All of lore.kernel.org
 help / color / mirror / Atom feed
From: Chen Gang <chengang@emindsoft.com.cn>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: dhowells@redhat.com, akpm@linux-foundation.org,
	nicolas.iooss_linux@m4x.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] fs: dcache: Use bool return value instead of int
Date: Thu, 14 Jan 2016 06:39:53 +0800	[thread overview]
Message-ID: <5696D239.2000605@emindsoft.com.cn> (raw)
In-Reply-To: <20160112222105.GT17997@ZenIV.linux.org.uk>


On 1/13/16 06:21, Al Viro wrote:
> On Wed, Jan 13, 2016 at 05:42:20AM +0800, Chen Gang wrote:
> 
>> For me, it really generates a little better code:
>>
>>  - Both 1-word store and 1-byte store are 1 instruction, normally, they
>>    have the same execution speed (although it is not quite precise).
>>
>>  - But 1-byte store instruction has short length under CISC archs, which
>>    can generate a little better code globally.
>>
>>  - For most of archs, 1-word store can process bytes nonalignment cases,
>>    for check_mount() individually, the parameter data may be not word
>>    alignment, which may cause the 1-word store slower than 1-byte store.
> 
> What the hell do you mean, unaligned?  It's given an address of local
> variable of type int; it _will_ be aligned, or the compiler is FUBAR.
> 

I guess you misunderstand my meaning, in our case, it should not happen,
so I say "for check_mount() individually".

For 32 bits store instruction, we need consider about the byte alignment.

> As for the inlines... frankly, if gcc generates a different code from having
> replaced int with bool in those, it's time to do something very nasty to
> gcc developers.
> 

Could you provide the related proof?

Thanks.
-- 
Chen Gang (陈刚)

Open, share, and attitude like air, water, and life which God blessed

  reply	other threads:[~2016-01-13 22:37 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-11 21:30 [PATCH] fs: dcache: Use bool return value instead of int chengang
2016-01-11 22:51 ` Al Viro
2016-01-12 21:42   ` Chen Gang
2016-01-12 22:21     ` Al Viro
2016-01-13 22:39       ` Chen Gang [this message]
2016-01-13 22:54         ` Al Viro
2016-01-14 15:39           ` Chen Gang
2016-01-24 21:19             ` Chen Gang
2016-01-24 21:27               ` Al Viro
2016-01-25 21:24                 ` Chen Gang
2016-01-12  0:33 ` David Howells
2016-01-12  1:02   ` Al Viro

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=5696D239.2000605@emindsoft.com.cn \
    --to=chengang@emindsoft.com.cn \
    --cc=akpm@linux-foundation.org \
    --cc=dhowells@redhat.com \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=nicolas.iooss_linux@m4x.org \
    --cc=viro@ZenIV.linux.org.uk \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.