# journal

**Repository Path**: ziyanzhang/journal

## Basic Information

- **Project Name**: journal
- **Description**: No description available
- **Primary Language**: Unknown
- **License**: GPL-2.0
- **Default Branch**: zjournal
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2023-12-21
- **Last Updated**: 2024-05-29

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# Z-Journal

---

All added files comply with the license rules of the Linux kernel.

## Introduction

---

File system journaling critically limits the scalability of a file system because all simultaneous write operations coming from multiple cores must be serialized to be written to the journal area. Although a few scalable journaling approaches have been proposed, they required the radical redesign of file systems, or tackled only a part of the scalability bottlenecks. Per-core journaling, in which a core has its own journal stack, can clearly provide scalability. However, it requires a journal coherence mechanism because two or more cores can write to a shared file system block, so write order on the shared block must be preserved across multiple journals. In this paper, we propose a novel scalable per-core journal design. The proposed design allows a core to commit independently to other cores. The journal transactions involved in shared blocks are linked together through order-preserving transaction chaining to form a transaction order graph. The ordering constraints later will be imposed during the checkpoint process. Because the proposed design is self-contained in the journal layer and does not rely on the file system, its implementation, Z-Journal, can easily replace JBD2, the generic journal layer. Our evaluation with FxMark, SysBench and Filebench running on the ext4 file system in an 80-core server showed that it outperformed the current JBD2 by up to approx. 4000 %.

## The guide to using Z-Journal

---

- Download and build e2fsprocs for zjournal.

```
git clone https://github.com/J-S-Kim/e2fsprog-zj.git
cd e2fsprog-zj
./configure
make
```

- Download and install the kernel of the current repository, and reboot to the kernel you installed.
- When installing, configure should be set as below.
- After rebooting, verify that ext4mj and zj modules are installed successfully.

```
File systems  --->
    [M] The Extended 4 (ext4mj) filesystem
```

- Format the storage device and mount it with the command shown below.
- At this point, the number of journals is the same as the current number of online cores.

```
sudo ./e2fsprog-zj/misc/mke2fs -t ext4 -J multi_journal -F -G 1 /dev/<block device>
sudo ./e2fsprog-zj/misc/tune2fs -o journal_data /dev/<block device>
sudo mount -t ext4mj /dev/<block device> <mount point>
```

## The guide to develop Z-Journal

---

- Z-Journal mainly modified transaction.c, commit.c, and checkpoint.c of the fs/zj directory, and super.c, fsync.c, mballoc.c, ext4mj_zj.c, ext4mj_zj.h of the fs/ext4mj directory.

### About journal modification
- The contents of Journal Coherence Commit are reflected in commit.c and transaction.c.
- The contents of Journal Coherence Checkpoint are reflected in checkpoint.c

### About file system modification
- Modification of super.c is necessary to recognize multiple journals, and ext4mj_zj files are necessary for good comfort with existing journaling APIs.
- _fsync_ proceeds in a different way than before due to the per-core journaling. Therefore, the fsync.c file was modified.
- The mballoc file includes modification of core-aware block group allocation (BGA).

---

## Evaluation

### Environment
![environment](https://user-images.githubusercontent.com/17569303/138211561-ebf1ccc2-fe70-4e04-a810-34a2d0fbb953.png)

### FileBench results

* Fileserver

![fileserver](https://user-images.githubusercontent.com/17569303/138212007-a36f8654-611d-47c6-98b7-ddb5c28d6c2a.jpg)

* Varmail

![varmail](https://user-images.githubusercontent.com/17569303/138212016-7c1ba74d-aa91-4b9e-bfec-a8f800e85d94.jpg)