Increase hvn_tx_queue_size to maximize throughput

RE: Increase hvn_tx_queue_size to maximize throughput

Sigurd — Wed, 13 Jun 2018 12:19:49 GMT

[quote user="wsi-alex"]Basically the same as before but no suggestion to change RAM settings. How can this be?[/quote]

The SoftDevice does not support dynamic RAM sizes over 64 kB.

For S140 V6.0.0, the base minium requirement is at 5.54 kB, so if you configure the SoftDevice to use more RAM than 5.54 kB + 64 kB, then this is not supported, and the sd_ble_enable() function will then return NRF_ERROR_NO_MEM.

EDIT: We will look more into this limit internally, and see if we can increase it for the next SoftDevice release.

Best regards,

Sigurd

RE: Increase hvn_tx_queue_size to maximize throughput

Alexander — Tue, 12 Jun 2018 04:32:59 GMT

No when I decrease hvn_tx_queue_size or remove rows 14 - 19 it's possible to enable sd again.

RE: Increase hvn_tx_queue_size to maximize throughput

Sigurd — Fri, 08 Jun 2018 14:12:49 GMT

Interesting. If you set hvn_tx_queue_size back to 1, does the same thing happen?

RE: Increase hvn_tx_queue_size to maximize throughput

Alexander — Fri, 08 Jun 2018 13:06:33 GMT

Ok, so I ran into a similar problem again. I want to set NRF_SDH_BLE_GATT_MAX_MTU_SIZE to 247. It is currently set to 100. When I set it to 247 i get this error ouput on RTT

<warning> nrf_sdh_ble: Insufficient RAM allocated for the SoftDevice.
<warning> nrf_sdh_ble: Change the RAM start location from 0x20010DF8 to 0x2001EE58.
<warning> nrf_sdh_ble: Maximum RAM size for application is 0x211A8.
<error> nrf_sdh_ble: sd_ble_enable() returned NRF_ERROR_NO_MEM.
<error> app: ERROR 4 [NRF_ERROR_NO_MEM] at ../src/ble_core.c:435
PC at: 0x00026E85
<error> app: End of error report

I then change to those settings in my linker script and build and flash. I then get this error output

error> nrf_sdh_ble: sd_ble_enable() returned NRF_ERROR_NO_MEM.
<error> app: ERROR 4 [NRF_ERROR_NO_MEM] at ../src/ble_core.c:435
PC at: 0x00026E85
<error> app: End of error report

Basically the same as before but no suggestion to change RAM settings. How can this be?

RE: Increase hvn_tx_queue_size to maximize throughput

Sigurd — Fri, 01 Jun 2018 12:52:56 GMT

Hi,

[quote user=""]But if I increase it to above 11 i get NRF_ERROR_NO_MEM when running nrf_sdh_ble_enable(). This is fine, I check what RAM settings I should use and try, but I still get same error.[/quote]

This sounds strange. I was not able to reproduce this issue. If nrf_log is enabled, the RAM requirements for the SoftDevice will be printed over either RTT or UART(depending on nrf_log backend) e.g.

<warning> nrf_sdh_ble: Insufficient RAM allocated for the SoftDevice.
<warning> nrf_sdh_ble: Change the RAM start location from 0x20004368 to 0x20004F78.

Then you need to adjust the RAM start in the IDE/toolchain you are using.

What IDE/toolchain are you using? Where are you setting this number?

[quote user=""]Is there a max value for hvn_tx_queue_size?[/quote]

No, it should only be limited by RAM, but by setting it very big you will run out of RAM for your application.

[quote user=""]Do I need a big TX buffer to be able to send as many as 52 packets in 1 connection interval?[/quote]

Not necessarily. In the ble_app_att_mtu_throughput example we don't set the hvn_tx_queue_size in the application, but we still achieve maximum throughput. Note that both sides of the link need to support this number of packets per interval. Most smartphones only support maybe 6-9 packets per interval.

[quote user=""]Does it matter what hvn_tx_queue_size is set to if I push data really fast?[/quote]

Yes, if you exceed the event length/resources that is set aside for the link, and want to queue more data that should be send the next connection interval, you might want to increase this number. Notice the definition of the hvn_tx_queue_size, “Minimum guaranteed number of Handle Value Notifications that can be queued for transmission.”