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vhost_user_blk: Make DiskFile sharable across threads

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The DiskFile will need to be shared across multiple threads when running
multiple queues across these threads. That's why it needs to be put
inside an Arc. The reason for the Mutex is because execute() expects a
mutable object implementing Read + Write + Seek. Unfortunately, this
create a contention point as the object needs to be locked from each
thread, reducing the performance gain we will get with multiple threads.

The need for an immutable object would solve this problem, and it will
be addressed later through follow up patches.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
This commit is contained in:
Sebastien Boeuf 2020-04-16 17:13:08 +02:00
parent 808586ece7
commit e78e34b36a
1 changed files with 9 additions and 6 deletions
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15
vhost_user_block/src/lib.rs
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@ -23,6 +23,7 @@ use std::io::Read;
use std::io::{Seek, SeekFrom, Write};
use std::mem;
use std::num::Wrapping;
use std::ops::DerefMut;
use std::os::unix::fs::OpenOptionsExt;
use std::path::PathBuf;
use std::process;
@ -98,7 +99,7 @@ impl convert::From<Error> for io::Error {
pub struct VhostUserBlkThread {
mem: Option<GuestMemoryMmap>,
disk_image: Box<dyn DiskFile>,
disk_image: Arc<Mutex<dyn DiskFile>>,
disk_image_id: Vec<u8>,
disk_nsectors: u64,
config: virtio_blk_config,
@ -127,12 +128,14 @@ impl VhostUserBlkThread {
let image_id = build_disk_image_id(&PathBuf::from(&image_path));
let image_type = qcow::detect_image_type(&mut raw_img).unwrap();
let mut image = match image_type {
ImageType::Raw => Box::new(raw_img) as Box<dyn DiskFile>,
ImageType::Qcow2 => Box::new(QcowFile::from(raw_img).unwrap()) as Box<dyn DiskFile>,
let image = match image_type {
ImageType::Raw => Arc::new(Mutex::new(raw_img)) as Arc<Mutex<dyn DiskFile>>,
ImageType::Qcow2 => {
Arc::new(Mutex::new(QcowFile::from(raw_img).unwrap())) as Arc<Mutex<dyn DiskFile>>
}
};
let nsectors = (image.seek(SeekFrom::End(0)).unwrap() as u64) / SECTOR_SIZE;
let nsectors = (image.lock().unwrap().seek(SeekFrom::End(0)).unwrap() as u64) / SECTOR_SIZE;
let mut config = virtio_blk_config::default();
config.capacity = nsectors;
@ -171,7 +174,7 @@ impl VhostUserBlkThread {
Ok(request) => {
debug!("element is a valid request");
let status = match request.execute(
&mut self.disk_image,
&mut self.disk_image.lock().unwrap().deref_mut(),
self.disk_nsectors,
mem,
&self.disk_image_id,