1. buffer=4096 is better for Writes of more than PIPE_BUF bytes may be nonatomic
2. flush=1. Since the log buffer is lowered, the flush time should also be lowered.

hi, I also made a test.

```
4096  Requests/sec:  16079.75
8192 Requests/sec:  16389.52
16384 Requests/sec:  16395.30
32768 Requests/sec:  16459.71
```
I think a log buffer size of 8192 or 16384 would be appropriate.

On the other hand, the refresh time of 3 seconds is still relatively long, and 1 or 3 seconds doesn't particularly affect QPS.

So I also agree with `buffer=16384 flush=1; `