insert_fails = 0;
+ unsigned int i, insert_retries = 0;
s64 start, end;

/*
@@ -170,22 +184,16 @@ static s64 __init test_rhashtable(struct rhashtable *ht)
struct test_obj *obj = &array[i];

obj->value = i * 2;
-
- err = rhashtable_insert_fast(ht, &obj->node, test_rht_params);
- if (err == -ENOMEM || err == -EBUSY) {
- /* Mark failed inserts but continue */
- obj->value = TEST_INSERT_FAIL;
- insert_fails++;
- } else if (err) {
+ err = insert_retry(ht, &obj->node, test_rht_params);
+ if (err > 0)
+ insert_retries += err;
+ else if (err)
return err;
- }
-
- cond_resched();
}

- if (insert_fails)
- pr_info(" %u insertions failed due to memory pressure\n",
- insert_fails);
+ if (insert_retries)
+ pr_info(" %u insertions retried due to memory pressure\n",
+ insert_retries);

test_bucket_stats(ht);
rcu_read_lock();
@@ -244,7 +252,7 @@ static int thread_lookup_test(struct thread_data *tdata)

static int threadfunc(void *data)
{
- int i, step, err = 0, insert_fails = 0;
+ int i, step, err = 0, insert_retries = 0;
struct thread_data *tdata = data;

up(&prestart_sem);
@@ -253,21 +261,18 @@ static int threadfunc(void *data)

for (i = 0; i < entries; i++) {
tdata->objs[i].value = (tdata->id << 16) | i;
- cond_resched();
- err = rhashtable_insert_fast(&ht, &tdata->objs[i].node,
- test_rht_params);
- if (err == -ENOMEM || err == -EBUSY) {
- tdata->objs[i].value = TEST_INSERT_FAIL;
- insert_fails++;
+ err = insert_retry(&ht, &tdata->objs[i].node, test_rht_params);
+ if (err > 0) {
+ insert_retries += err;
} else if (err) {
pr_err(" thread[%d]: rhashtable_insert_fast failed\n",
tdata->id);
goto out;
}
}
- if (insert_fails)
- pr_info(" thread[%d]: %d insert failures\n",
- tdata->id, insert_fails);
+ if (insert_retries)
+ pr_info(" thread[%d]: %u insertions retried due to memory pressure\n",
+ tdata->id, insert_retries);

err = thread_lookup_test(tdata);
if (err) {
--
2.1.2