local cas: solving the mismatch between nydus chunk amplification and…

… dynamic dedup.

The mismatch between dynamic dedup and nydus' chunk amplification can
result in a larger cache size after dedup than without dedup. Because
chunk amplification can cause reused chunks to be pulled multiple
times, resulting in a larger cache size after dedup is enabled than when
dedup is not enabled.

To address this issue, a dedup_bitmap was introduced. When initializing
rafs, dedup_bitmap is generated based on the chunk information in blob.
The determination of whether a chunk in a blob is ready requires both
the chunk map and deduplication bitmap to make a joint decision.

Signed-off-by: xwb1136021767 <[email protected]>

builder/Cargo.toml

@@ -22,7 +22,7 @@ erased-serde = "0.3"
 sha2 = "0.10.2"
 tar = "0.4.40"
 vmm-sys-util = "0.11.0"
-xattr = "0.2.3"
+xattr = "1.0.1"
 toml = "0.5"
 bitvec = { version="1", default-features = false, features = ["alloc",
   "atomic",

rafs/Cargo.toml

@@ -16,10 +16,14 @@ lazy_static = "1.4.0"
 libc = "0.2"
 log = "0.4"
 nix = "0.24"
-serde = { version = "1.0.110", features = ["serde_derive", "rc"] }
+serde = { version = "1.0.137", features = ["derive", "rc"] }
 serde_json = "1.0.53"
 vm-memory = "0.10"
 fuse-backend-rs = "^0.10.3"
+bitvec = { version="1", default-features = false, features = ["alloc",
+  "atomic",
+  "serde",
+  "std",]}
 
 nydus-api = { version = "0.3", path = "../api" }
 nydus-storage = { version = "0.6", path = "../storage", features = ["backend-localfs"] }

rafs/src/fs.rs

@@ -18,12 +18,14 @@ use std::any::Any;
 use std::cmp;
 use std::ffi::{CStr, OsStr, OsString};
 use std::io::Result;
+use std::mem::size_of;
 use std::ops::Deref;
 use std::os::unix::ffi::OsStrExt;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 use std::time::{Duration, SystemTime};
 
+use bitvec::prelude::*;
 use fuse_backend_rs::abi::fuse_abi::Attr;
 use fuse_backend_rs::abi::fuse_abi::{stat64, statvfs64};
 use fuse_backend_rs::api::filesystem::*;
@@ -38,6 +40,7 @@ use nydus_utils::{
     metrics::{self, FopRecorder, StatsFop::*},
 };
 
+use crate::metadata::layout::v5::RafsV5ChunkInfo;
 use crate::metadata::{
     Inode, RafsInode, RafsInodeWalkAction, RafsSuper, RafsSuperMeta, DOT, DOTDOT,
 };
@@ -81,12 +84,39 @@ impl Rafs {
     pub fn new(cfg: &Arc<ConfigV2>, id: &str, path: &Path) -> RafsResult<(Self, RafsIoReader)> {
         // Assume all meta/data blobs are accessible, otherwise it will always cause IO errors.
         cfg.internal.set_blob_accessible(true);
-
         let cache_cfg = cfg.get_cache_config().map_err(RafsError::LoadConfig)?;
         let rafs_cfg = cfg.get_rafs_config().map_err(RafsError::LoadConfig)?;
         let (sb, reader) = RafsSuper::load_from_file(path, cfg.clone(), false)
             .map_err(RafsError::FillSuperblock)?;
-        let blob_infos = sb.superblock.get_blob_infos();
+        let mut blob_infos = sb.superblock.get_blob_infos();
+
+        // if enable chunk dedup, modify blob's dedup_bitmap.
+        let is_dedup = cfg.dedup.is_some() && cfg.dedup.as_ref().unwrap().enable;
+        if is_dedup {
+            let mut dedup_blobs = vec![];
+            for blob in blob_infos.iter() {
+                let mut blob = blob.deref().clone();
+                let chunk_count = blob.chunk_count() as usize;
+                let mut dedup_bitmap = bitvec!(0; chunk_count);
+                let size = sb.meta.chunk_table_size as usize;
+                let unit_size = size_of::<RafsV5ChunkInfo>();
+                if size % unit_size != 0 {
+                    return Err(RafsError::InvalidImageData);
+                }
+
+                for idx in 0..(size / unit_size) {
+                    let chunk = sb.superblock.get_chunk_info(idx as usize).unwrap();
+                    let chunk_idx = chunk.id() as usize;
+                    if chunk_idx < chunk_count {
+                        dedup_bitmap.set(chunk_idx, chunk.is_deduped());
+                    }
+                }
+                blob.set_dedup_bitmap(Some(dedup_bitmap));
+                dedup_blobs.push(Arc::new(blob));
+            }
+            blob_infos = dedup_blobs;
+        }
+
         let device = BlobDevice::new(cfg, &blob_infos).map_err(RafsError::CreateDevice)?;
 
