linux-kernel - Re: Re: [PATCH liburing] test: add test cases for hybrid iopoll

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Message-ID: <20241115033445.742464-1-xue01.he@samsung.com>
Date: Fri, 15 Nov 2024 11:34:45 +0800
From: hexue <xue01.he@...sung.com>
To: axboe@...nel.dk
Cc: asml.silence@...il.com, io-uring@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH liburing] test: add test cases for hybrid iopoll

>On 11/13/24 10:03 PM, hexue wrote:
>> diff --git a/man/io_uring_setup.2 b/man/io_uring_setup.2
>> index 2f87783..fa928fa 100644
...
>
>This flag must be used with
>
>> +.B IORING_SETUP_IOPOLL
>> +flag. hybrid poll is a new
>
>Like before, skip new. Think about what happens when someone reads this
>in 5 years time. What does new mean? Yes it may be new now, but docs
>are supposed to be timeless.
>
>> +feature baed on iopoll, this could be a suboptimal solution when running
>
>based on
>
>> +on a single thread, it offers higher performance than IRQ and lower CPU
>> +utilization than polling. Similarly, this feature also requires the devices
>> +to support polling configuration.
>
>This doesn't explain how it works. I'd say something like:
>
>Hybrid io polling differs from strict polling in that it will delay a
>bit before doing completion side polling, to avoid wasting too much CPU.
>Like IOPOLL, it requires that devices support polling.

Thanks, will change the description.

...

>> +		return -EINVAL;
>> +

>The kernel should already do this, no point duplicating it in liburing.
>
>The test bits look much better now, way simpler. I'll just need to
>double check that they handle EINVAL on setup properly, and EOPNOTSUPP
>at completion time will turn off further testing of it. Did you run it
>on configurations where hybrid io polling will both fail at setup time,
>and at runtime (eg the latter where the kernel supports it, but the
>device/fs does not)?

Yes, I have run both of these error configurations. The running cases are: 
hybrid poll without IORING_SETUP_IOPOLL and device with incorrect queue
configuration, EINVAL and EOPNOTSUPP are both identified.

--
hexue