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virtio-devices: Optimize add_used() usage

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Now that we rely on pop_descriptor_chain() rather than iter() to iterate
over a queue, there's no more borrow on the queue itself, meaning we can
invoke add_used() directly for the iteration loop. This simplifies the
processing of the queues for each virtio device, and bring some possible
performance improvement given we don't have to iterate twice over the
list of descriptors to invoke add_used().

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
This commit is contained in:
Sebastien Boeuf
2022-07-25 14:26:17 +02:00
committed by Rob Bradford
parent 87f57f7c1e
commit a4859ffe85
11 changed files with 111 additions and 179 deletions
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31
virtio-devices/src/block.rs
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@@ -105,8 +105,7 @@ impl BlockEpollHandler {
fn process_queue_submit(&mut self) -> Result<bool> {
let queue = &mut self.queue;
let mut used_desc_heads = Vec::new();
let mut used_count = 0;
let mut used_descs = false;
while let Some(mut desc_chain) = queue.pop_descriptor_chain(self.mem.memory()) {
let mut request = Request::parse(&mut desc_chain, self.access_platform.as_ref())
@@ -166,26 +165,20 @@ impl BlockEpollHandler {
// If no asynchronous operation has been submitted, we can
// simply return the used descriptor.
used_desc_heads.push((desc_chain.head_index(), 0));
used_count += 1;
queue
.add_used(desc_chain.memory(), desc_chain.head_index(), 0)
.map_err(Error::QueueAddUsed)?;
used_descs = true;
}
}
let mem = self.mem.memory();
for &(desc_index, len) in used_desc_heads.iter() {
queue
.add_used(mem.deref(), desc_index, len)
.map_err(Error::QueueAddUsed)?;
}
Ok(used_count > 0)
Ok(used_descs)
}
fn process_queue_complete(&mut self) -> Result<bool> {
let queue = &mut self.queue;
let mut used_desc_heads = Vec::new();
let mut used_count = 0;
let mut used_descs = false;
let mem = self.mem.memory();
let mut read_bytes = Wrapping(0);
let mut write_bytes = Wrapping(0);
@@ -234,14 +227,10 @@ impl BlockEpollHandler {
// checked that the status_addr was valid.
mem.write_obj(status, request.status_addr).unwrap();
used_desc_heads.push((desc_index as u16, len));
used_count += 1;
}
for &(desc_index, len) in used_desc_heads.iter() {
queue
.add_used(mem.deref(), desc_index, len)
.add_used(mem.deref(), desc_index as u16, len)
.map_err(Error::QueueAddUsed)?;
used_descs = true;
}
self.counters
@@ -258,7 +247,7 @@ impl BlockEpollHandler {
.read_ops
.fetch_add(read_ops.0, Ordering::AcqRel);
Ok(used_count > 0)
Ok(used_descs)
}
fn signal_used_queue(&self) -> result::Result<(), DeviceError> {