Re: [PATCHSET v2 0/5] Enable alloc caching and batched freeing for passthrough

From: Jens Axboe <axboe@kernel.dk>
To: Anuj gupta <anuj1072538@gmail.com>
Cc: linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
	linux-nvme@lists.infradead.org
Subject: Re: [PATCHSET v2 0/5] Enable alloc caching and batched freeing for passthrough
Date: Wed, 28 Sep 2022 08:22:20 -0600	[thread overview]
Message-ID: <45fef5c6-8945-a140-a3ce-34bb4b287dc4@kernel.dk> (raw)
In-Reply-To: <CACzX3AumYMDVPwvRYpMi6vvcPTzR0W0bUT1-545HvArpH+7Uwg@mail.gmail.com>

On 9/28/22 7:23 AM, Anuj gupta wrote:
> On Tue, Sep 27, 2022 at 7:14 AM Jens Axboe <axboe@kernel.dk> wrote:
>>
>> Hi,
>>
>> The passthrough IO path currently doesn't do any request allocation
>> batching like we do for normal IO. Wire this up through the usual
>> blk_mq_alloc_request() allocation helper.
>>
>> Similarly, we don't currently supported batched completions for
>> passthrough IO. Allow the request->end_io() handler to return back
>> whether or not it retains ownership of the request. By default all
>> handlers are converted to returning RQ_END_IO_NONE, which retains
>> the existing behavior. But with that in place, we can tweak the
>> nvme uring_cmd end_io handler to pass back ownership, and hence enable
>> completion batching for passthrough requests as well.
>>
>> This is good for a 10% improvement for passthrough performance. For
>> a non-drive limited test case, passthrough IO is now more efficient
>> than the regular bdev O_DIRECT path.
>>
>> Changes since v1:
>> - Remove spurious semicolon
>> - Cleanup struct nvme_uring_cmd_pdu handling
>>
>> --
>> Jens Axboe
>>
>>
> I see an improvement of ~12% (2.34 to 2.63 MIOPS) with polling enabled and
> an improvement of ~4% (1.84 to 1.92 MIOPS) with polling disabled using the
> t/io_uring utility (in fio) in my setup with this patch series!

Thanks for your testing! I'll add your reviewed-by to the series.

-- 
Jens Axboe