Tag: redo

Xfce 4.18 出版

看到「Xfce 4.18 released」這個消息，可以放一個月讓 bug 飛一飛改一改再來更新...

看起來 thunar (Xfce 的檔案總管？) 改了不少東西，可以看到花了很多篇幅在介紹。看起來對我來說最有改變的是 undo 與 redo 的部份：

It is now possible to undo basic file operations and to redo them. Undo and Redo can be used for 'move', 'rename', 'trash', 'link' and 'create' operations. Per default, a history of the last 10 operations is stored, though the history length is configurable. Whenever an Undo/Redo is triggered, a notification with few details will be shown.

其他的應該是還好...

InnoDB redo log 大小對效能的影響

在「Benchmark(et)ing with InnoDB redo log size」這邊看到在討論 InnoDB redo log 的大小對效能的影響 (也就是 innodb_log_file_size 與 innodb_log_files_in_group)。

開頭就有先提到重點，在新版 MySQL 裡，幾乎所有的情況比較大的 redo log 有比較好的效能 (平均值)：

tl;dr - conclusions specific to my test

  1. A larger redo log improves throughput
  2. A larger redo log helps more with slower storage than with faster storage because page writeback is more of a bottleneck with slower storage and a larger redo log reduces writeback.
  3. A larger redo log can help more when the working set is cached because there are no stalls from storage reads and storage writes are more likely to be a bottleneck.
  4. InnoDB in MySQL 5.7.17 is much faster than 5.6.35 in all cases except IO-bound + fast SSD

可以看出來平均效能的提昇很顯著，不管是增加 redo log 大小還是升級到 5.7：

但作者也遇到了奇怪的效能問題。雖然平均效能提昇得很顯著，但隨著加入資料的增加，效能的 degradation 其實很嚴重，在原來的網頁上可以看到這些資訊。

The results above show average throughput and that hides a lot of interesting behavior. We expect throughput over time to not suffer from variance -- for both InnoDB and for MyRocks. For many of the results below there is a lot of variance (jitter).

所以也許現階段先加大就好 (至少寫入的效能會提昇)，不需要把這個特性當作升級 MySQL 的理由。