BLE subsystem host RAM increase when migrating from NCS 2.5.0 to 2.7.0

RE: BLE subsystem host RAM increase when migrating from NCS 2.5.0 to 2.7.0

Susheel Nuguru — Tue, 27 Aug 2024 08:06:40 GMT

These two are application configurable buffers with defaults set in zephyr\subsys\bluetooth\common\Kconfig

I think the difference comes from here

And we can see that the BT_RECV_BLOCKING is removed in new version so it looks like the default changed from 3 to 20

RE: BLE subsystem host RAM increase when migrating from NCS 2.5.0 to 2.7.0

PuffinEgg — Fri, 23 Aug 2024 19:53:11 GMT

You are right it looks like the option is deprecated in Zephyr 3.4.99. I wonder if there is a way to see which config selects the count value in previous Zephyr releases.

RE: BLE subsystem host RAM increase when migrating from NCS 2.5.0 to 2.7.0

Susheel Nuguru — Fri, 23 Aug 2024 04:49:52 GMT

I do not see this config (COFIG_BT_RECV_IS_RX_THREAD ) at all in both the SDK versions. Can you please link me to the documentation for this?

RE: BLE subsystem host RAM increase when migrating from NCS 2.5.0 to 2.7.0

PuffinEgg — Tue, 20 Aug 2024 17:13:45 GMT

Actually, I see the default was 3 when COFIG_BT_RECV_IS_RX_THREAD is selected. However, the default seems to be set to 10 and 6 for the latest version, and COFIG_BT_RECV_IS_RX_THREAD no longer seem to exist?

RE: BLE subsystem host RAM increase when migrating from NCS 2.5.0 to 2.7.0

PuffinEgg — Tue, 20 Aug 2024 16:34:30 GMT

For some reason BT_BUF_EVT_RX_COUNT was set to 10, and BT_BUF_ACL_RX_COUNT was set to 6. Both of them were set to 3 in the previous SDK version(2.5.0). I manually changed them back to 3 and I was able to get back to the memory usage before. However, I am not sure which module is setting these numbers and I am a bit concerned to if I should manually set them to a lower value.

RE: BLE subsystem host RAM increase when migrating from NCS 2.5.0 to 2.7.0

Susheel Nuguru — Tue, 20 Aug 2024 06:49:08 GMT

I have checked the peripheral_uart sample and net_buf_data_hci_rx_pool changed from 730->740 bytes in this sample.

Looking into the host\buf.c it looks like this buffer is depending on

CONFIG_BT_BUF_EVT_RX_COUNT
CONFIG_BT_BUF_EVT_RX_SIZE
CONFIG_BT_BUF_ACL_RX_COUNT
CONFIG_BT_BUF_ACL_RX_SIZE

Check if these things changed in your new port. I do not see anything else affecting this.