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Reduce stack-allocations (esp-rs#243)
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* Reduce stack-allocations

* Avoid explicit panic on exhausted backing memory

* Remove unnecessary `transmute`
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@bjoernQ
bjoernQ committed May 23, 2024
1 parent 182c82e commit 0d79d7a
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Showing 2 changed files with 87 additions and 28 deletions.
3 changes: 3 additions & 0 deletions esp-wifi/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -277,6 +277,9 @@ pub fn initialize(
rom_ets_update_cpu_frequency(240); // we know it's 240MHz because of the check above
}

#[cfg(feature = "wifi")]
crate::wifi::DataFrame::internal_init();

log::info!("esp-wifi configuration {:?}", crate::CONFIG);

crate::common_adapter::chip_specific::enable_wifi_power_domain();
Expand Down
112 changes: 84 additions & 28 deletions esp-wifi/src/wifi/mod.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
#[doc(hidden)]
pub mod os_adapter;

use core::{cell::RefCell, marker::PhantomData, mem::MaybeUninit};
use core::{cell::RefCell, mem::MaybeUninit};

use crate::common_adapter::*;
use crate::EspWifiInitialization;
Expand Down Expand Up @@ -31,6 +31,7 @@ use esp_wifi_sys::include::wifi_interface_t_WIFI_IF_AP;
use esp_wifi_sys::include::wifi_mode_t_WIFI_MODE_AP;
use esp_wifi_sys::include::wifi_mode_t_WIFI_MODE_APSTA;
use esp_wifi_sys::include::wifi_mode_t_WIFI_MODE_NULL;
use heapless::Vec;
use num_derive::FromPrimitive;
use num_traits::FromPrimitive;

Expand Down Expand Up @@ -97,31 +98,72 @@ impl WifiMode {
}
}

const DATA_FRAMES_MAX_COUNT: usize = RX_QUEUE_SIZE + RX_QUEUE_SIZE;
const DATA_FRAME_SIZE: usize = MTU + ETHERNET_FRAME_HEADER_SIZE;

static mut DATA_FRAME_BACKING_MEMORY: MaybeUninit<[u8; DATA_FRAMES_MAX_COUNT * DATA_FRAME_SIZE]> =
MaybeUninit::uninit();

static DATA_FRAME_BACKING_MEMORY_FREE_SLOTS: Mutex<RefCell<Vec<usize, DATA_FRAMES_MAX_COUNT>>> =
Mutex::new(RefCell::new(Vec::new()));

#[derive(Debug, Clone, Copy)]
pub(crate) struct DataFrame<'a> {
pub(crate) struct DataFrame {
len: usize,
data: [u8; MTU + ETHERNET_FRAME_HEADER_SIZE],
_phantom: PhantomData<&'a ()>,
index: usize,
}

impl<'a> DataFrame<'a> {
pub(crate) fn new() -> DataFrame<'a> {
DataFrame {
len: 0,
data: [0u8; MTU + ETHERNET_FRAME_HEADER_SIZE],
_phantom: Default::default(),
impl DataFrame {
pub(crate) fn internal_init() {
critical_section::with(|cs| {
let mut free_slots = DATA_FRAME_BACKING_MEMORY_FREE_SLOTS.borrow_ref_mut(cs);
for i in 0..DATA_FRAMES_MAX_COUNT {
free_slots.push(i).unwrap();
}
});
}

pub(crate) fn new() -> Option<DataFrame> {
let index = critical_section::with(|cs| {
DATA_FRAME_BACKING_MEMORY_FREE_SLOTS
.borrow_ref_mut(cs)
.pop()
});

match index {
Some(index) => Some(DataFrame { len: 0, index }),
None => None,
}
}

pub(crate) fn from_bytes(bytes: &[u8]) -> DataFrame {
let mut data = DataFrame::new();
pub(crate) fn free(self) {
critical_section::with(|cs| {
let mut free_slots = DATA_FRAME_BACKING_MEMORY_FREE_SLOTS.borrow_ref_mut(cs);
free_slots.push(self.index).unwrap();
});
}

pub(crate) fn data_mut(&mut self) -> &mut [u8] {
let data = unsafe { DATA_FRAME_BACKING_MEMORY.assume_init_mut() };
&mut data[(self.index * DATA_FRAME_SIZE)..][..DATA_FRAME_SIZE]
}

pub(crate) fn from_bytes(bytes: &[u8]) -> Option<DataFrame> {
let mut data = DataFrame::new()?;
data.len = bytes.len();
data.data[..bytes.len()].copy_from_slice(bytes);
data
let mem = unsafe { DATA_FRAME_BACKING_MEMORY.assume_init_mut() };
let len = usize::min(bytes.len(), DATA_FRAME_SIZE);
if len != bytes.len() {
log::warn!("Trying to store more data than available into DataFrame. Check MTU");
}

mem[(data.index * DATA_FRAME_SIZE)..][..len].copy_from_slice(bytes);
Some(data)
}

pub(crate) fn slice(&'a self) -> &'a [u8] {
&self.data[..self.len]
pub(crate) fn slice(&self) -> &[u8] {
let data = unsafe { DATA_FRAME_BACKING_MEMORY.assume_init_ref() };
&data[(self.index * DATA_FRAME_SIZE)..][..self.len]
}
}

