Re: [PATCH v3 2/2] blk-mq: expose tag starvation counts via debugfs

[Jens Axboe]

On 4/17/26 12:28 PM, Bart Van Assche wrote:
> On 3/19/26 3:19 PM, Aaron Tomlin wrote:
>> To guarantee zero performance overhead for production kernels compiled
>> without debugfs, the underlying atomic_t variables and their associated
>> increment routines are strictly guarded behind CONFIG_BLK_DEBUG_FS.
>> When this configuration is disabled, the tracking logic compiles down
>> to a safe no-op.
> 
> I don't think that's sufficient. Please use per-cpu counters to
> minimize the overhead for kernels in which debugfs is enabled.

Agree, this is the usual nonsense of thinking you can hide any overhead
behind a config option, when in practice production kernels very much DO
have CONFIG_DEBUGFS enabled.

-- 
Jens Axboe