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virtio: batch page removal in balloon

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In a long-running system, there is no reason to expect that a
significant number of freed pages are consecutive. However, batching is
relatively simple and can result in significant gains in a newly booted
system, so it's worth attempting.

BUG=None
TEST=arc.Boot.vm

Change-Id: Ia7dff4ab095d640a2a23ac4976bc277b09d9ea79
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2666412
Commit-Queue: David Stevens <stevensd@chromium.org>
Tested-by: David Stevens <stevensd@chromium.org>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
This commit is contained in:
David Stevens 2021-02-02 17:05:04 +09:00 committed by Commit Bot
parent 9463e3720a
commit 229cbead14
1 changed files with 37 additions and 12 deletions
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49
devices/src/virtio/balloon.rs
View file

@ -46,6 +46,7 @@ const QUEUE_SIZE: u16 = 128;
const QUEUE_SIZES: &[u16] = &[QUEUE_SIZE, QUEUE_SIZE, QUEUE_SIZE];
const VIRTIO_BALLOON_PFN_SHIFT: u32 = 12;
const VIRTIO_BALLOON_PF_SIZE: u64 = 1 << VIRTIO_BALLOON_PFN_SHIFT;
// The feature bitmap for virtio balloon
const VIRTIO_BALLOON_F_MUST_TELL_HOST: u32 = 0; // Tell before reclaiming pages
@ -118,8 +119,14 @@ fn handle_address_chain<F>(
desc_handler: &mut F,
) -> descriptor_utils::Result<()>
where
F: FnMut(GuestAddress),
F: FnMut(GuestAddress, u64),
{
// In a long-running system, there is no reason to expect that
// a significant number of freed pages are consecutive. However,
// batching is relatively simple and can result in significant
// gains in a newly booted system, so it's worth attempting.
let mut range_start = 0;
let mut range_size = 0;
let mut reader = Reader::new(mem.clone(), avail_desc)?;
for res in reader.iter::<Le32>() {
let pfn = match res {
@ -129,9 +136,24 @@ where
break;
}
};
let guest_address = GuestAddress((u64::from(pfn.to_native())) << VIRTIO_BALLOON_PFN_SHIFT);
desc_handler(guest_address);
let guest_address = (u64::from(pfn.to_native())) << VIRTIO_BALLOON_PFN_SHIFT;
if range_start + range_size == guest_address {
range_size += VIRTIO_BALLOON_PF_SIZE;
} else if range_start == guest_address + VIRTIO_BALLOON_PF_SIZE {
range_start = guest_address;
range_size += VIRTIO_BALLOON_PF_SIZE;
} else {
// Discontinuity, so flush the previous range. Note range_size
// will be 0 on the first iteration, so skip that.
if range_size != 0 {
desc_handler(GuestAddress(range_start), range_size);
}
range_start = guest_address;
range_size = VIRTIO_BALLOON_PF_SIZE;
}
}
if range_size != 0 {
desc_handler(GuestAddress(range_start), range_size);
}
Ok(())
}
@ -144,7 +166,7 @@ async fn handle_queue<F>(
interrupt: Rc<RefCell<Interrupt>>,
mut desc_handler: F,
) where
F: FnMut(GuestAddress),
F: FnMut(GuestAddress, u64),
{
loop {
let avail_desc = match queue.next_async(mem, &mut queue_event).await {
@ -303,8 +325,8 @@ fn run_worker(
queues.remove(0),
inflate_event,
interrupt.clone(),
|guest_address| {
if let Err(e) = mem.remove_range(guest_address, 1 << VIRTIO_BALLOON_PFN_SHIFT) {
|guest_address, len| {
if let Err(e) = mem.remove_range(guest_address, len) {
warn!("Marking pages unused failed: {}, addr={}", e, guest_address);
}
},
@ -319,7 +341,7 @@ fn run_worker(
queues.remove(0),
deflate_event,
interrupt.clone(),
std::mem::drop, // Ignore these.
|_, _| {}, // Ignore these.
);
pin_mut!(deflate);
@ -542,14 +564,17 @@ mod tests {
.expect("create_descriptor_chain failed");
let mut addrs = Vec::new();
let res = handle_address_chain(chain, &memory, &mut |guest_address| {
addrs.push(guest_address);
let res = handle_address_chain(chain, &memory, &mut |guest_address, len| {
addrs.push((guest_address, len));
});
assert!(res.is_ok());
assert_eq!(addrs.len(), 2);
assert_eq!(addrs[0], GuestAddress(0x10u64 << VIRTIO_BALLOON_PFN_SHIFT));
assert_eq!(
addrs[1],
addrs[0].0,
GuestAddress(0x10u64 << VIRTIO_BALLOON_PFN_SHIFT)
);
assert_eq!(
addrs[1].0,
GuestAddress(0xaa55aa55u64 << VIRTIO_BALLOON_PFN_SHIFT)
);
}