On Thu, Jan 23, 2020 at 10:28:47PM -0800, Colin Zou wrote: > > I used to run my application on ext3 on SSD and recently switched to > ext4. However, my application sees performance regression. The root > cause is, iosnoop shows that the workload includes a lot of fsync and > every fsync does data IO and also jbd2 IO. While on ext3, it seldom > does journal IO. Is there a way to tune ext4 to increase fsync > performance? Say, by reducing jbd2 IO requests? If you're not seeing journal I/O from ext3 after an fsync, you're not looking at things correctly. At the very *least* there will be journal I/O for the commit block, unless all of the work was done earlier in a previous journal commit. In general, ext4 and ext3 will be doing roughly the same amount of I/O to the journal. In some cases, depending on the workload, ext4 *might* need to do more data I/O for the file being synced. That's because with ext3, if there is an intervening periodic 5 second journal commit, some or all of the data I/O may have been forced out to disk earlier due to said 5 second sync. What sort of workload does your application do? How much data blocks are you writing before each fsync(), and how often are the fsync() operations? - Ted
