LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Chao Yu <yuchao0@huawei.com>
To: dsterba@suse.cz, "Dan Carpenter" <dan.carpenter@oracle.com>,
	"Gao Xiang" <gaoxiang25@huawei.com>,
	devel@driverdev.osuosl.org,
	"Sasha Levin" <alexander.levin@microsoft.com>,
	"Valdis Klētnieks" <valdis.kletnieks@vt.edu>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org,
	"Christoph Hellwig" <hch@infradead.org>,
	linux-fsdevel@vger.kernel.org,
	"OGAWA Hirofumi" <hirofumi@mail.parknet.co.jp>
Subject: Re: [PATCH] staging: exfat: add exfat filesystem code to staging
Date: Sat, 31 Aug 2019 11:50:21 +0800
Message-ID: <29d7e697-3d74-bc0e-a756-713f682c32ff@huawei.com> (raw)
In-Reply-To: <20190830115142.GM2752@twin.jikos.cz>

On 2019/8/30 19:51, David Sterba wrote:
> On Fri, Aug 30, 2019 at 10:06:25AM +0800, Chao Yu wrote:
>> On 2019/8/29 23:43, Dan Carpenter wrote:
>>>> p.s. There are 2947 (un)likely places in fs/ directory.
>>>
>>> I was complaining about you adding new pointless ones, not existing
>>> ones.  The likely/unlikely annotations are supposed to be functional and
>>> not decorative.  I explained this very clearly.
>>>
>>> Probably most of the annotations in fs/ are wrong but they are also
>>> harmless except for the slight messiness.  However there are definitely
>>> some which are important so removing them all isn't a good idea.
>>
>> Hi Dan,
>>
>> Could you please pick up one positive example using likely and unlikely
>> correctly? so we can follow the example, rather than removing them all blindly.
> 
> Remove all of them and re-add with explanation if and how each is going
> to make things better. If you can't reason about, prove by benchmarks or
> point to inefficient asm code generated, then don't add them again.

It seems the result of it is strongly related to arch and compiler, if we readd
it after we just prove its gain only in one combination, I doubt we may suffer
regression in other combination in between archs and comilers. It looks like we
don't have any cheaper way to readd it? instead of verifying all/most combinations.

> 
> The feedback I got from CPU and compiler people over the years is not to
> bother using the annotations. CPUs are doing dynamic branch prediction
> and compilers are applying tons of optimizations.
> 
> GCC docs state about the builtin: "In general, you should prefer to use
> actual profile feedback for this (-fprofile-arcs), as programmers are
> notoriously bad at predicting how their programs actually perform."
> (https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html)

Yes, I agree with this. Thanks a lot for sharing your experience. :)

The removal change has done and been merged into Greg's tree, let's consider to
readd it later if possible as you suggested.

thanks,

> .
> 

  reply index

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-28 16:08 Greg Kroah-Hartman
2019-08-28 17:00 ` Greg Kroah-Hartman
2019-08-29  6:23   ` Christoph Hellwig
2019-08-29  6:39     ` Greg Kroah-Hartman
2019-08-29  9:41       ` Christoph Hellwig
2019-08-29  9:50         ` Greg Kroah-Hartman
2019-08-29 10:37           ` Christoph Hellwig
2019-08-29 11:04             ` Gao Xiang
2019-08-29 11:18               ` Greg Kroah-Hartman
2019-08-29 11:18             ` Greg Kroah-Hartman
2019-08-29 15:11               ` Dan Carpenter
2019-08-29 15:27                 ` Gao Xiang
2019-08-29 15:43                   ` Dan Carpenter
2019-08-29 15:51                     ` Gao Xiang
2019-08-29 16:04                       ` Gao Xiang
2019-08-30  8:34                         ` Dan Carpenter
2019-08-30  8:43                           ` Gao Xiang
2019-08-30 11:26                             ` Dan Carpenter
2019-08-30 12:04                               ` Gao Xiang
2019-08-29 16:44                     ` Gao Xiang
2019-08-29 16:59                       ` Joe Perches
2019-08-29 17:02                         ` Gao Xiang
2019-08-30  2:06                     ` Chao Yu
2019-08-30  6:38                       ` Gao Xiang
2019-08-30 12:00                         ` Checking usage of likeliness annotations Markus Elfring
2019-08-30 11:51                       ` [PATCH] staging: exfat: add exfat filesystem code to staging David Sterba
2019-08-31  3:50                         ` Chao Yu [this message]
2019-08-30 15:36               ` Christoph Hellwig
2019-08-30 21:54               ` Dave Chinner
2019-08-31 10:31                 ` Valdis Klētnieks
2019-09-01  0:04                   ` Dave Chinner
2019-08-29  7:01     ` Gao Xiang
2019-08-29  8:24       ` Gao Xiang
2019-08-29  9:51         ` Christoph Hellwig
2019-08-29 12:14 ` Pali Rohár
2019-08-29 12:34   ` Valdis Klētnieks
2019-08-29 12:46     ` Pali Rohár
2019-08-29 14:08 ` Markus Elfring
2019-08-29 15:44 ` Markus Elfring
2019-08-29 20:56 ` Pali Rohár
2019-08-29 23:18   ` Valdis Klētnieks
2019-08-29 23:35     ` Sasha Levin
2019-08-30  7:56       ` Pali Rohár
2019-10-16 14:03         ` Pali Rohár
2019-10-16 14:31           ` Sasha Levin
2019-10-16 16:03             ` Pali Rohár
2019-10-16 16:20               ` Sasha Levin
2019-10-16 16:22               ` Greg Kroah-Hartman
2019-10-16 16:32                 ` Pali Rohár
2019-10-16 16:50                   ` Greg Kroah-Hartman
2019-10-16 20:33               ` Sasha Levin
2019-10-16 21:53                 ` Valdis Klētnieks
2019-10-17  7:53                   ` Pali Rohár
2019-10-17  7:50                 ` Pali Rohár
2019-10-16 16:05             ` Valdis Klētnieks
2019-08-30  8:03     ` Pali Rohár
2019-08-30 15:40   ` Christoph Hellwig
2019-08-30 15:43     ` Pali Rohár
2019-09-14 13:39 ` [PATCH] staging: exfat: add exfat filesystem code to Park Ju Hyung
2019-09-15 13:54   ` Greg KH
2019-09-15 16:11     ` Ju Hyung Park
     [not found] ` <20190918195920.25210-1-qkrwngud825@gmail.com>
2019-09-18 20:12   ` [PATCH] staging: exfat: rebase to sdFAT v2.2.0 Greg KH
2019-09-18 20:13   ` Greg KH
2019-09-18 20:22     ` Ju Hyung Park
2019-09-18 20:26       ` Greg KH
2019-09-18 20:31         ` Ju Hyung Park
2019-09-18 20:46           ` Valdis Klētnieks
2019-09-18 21:31   ` kbuild test robot
2019-09-18 21:31   ` kbuild test robot
2019-09-18 22:17     ` Ju Hyung Park

Reply instructions:

You may reply publically 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=29d7e697-3d74-bc0e-a756-713f682c32ff@huawei.com \
    --to=yuchao0@huawei.com \
    --cc=alexander.levin@microsoft.com \
    --cc=dan.carpenter@oracle.com \
    --cc=devel@driverdev.osuosl.org \
    --cc=dsterba@suse.cz \
    --cc=gaoxiang25@huawei.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=hch@infradead.org \
    --cc=hirofumi@mail.parknet.co.jp \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=valdis.kletnieks@vt.edu \
    /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

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org linux-kernel@archiver.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox