Re: [RFC PATCH v1 0/6] Introducing `wq_cpu_set` mount option for btrfs

[Tejun Heo]

On Sun, Feb 26, 2023 at 11:02:53PM +0700, Ammar Faizi wrote:
> Hi,
> 
> This is an RFC patchset that introduces the `wq_cpu_set` mount option.
> This option lets the user specify a CPU set that the Btrfs workqueues
> will use.
> 
> Btrfs workqueues can slow sensitive user tasks down because they can use
> any online CPU to perform heavy workloads on an SMP system. Add a mount
> option to isolate the Btrfs workqueues to a set of CPUs. It is helpful
> to avoid sensitive user tasks being preempted by Btrfs heavy workqueues.
> 
> This option is similar to the taskset bitmask except that the comma
> separator is replaced with a dot. The reason for this is that the mount
> option parser uses commas to separate mount options.

Hmm... the allowed cpumasks for unbounded workqueues can already be set
through /sys/devices/virtual/workqueue/cpumask and also each individual
workqueue can be exposed in the matching subdirectory by setting WQ_SYSFS.
Wouldn't the proposed btrfs option be a bit reduandant?

Thanks.

-- 
tejun