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From: Jens Axboe <[email protected]>
To: Jackie Liu <[email protected]>
Cc: [email protected]
Subject: Re: [PATCH v2] io_uring: reduced function parameter ctx if possible
Date: Fri, 8 Nov 2019 07:39:27 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 11/8/19 7:33 AM, Jackie Liu wrote:
> 
> 
> 在 2019/11/8 22:16, Jens Axboe 写道:
>> On 11/8/19 7:11 AM, Jens Axboe wrote:
>>> On 11/8/19 12:29 AM, Jackie Liu wrote:
>>>> Many times, the core of the function is req, and req has already set
>>>> req->ctx at initialization time, so there is no need to pass in from
>>>> outside.
>>>>
>>>> Cleanup, no function change.
>>>
>>> I was curious if this patch netted us any improvements as well, but it
>>> actually blows up the text segment a lot on my laptop. Before the
>>> patch:
>>>
>>>       text	   data	    bss	    dec	    hex	filename
>>>      87504	  17588	    256	 105348	  19b84	fs/io_uring.o
>>>
>>> and after:
>>>
>>>       text	   data	    bss	    dec	    hex	filename
>>>      99098	  17876	    256	 117230	  1c9ee	fs/io_uring.o
>>>
>>> which seems really odd. I double checked just to be sure!
>>>
>>> axboe@x1:~ $ gcc --version
>>> gcc (Ubuntu 9.2.1-17ubuntu1~18.04.1) 9.2.1 20191102
>>
>> I took a look at the generated code, and it looks like it's just
>> enabling gcc to inline a lot more aggressively.
>>
> 
> Hum... I don't have a lot of attention to the size of the generated
> code, just to make the code look easier to understand. Will this affect
> performance?

Seems to be an extreme case on the laptop since I have various debug
options enabled for testing in qemu, but it's an increase on my
test box with gcc 7.2 as well. I don't think it's anything to worry
about, it's just inlining what it should inline. I did a quick perf
run and we're not down, so I'm going to apply this one as it cleans
up the code and that's always the most important.

-- 
Jens Axboe


  parent reply	other threads:[~2019-11-08 14:39 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08  7:29 [PATCH v2] io_uring: reduced function parameter ctx if possible Jackie Liu
2019-11-08  9:00 ` Jackie Liu
2019-11-08  9:10   ` Bob Liu
     [not found]     ` <[email protected]>
2019-11-08  9:24       ` Jackie Liu
2019-11-08  9:35         ` Bob Liu
2019-11-08 14:11 ` Jens Axboe
2019-11-08 14:16   ` Jens Axboe
     [not found]     ` <[email protected]>
2019-11-08 14:39       ` Jens Axboe [this message]
     [not found]         ` <[email protected]>
2019-11-08 14:47           ` Jens Axboe

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