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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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16
virtio-devices/src/pmem.rs
View file

@ -21,7 +21,6 @@ use std::fmt::{self, Display};
use std::fs::File;
use std::io;
use std::mem::size_of;
use std::ops::Deref;
use std::os::unix::io::AsRawFd;
use std::result;
use std::sync::atomic::AtomicBool;
@ -178,8 +177,7 @@ struct PmemEpollHandler {
impl PmemEpollHandler {
fn process_queue(&mut self) -> bool {
let mut used_desc_heads = [(0, 0); QUEUE_SIZE as usize];
let mut used_count = 0;
let mut used_descs = false;
while let Some(mut desc_chain) = self.queue.pop_descriptor_chain(self.mem.memory()) {
let len = match Request::parse(&mut desc_chain, self.access_platform.as_ref()) {
Ok(ref req) if (req.type_ == RequestType::Flush) => {
@ -211,15 +209,13 @@ impl PmemEpollHandler {
}
};
used_desc_heads[used_count] = (desc_chain.head_index(), len);
used_count += 1;
self.queue
.add_used(desc_chain.memory(), desc_chain.head_index(), len)
.unwrap();
used_descs = true;
}
let mem = self.mem.memory();
for &(desc_index, len) in &used_desc_heads[..used_count] {
self.queue.add_used(mem.deref(), desc_index, len).unwrap();
}
used_count > 0
used_descs
}
fn signal_used_queue(&self) -> result::Result<(), DeviceError> {