Messages in this thread | | | Date | Tue, 1 Mar 2022 00:30:01 -0300 | From | Enzo Matsumiya <> | Subject | Re: [PATCH] nvme-pci: trigger disk activity LED |
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On 02/28, Jens Axboe wrote: >On 2/28/22 2:22 AM, Christoph Hellwig wrote: >> I don't think we should add code to the absolutel fast path for >> blinkenlights. > >Agree. It'd be a lot better to put the cost on the led trigger >side, and not need anything in the fast path for block devices. >Monitor disk stats, or something like that.
There's been at least 4 attempts to do so, as far as I'm aware (one of them being mine). All got rejected due to the complexity it introduced, that's how I ended up with this one-liner.
Performance-wise, I'm understand the problems, but according to ftrace, ledtrig_disk_activity() adds an average of 0.2us overhead, whether an LED is assigned or not. Is that really unacceptable?
If so, would introducing a CONFIG_NVME_LED (default =n) and wrap that call around it make it better? Then at least there's a chance to inform users that desires this feature about performance costs.
Cheers,
Enzo
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