Re: [PATCH -next RFC v3 0/8] improve tag allocation under heavy load

[Bart Van Assche <bvanassche@acm.org>]

On 4/15/22 03:10, Yu Kuai wrote:
> The single io performance(randwrite):
> 
> | bs       | 128k | 256k | 512k | 1m   | 1280k | 2m   | 4m   |
> | -------- | ---- | ---- | ---- | ---- | ----- | ---- | ---- |
> | bw MiB/s | 20.1 | 33.4 | 51.8 | 67.1 | 74.7  | 82.9 | 82.9 |

Although the above data is interesting, it is not sufficient. The above 
data comes from a setup with a single hard disk. There are many other 
configurations that are relevant (hard disk array, high speed NVMe, QD=1 
USB stick, ...) but for which no conclusions can be drawn from the above 
data.

Another question is whether the approach of this patch series is the 
right approach? I would expect that round-robin wakeup of waiters would 
be ideal from a fairness point of view. However, there are patches in 
this patch series that guarantee that wakeup of tag waiters won't happen 
in a round robin fashion.

Thanks,

Bart.