         if cfg.is_chunk_validation_enabled() && sb.meta.has_inlined_chunk_digest() {

storage/Cargo.toml

@@ -24,7 +24,7 @@ libc = "0.2"
 log = "0.4.8"
 nix = "0.24"
 reqwest = { version = "0.11.14", features = ["blocking", "json"], optional = true }
-serde = { version = "1.0.110", features = ["serde_derive", "rc"] }
+serde = { version = "1.0.137", features = ["derive", "rc"] }
 serde_json = "1.0.53"
 sha1 = { version = "0.10.5", optional = true }
 sha2 = { version = "0.10.2", optional = true }
@@ -35,6 +35,10 @@ url = { version = "2.1.1", optional = true }
 vm-memory = "0.10"
 fuse-backend-rs = "^0.10.3"
 gpt = { version = "3.0.0", optional = true }
+bitvec = { version="1", default-features = false, features = ["alloc",
+  "atomic",
+  "serde",
+  "std",]}
 
 nydus-api = { version = "0.3", path = "../api" }
 nydus-utils = { version = "0.4", path = "../utils", features = ["encryption", "zran"] }

storage/src/cache/cachedfile.rs

@@ -376,11 +376,15 @@ impl FileCacheEntry {
                 extended_chunks[start..=end].to_vec()
             }
         } else {
-            while !extended_chunks.is_empty() {
-                let chunk = &extended_chunks[extended_chunks.len() - 1];
-                if matches!(self.chunk_map.is_ready(chunk.as_ref()), Ok(true)) {
-                    extended_chunks.pop();
-                } else {
+            // check from start to end for dedup
+            for idx in 0..extended_chunks.len() {
+                let chunk = &extended_chunks[idx];
+                if matches!(self.chunk_map.is_ready(chunk.as_ref()), Ok(true))
+                    || self
+                        .blob_info
+                        .get_dedup_by_chunk_idx(chunk.as_ref().id() as usize)
+                {
+                    extended_chunks.truncate(idx);
                     break;
                 }
             }
@@ -591,6 +595,10 @@ impl BlobCache for FileCacheEntry {
                     continue;
                 }
 
+                if self.blob_info.get_dedup_by_chunk_idx(c.id() as usize) {
+                    continue;
+                }
+
                 // For digested chunk map, we must check whether the cached data is valid because
                 // the digested chunk map cannot persist readiness state.
                 let d_size = c.uncompressed_size() as usize;
@@ -606,9 +614,12 @@ impl BlobCache for FileCacheEntry {
                 if let Ok(true) = self.chunk_map.check_ready_and_mark_pending(c.as_ref()) {
                     // The chunk is ready, so skip it.
                     continue;
-                } else {
-                    pending.push(c.clone());
                 }
+                if self.blob_info.get_dedup_by_chunk_idx(c.id() as usize) {
+                    continue;
+                }
+
+                pending.push(c.clone());
             }
         }
 

storage/src/cache/dummycache.rs

@@ -136,6 +136,12 @@ impl BlobCache for DummyCache {
             if !bios[0].user_io {
                 return Ok(0);
             }
+            if self
+                .blob_info
+                .get_dedup_by_chunk_idx(bios[0].chunkinfo.id() as usize)
+            {
+                return Ok(0);
+            }
             let buf = unsafe { std::slice::from_raw_parts_mut(bufs[0].as_ptr(), d_size) };
             self.read_chunk_from_backend(&bios[0].chunkinfo, buf)?;
             return Ok(buf.len());

storage/src/device.rs

@@ -32,6 +32,7 @@ use std::path::Path;
 use std::sync::{Arc, Mutex};
 
 use arc_swap::ArcSwap;
+use bitvec::prelude::*;
 use fuse_backend_rs::api::filesystem::ZeroCopyWriter;
 use fuse_backend_rs::file_buf::FileVolatileSlice;
 use fuse_backend_rs::file_traits::FileReadWriteVolatile;
@@ -180,6 +181,9 @@ pub struct BlobInfo {
     cipher_object: Arc<Cipher>,
     /// Cipher context for encryption.
     cipher_ctx: Option<CipherContext>,
+
+    /// Bitvector to indicate which chunks are deduplicated.
+    dedup_bitmap: Option<BitVec>,
 }
 
 fn serialize_cipher_object<S>(cipher_object: &Arc<Cipher>, serializer: S) -> Result<S::Ok, S::Error>
@@ -270,6 +274,7 @@ impl BlobInfo {
             meta_path: Arc::new(Mutex::new(String::new())),
             cipher_object: Default::default(),
             cipher_ctx: None,
+            dedup_bitmap: None,
         };
 
         blob_info.compute_features();
@@ -622,6 +627,38 @@ impl BlobInfo {
             self.cipher_ctx.clone(),
         )
     }
+
+    pub fn set_dedup_bitmap(&mut self, dedup_bitmap: Option<BitVec>) {
+        self.dedup_bitmap = dedup_bitmap;
+    }
+
+    pub fn set_dedup_by_chunk_idx(&mut self, index: usize, value: bool) {
+        if index >= self.chunk_count as usize || self.dedup_bitmap.is_none() {
+            return;
+        }
+
+        if let Some(bitmap) = &mut self.dedup_bitmap {
+            bitmap.set(index, value);
+        }
+    }
+
+    pub fn get_dedup_by_chunk_idx(&self, index: usize) -> bool {
+        if self.dedup_bitmap.is_none() {
+            return false;
+        }
+        // if chunk index > blob.chunk_count, means this chunk is from other blob.
+        if index >= self.chunk_count as usize {
+            return true;
+        }
+        if let Some(bitmap) = &self.dedup_bitmap {
+            match bitmap.get(index).as_deref() {
+                Some(v) => *v,
+                None => false,
+            }
+        } else {
+            false
+        }
+    }
 }
 
 bitflags! {