Expand Down Expand Up @@ -609,7 +651,11 @@ unsafe extern "C" fn recv_cb(
eb: *mut crate::binary::c_types::c_void,
) -> esp_err_t {
let src = core::slice::from_raw_parts_mut(buffer as *mut u8, len as usize);
let packet = DataFrame::from_bytes(src);
let packet = if let Some(packet) = DataFrame::from_bytes(src) {
packet
} else {
return esp_wifi_sys::include::ESP_ERR_NO_MEM as esp_err_t;
};

let res = critical_section::with(|cs| {
let mut queue = DATA_QUEUE_RX.borrow_ref_mut(cs);
Expand All @@ -621,10 +667,12 @@ unsafe extern "C" fn recv_cb(

0
} else {
packet.free();
log::error!("RX QUEUE FULL");
1
}
});

esp_wifi_internal_free_rx_buffer(eb);

res
Expand Down Expand Up @@ -978,9 +1026,12 @@ impl RxToken for WifiRxToken {
let mut data = queue
.dequeue()
.expect("unreachable: transmit()/receive() ensures there is a packet to process");
let buffer = unsafe { core::slice::from_raw_parts(&data.data as *const u8, data.len) };
let len = data.len;
let buffer = &mut data.data_mut()[..len];
dump_packet_info(&buffer);
f(&mut data.data[..])
let res = f(buffer);
data.free();
res
})
}
}
Expand All @@ -996,9 +1047,9 @@ impl TxToken for WifiTxToken {
let res = critical_section::with(|cs| {
let mut queue = DATA_QUEUE_TX.borrow_ref_mut(cs);

let mut packet = DataFrame::new();
let mut packet = DataFrame::new().expect("unreachable: transmit()/receive() ensures there is a buffer free (which means we also have free buffer space)");
packet.len = len;
let res = f(&mut packet.data[..len]);
let res = f(&mut packet.data_mut()[..len]);
queue
.enqueue(packet)
.expect("unreachable: transmit()/receive() ensures there is a buffer free");
Expand All @@ -1024,7 +1075,7 @@ pub fn send_data_if_needed() {
wifi_mode_t_WIFI_MODE_AP | wifi_mode_t_WIFI_MODE_APSTA
);

while let Some(packet) = queue.dequeue() {
while let Some(mut packet) = queue.dequeue() {
log::trace!("sending... {} bytes", packet.len);
dump_packet_info(packet.slice());

Expand All @@ -1037,7 +1088,7 @@ pub fn send_data_if_needed() {
unsafe {
let _res = esp_wifi_internal_tx(
interface,
&packet.data as *const _ as *mut crate::binary::c_types::c_void,
packet.data_mut() as *const _ as *mut crate::binary::c_types::c_void,
packet.len as u16,
);
if _res != 0 {
Expand All @@ -1047,6 +1098,8 @@ pub fn send_data_if_needed() {
}
#[cfg(feature = "embassy-net")]
embassy::TRANSMIT_WAKER.wake();

packet.free();
}
});
}
Expand Down Expand Up @@ -1287,10 +1340,12 @@ pub(crate) mod embassy {
let mut data = queue.dequeue().expect(
"unreachable: transmit()/receive() ensures there is a packet to process",
);
let buffer =
unsafe { core::slice::from_raw_parts(&data.data as *const u8, data.len) };
let len = data.len;
let buffer = &mut data.data_mut()[..len];
dump_packet_info(&buffer);
f(&mut data.data[..])
let res = f(buffer);
data.free();
res
})
}
}
Expand All @@ -1303,9 +1358,10 @@ pub(crate) mod embassy {
let res = critical_section::with(|cs| {
let mut queue = DATA_QUEUE_TX.borrow_ref_mut(cs);

let mut packet = DataFrame::new();
let mut packet = DataFrame::new().expect("unreachable: transmit()/receive() ensures there is a buffer free and space available");

packet.len = len;
let res = f(&mut packet.data[..len]);
let res = f(&mut packet.data_mut()[..len]);
queue
.enqueue(packet)
.expect("unreachable: transmit()/receive() ensures there is a buffer free");
Expand Down

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