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From: Bart Van Assche <bvanassche@acm.org>
To: Aaron Tomlin <atomlin@atomlin.com>,
	axboe@kernel.dk, rostedt@goodmis.org, mhiramat@kernel.org,
	mathieu.desnoyers@efficios.com
Cc: johannes.thumshirn@wdc.com, kch@nvidia.com, dlemoal@kernel.org,
	ritesh.list@gmail.com, loberman@redhat.com, neelx@suse.com,
	sean@ashe.io, mproche@gmail.com, chjohnst@gmail.com,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-trace-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/2] blk-mq: expose tag starvation counts via debugfs
Date: Fri, 17 Apr 2026 11:28:53 -0700	[thread overview]
Message-ID: <ac8d9fd1-15c6-44cf-ba5a-85bd4aefce9b@acm.org> (raw)
In-Reply-To: <20260319221956.332770-3-atomlin@atomlin.com>

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.

Thanks,

Bart.

  parent reply	other threads:[~2026-04-17 18:29 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-03-19 22:19 [PATCH v3 0/2] blk-mq: introduce tag starvation observability Aaron Tomlin
2026-03-19 22:19 ` [PATCH v3 1/2] blk-mq: add tracepoint block_rq_tag_wait Aaron Tomlin
2026-03-19 22:19 ` [PATCH v3 2/2] blk-mq: expose tag starvation counts via debugfs Aaron Tomlin
2026-03-20 15:08   ` Laurence Oberman
2026-04-17 18:28   ` Bart Van Assche [this message]
2026-04-17 20:16     ` Jens Axboe
2026-04-18  2:29       ` Aaron Tomlin
2026-04-17 18:15 ` [PATCH v3 0/2] blk-mq: introduce tag starvation observability Aaron Tomlin

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