On 8/24/21 9:00 PM, Ilya Maximets wrote:
> Same json from a json cache is typically sent to all the clients,
> e.g., in case of OVN deployment with ovn-monitor-all=true.
>
> There could be hundreds or thousands connected clients and ovsdb
> will serialize the same json object for each of them before sending.
>
> Serializing it once before storing into json cache to speed up
> processing.
>
> This change allows to save a lot of CPU cycles and a bit of memory
> since we need to store in memory only a string and not the full json
> object.
>
> Testing with ovn-heater on 120 nodes using density-heavy scenario
> shows reduction of the total CPU time used by Southbound DB processes
> from 256 minutes to 147. Duration of unreasonably long poll intervals
> also reduced dramatically from 7 to 2 seconds:
>
> Count Min Max Median Mean 95 percentile
> -------------------------------------------------------------
> Before 1934 1012 7480 4302.5 4875.3 7034.3
> After 1909 1004 2730 1453.0 1532.5 2053.6
>
> Signed-off-by: Ilya Maximets <i.maxim...@ovn.org>
> ---
> ovsdb/monitor.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/ovsdb/monitor.c b/ovsdb/monitor.c
> index 532dedcb6..ab814cf20 100644
> --- a/ovsdb/monitor.c
> +++ b/ovsdb/monitor.c
> @@ -1231,6 +1231,15 @@ ovsdb_monitor_get_update(
> condition,
>
> ovsdb_monitor_compose_row_update2);
> if (!condition || !condition->conditional) {
> + if (json) {
> + struct json *json_serialized;
> +
> + /* Pre-serializing the object to avoid doing this
> + * for every client. */
> + json_serialized =
> json_serialized_object_create(json);
> + json_destroy(json);
> + json = json_serialized;
> + }
I think this could be part of ovsdb_monitor_json_cache_insert()
directly. It would save a level of indentation here and it seems to me
like it's just an implementation decision about how to store the cached
json.
Either way:
Acked-by: Dumitru Ceara <dce...@redhat.com>
> ovsdb_monitor_json_cache_insert(dbmon, version, mcs,
> json);
> }
>
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