On 25/08/2021 08:35, [email protected] wrote:
From: Anton Ivanov <[email protected]>
When running with dp_groups and parallelization enabled we have
a possible worse case scenario where northd connects for the
first time to a pre-populated database.
If we do not size the hash to a sufficiently big size to
accommodate for this, we end up with severe lock contention
and very slow lookups.
If both dp_groups and parallelization are enabled we have
no choice, but to allocate for a worst case scenario on the
first run and adjust later.
Signed-off-by: Anton Ivanov <[email protected]>
---
northd/ovn-northd.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
index 14659c407..3a5ab1d9f 100644
--- a/northd/ovn-northd.c
+++ b/northd/ovn-northd.c
@@ -13034,7 +13034,7 @@ ovn_sb_set_lflow_logical_dp_group(
sbrec_logical_flow_set_logical_dp_group(sbflow, dpg->dp_group);
}
-static ssize_t max_seen_lflow_size = 128;
+static ssize_t max_seen_lflow_size = 0;
/* Updates the Logical_Flow and Multicast_Group tables in the OVN_SB database,
* constructing their contents based on the OVN_NB database. */
@@ -13048,6 +13048,25 @@ build_lflows(struct northd_context *ctx, struct hmap
*datapaths,
{
struct hmap lflows;
+ if (!max_seen_lflow_size) {
+ if (use_logical_dp_groups && use_parallel_build) {
+ /* We are running for the first time. The user has
+ * requested both dp_groups and parallelisation. We
+ * may encounter a very large amount of flows on first
+ * run and we have no way to guess the flow hash size.
+ * We allocate for worst a case scenario on the first
+ * run. This will be resized to a sane size later. */
+ max_seen_lflow_size = INT_MAX;
This ends up being too big for most systems. First run has to be in single
threaded mode.
+ } else {
+ /* If the build is not parallel, this will be resized
+ * to a correct size. If it is parallel, but without
+ * dp_groups, the sizing is irrelevant as the hash is
+ * not used for lookups during build. We resize it to
+ * a correct size after that. */
+ max_seen_lflow_size = 128;
+ }
+ }
+
fast_hmap_size_for(&lflows, max_seen_lflow_size);
if (use_parallel_build) {
update_hashrow_locks(&lflows, &lflow_locks);
--
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/
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