[WIP] Nydusd: introduce runtime streaming prefetching

rafs/src/fs.rs

@@ -175,8 +175,10 @@ impl Rafs {
         }
         if self.fs_prefetch {
             // Device should be ready before any prefetch.
-            self.device.start_prefetch();
-            self.prefetch(r, prefetch_files);
+            // self.device.start_prefetch();
+            // self.prefetch(r, prefetch_files);
+            self.device.init_stream_prefetch();
+            self.start_stream_prefetch(r, prefetch_files);
         }
         self.initialized = true;
 
@@ -327,6 +329,7 @@ impl Rafs {
 }
 
 impl Rafs {
+    #[allow(unused)]
     fn prefetch(&self, reader: RafsIoReader, prefetch_files: Option<Vec<PathBuf>>) {
         let sb = self.sb.clone();
         let device = self.device.clone();
@@ -338,6 +341,18 @@ impl Rafs {
         });
     }
 
+    #[allow(unused)]
+    fn start_stream_prefetch(&self, reader: RafsIoReader, prefetch_files: Option<Vec<PathBuf>>) {
+        let sb = self.sb.clone();
+        let device = self.device.clone();
+        let prefetch_all = self.prefetch_all;
+        let root_ino = self.root_ino();
+
+        let _ = std::thread::spawn(move || {
+            Self::do_stream_prefetch(root_ino, reader, prefetch_files, prefetch_all, sb, device);
+        });
+    }
+
     /// for blobfs
     pub fn fetch_range_synchronous(&self, prefetches: &[BlobPrefetchRequest]) -> Result<()> {
         self.device.fetch_range_synchronous(prefetches)
@@ -347,6 +362,7 @@ impl Rafs {
         self.sb.superblock.root_ino()
     }
 
+    #[allow(unused)]
     fn do_prefetch(
         root_ino: u64,
         mut reader: RafsIoReader,
@@ -472,6 +488,45 @@ impl Rafs {
         }
     }
 
+    fn do_stream_prefetch(
+        root_ino: u64,
+        mut reader: RafsIoReader,
+        prefetch_files: Option<Vec<PathBuf>>,
+        _prefetch_all: bool,
+        sb: Arc<RafsSuper>,
+        device: BlobDevice,
+    ) {
+        // Bootstrap has non-empty prefetch table indicating a full prefetch
+        let inlay_prefetch_all = sb
+            .is_inlay_prefetch_all(&mut reader)
+            .map_err(|e| error!("Detect prefetch table error {}", e))
+            .unwrap_or_default();
+
+        // Nydusd has a CLI option indicating a full prefetch
+        let startup_prefetch_all = prefetch_files
+            .as_ref()
+            .map(|f| f.len() == 1 && f[0].as_os_str() == "/")
+            .unwrap_or(false);
+
+        // User specified prefetch files have high priority to be prefetched.
+        // Moreover, user specified prefetch files list will override those on-disk prefetch table.
+        if !startup_prefetch_all && !inlay_prefetch_all {
+            // Then do file based prefetch based on:
+            // - prefetch listed passed in by user
+            // - or file prefetch list in metadata
+            // TODO: change this to iterator
+            let inodes = prefetch_files.map(|files| Self::convert_file_list(&files, &sb));
+            let res = sb.stream_prefetch_files(&device, &mut reader, root_ino, inodes);
+            match res {
+                Ok(true) => {
+                    info!("Root inode was found, but it should not prefetch all files!")
+                }
+                Ok(false) => {}
+                Err(e) => error!("No file to be prefetched {:?}", e),
+            }
+        }
+    }
+
     fn convert_file_list(files: &[PathBuf], sb: &Arc<RafsSuper>) -> Vec<Inode> {
         let mut inodes = Vec::<Inode>::with_capacity(files.len());
 

rafs/src/metadata/direct_v6.rs

@@ -847,6 +847,7 @@ impl RafsInode for OndiskInodeWrapper {
                         curr_chunk_index == tail_chunk_index,
                     )
                     .ok_or_else(|| einval!("failed to get chunk information"))?;
+                //TODO:这里应该考虑某个中间的chunk的blob_index不同的情况
                 if desc.blob.blob_index() != descs.blob_index() {
                     vec.push(descs);
                     descs = BlobIoVec::new(desc.blob.clone());

rafs/src/metadata/md_v6.rs

@@ -151,6 +151,74 @@ impl RafsSuper {
 
         Ok(found_root_inode)
     }
+
+    pub(crate) fn stream_prefetch_data_v6(
+        &self,
+        device: &BlobDevice,
+        rafs_reader: &mut RafsIoReader,
+        root_ino: Inode,
+    ) -> RafsResult<bool> {
+        let hint_entries = self.meta.prefetch_table_entries as usize;
+        if hint_entries == 0 {
+            return Ok(false);
+        }
+
+        // Try to prefetch according to the list of files specified by the
+        // builder's `--prefetch-policy fs` option.
+        let mut prefetch_table = RafsV6PrefetchTable::new();
+        prefetch_table
+            .load_prefetch_table_from(rafs_reader, self.meta.prefetch_table_offset, hint_entries)
+            .map_err(|e| {
+                error!("Failed in loading hint prefetch table at offset {}", e);
+                RafsError::Prefetch(format!(
+                    "Failed in loading hint prefetch table at offset {}. {:?}",
+                    self.meta.prefetch_table_offset, e
+                ))
+            })?;
+        // debug!("prefetch table contents {:?}", prefetch_table);
+
+        let mut hardlinks: HashSet<u64> = HashSet::new();
+        let mut fetched_ranges: HashMap<u32, HashSet<u32>> = HashMap::new();
+        let blob_ccis = device.get_all_blob_cci();
+
+        let mut found_root_inode = false;
+        for ino in prefetch_table.inodes {
+            // Inode number 0 is invalid, it was added because prefetch table has to be aligned.
+            if ino == 0 {
+                break;
+            }
+            if ino as Inode == root_ino {
+                found_root_inode = true;
+            }
+            // debug!("CMDebug: hint prefetch inode {}", ino);
+
+            let ranges = self
+                .get_inode_ranges(
+                    ino as u64,
+                    &mut hardlinks,
+                    &mut fetched_ranges,
+                    device,
+                    &blob_ccis,
+                )
+                .map_err(|e| {
+                    RafsError::Prefetch(format!("Failed in get inode chunk ranges. {:?}", e))
+                })?;
+
+            // debug!("CMDebug: prefetch inode: {}, ranges: {:?}", ino, ranges);
+
+            for r in ranges {
+                device.add_stream_prefetch_range(r).map_err(|e| {
+                    RafsError::Prefetch(format!("Failed to add inode prefetch range. {:?}", e))
+                })?;
+            }
+        }
+
+        device.flush_stream_prefetch().map_err(|e| {
+            RafsError::Prefetch(format!("Failed to flush inode prefetch range. {:?}", e))
+        })?;
+
+        Ok(found_root_inode)
+    }
 }
 
 #[cfg(test)]