Re: waiting for client write

Ranier,

I did the MTU change and it did seem to bring down the clientWrite waits to
half.

The change I did was to enable ICMP to have Destination Unreachable
fragmentation needed and DF set

"When there is a difference in the MTU size in the network between two
hosts, first make sure that your network settings don't block path MTU
discovery (PMTUD). PMTUD enables the receiving host to respond to the
originating host with the following ICMP message: Destination Unreachable:
fragmentation needed and DF set (ICMP Type 3, Code 4). This message
instructs the originating host to use the lowest MTU size along the network
path to resend the request. "

https://docs.aws.amazon.com/redshift/latest/mgmt/connecting-drop-issues.html

Vijay,

Below is the pgbench result which was executed from the remote instance
pointing to RDS

postgres(at)localhost:/archive$ pgbench -h pg-cluster -p 5432 -U testuser -c
50 -j 2 -P 60 -T 600 testdb -f /archive/test.sql
starting vacuum...pgbench: error: ERROR: relation "pgbench_branches" does
not exist
pgbench: (ignoring this error and continuing anyway)
pgbench: error: ERROR: relation "pgbench_tellers" does not exist
pgbench: (ignoring this error and continuing anyway)
pgbench: error: ERROR: relation "pgbench_history" does not exist
pgbench: (ignoring this error and continuing anyway)
end.
progress: 60.0 s, 18.3 tps, lat 2631.655 ms stddev 293.592
progress: 120.0 s, 19.6 tps, lat 2533.271 ms stddev 223.722
progress: 180.0 s, 20.3 tps, lat 2446.050 ms stddev 158.397
progress: 240.1 s, 19.2 tps, lat 2575.506 ms stddev 292.418
progress: 300.0 s, 20.0 tps, lat 2482.908 ms stddev 181.770
progress: 360.0 s, 22.1 tps, lat 2245.147 ms stddev 110.855
progress: 420.0 s, 20.7 tps, lat 2397.270 ms stddev 289.324
progress: 480.0 s, 18.8 tps, lat 2625.595 ms stddev 240.250
progress: 540.0 s, 20.1 tps, lat 2467.336 ms stddev 133.121
progress: 600.0 s, 20.2 tps, lat 2455.824 ms stddev 137.976
transaction type: /archive/test.sql
scaling factor: 1
query mode: simple
number of clients: 50
number of threads: 2
duration: 600 s
number of transactions actually processed: 12007
latency average = 2480.042 ms
latency stddev = 242.243 ms
tps = 19.955602 (including connections establishing)
tps = 19.955890 (excluding connections establishing)

On Wed, Jun 9, 2021 at 5:47 PM Ayub Khan <ayub(dot)hp(at)gmail(dot)com> wrote:

> attached is the screenshot of RDS performance insights for AWS and it
> shows high waiting client writes. The api performance is slow. I read that
> this might be due to IOPS on RDS. However we have 80k IOPS on this test
> RDS.
>
> Below is the query which is being load tested
>
> SELECT
>
> a.menu_item_id,
> a.menu_item_name,
> a.menu_item_category_id,
> b.menu_item_category_desc,
> c.menu_item_variant_id,
> c.menu_item_variant_type_id,
> c.price,
> c.size_id,
> c.parent_menu_item_variant_id,
> d.menu_item_variant_type_desc,
> e.size_desc,
> f.currency_code,
> a.image,
> a.mark_id,
> m.mark_name
>
> FROM .menu_item_category AS b, .menu_item_variant AS
> c,
> .menu_item_variant_type AS d, .item_size AS e,
> .restaurant AS f,
> .menu_item AS a
>
> LEFT OUTER JOIN .mark AS m
> ON (a.mark_id = m.mark_id)
>
> WHERE a.menu_item_category_id =
> b.menu_item_category_id AND a.menu_item_id = c.menu_item_id AND
> c.menu_item_variant_type_id =
> d.menu_item_variant_type_id AND d.is_hidden = 'false' AND
> c.size_id = e.size_id AND a.restaurant_id =
> f.restaurant_id AND f.restaurant_id = 1528 AND
> (a.menu_item_category_id = NULL OR NULL IS NULL)
>
> AND c.menu_item_variant_id = (SELECT
> min(menu_item_variant_id)
> FROM
> .menu_item_variant
> WHERE
> menu_item_id = a.menu_item_id AND deleted = 'N'
> LIMIT 1) AND
> a.active = 'Y'
> AND (CONCAT_WS('', ',', a.hidden_branch_ids,
> ',') NOT LIKE CONCAT_WS('', '%,4191,%') OR
> NULL IS NULL)
> AND .is_menu_item_available(a.menu_item_id, 'Y') = 'Y'
>
> ORDER BY a.row_order, menu_item_id;
>
> --Ayub
>

--
--------------------------------------------------------------------
Sun Certified Enterprise Architect 1.5
Sun Certified Java Programmer 1.4
Microsoft Certified Systems Engineer 2000
http://in.linkedin.com/pub/ayub-khan/a/811/b81
mobile:+966-502674604
----------------------------------------------------------------------
It is proved that Hard Work and kowledge will get you close but attitude
will get you there. However, it's the Love
of God that will put you over the top!!