From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f199.google.com (mail-io0-f199.google.com [209.85.223.199]) by kanga.kvack.org (Postfix) with ESMTP id 268F16B0005 for ; Wed, 13 Jul 2016 10:26:27 -0400 (EDT) Received: by mail-io0-f199.google.com with SMTP id m101so97337833ioi.0 for ; Wed, 13 Jul 2016 07:26:27 -0700 (PDT) Received: from out4434.biz.mail.alibaba.com (out4434.biz.mail.alibaba.com. [47.88.44.34]) by mx.google.com with ESMTP id y6si922609ota.92.2016.07.13.07.26.25 for ; Wed, 13 Jul 2016 07:26:26 -0700 (PDT) Date: Wed, 13 Jul 2016 22:26:08 +0800 From: "=?UTF-8?B?6ZmI5Yia?=" Reply-To: "=?UTF-8?B?6ZmI5Yia?=" Message-ID: Subject: =?UTF-8?B?5Zue5aSN77yaW1BBVENIXSBtbTogbWlncmF0ZTogVXNlIGJvb2wgaW5zdGVhZCBvZiBpbnQg?= =?UTF-8?B?Zm9yIHRoZSByZXR1cm4gdmFsdWUgb2YgUGFnZU1vdmFibGU=?= MIME-Version: 1.0 References: <1468079704-5477-1-git-send-email-chengang@emindsoft.com.cn> <20160711002605.GD31817@bbox> <5783F7DE.9020203@emindsoft.com.cn> <20160712074841.GE14586@dhcp22.suse.cz> <57851FC4.4000000@emindsoft.com.cn>,20160713075346.GC28723@dhcp22.suse.cz In-Reply-To: 20160713075346.GC28723@dhcp22.suse.cz Content-Type: multipart/alternative; boundary="----=ALIBOUNDARY_65200_4fe2a940_57864f80_a33df" Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Minchan Kim , akpm , vbabka , mgorman , "gi-oh.kim" , "iamjoonsoo.kim" , "hillf.zj" , rientjes , linux-mm , linux-kernel , Chen Gang ------=ALIBOUNDARY_65200_4fe2a940_57864f80_a33df Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: base64 SGVsbG86CkV4Y3VzZSBtZSwgSSBoYXZlIHRvIG92ZXIgdGltZSB3b3JrLCBhbmQgd2lsbCBub3Qg Z28gYmFjayBob21lIHVudGlsIHRoaXMgd2VlayBlbmQuQW5kIEkgc2hhbGwgcmVwbHkgaW4gdGhp cyB3ZWVrIGVuZC4KVGhhbmtzLgoKLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0t LS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0t5Y+R5Lu25Lq677yaTWljaGFsIEhvY2tvIDxt aG9ja29Aa2VybmVsLm9yZz7lj5HpgIHml7bpl7TvvJoyMDE25bm0N+aciDEz5pelKOaYn+acn+S4 iSkgMTU6NTPmlLbku7bkurrvvJrpmYjliJogPGNoZW5nYW5nQGVtaW5kc29mdC5jb20uY24+5oqE 44CA6YCB77yaTWluY2hhbiBLaW0gPG1pbmNoYW5Aa2VybmVsLm9yZz47IGFrcG0gPGFrcG1AbGlu dXgtZm91bmRhdGlvbi5vcmc+OyB2YmFia2EgPHZiYWJrYUBzdXNlLmN6PjsgbWdvcm1hbiA8bWdv cm1hbkB0ZWNoc2luZ3VsYXJpdHkubmV0PjsgZ2ktb2gua2ltIDxnaS1vaC5raW1AcHJvZml0YnJp Y2tzLmNvbT47IGlhbWpvb25zb28ua2ltIDxpYW1qb29uc29vLmtpbUBsZ2UuY29tPjsgaGlsbGYu emogPGhpbGxmLnpqQGFsaWJhYmEtaW5jLmNvbT47IHJpZW50amVzIDxyaWVudGplc0Bnb29nbGUu Y29tPjsgbGludXgtbW0gPGxpbnV4LW1tQGt2YWNrLm9yZz47IGxpbnV4LWtlcm5lbCA8bGludXgt a2VybmVsQHZnZXIua2VybmVsLm9yZz47IENoZW4gR2FuZyA8Z2FuZy5jaGVuLjVpNWpAZ21haWwu Y29tPuS4u+OAgOmimO+8mlJlOiBbUEFUQ0hdIG1tOiBtaWdyYXRlOiBVc2UgYm9vbCBpbnN0ZWFk IG9mIGludCBmb3IgdGhlIHJldHVybiB2YWx1ZSBvZiBQYWdlTW92YWJsZQpPbsKgV2VkwqAxMy0w Ny0xNsKgMDA6NTA6MTIswqBDaGVuwqBHYW5nwqB3cm90ZToKPsKgCj7CoAo+wqBPbsKgNy8xMi8x NsKgMTU6NDgswqBNaWNoYWzCoEhvY2tvwqB3cm90ZToKPsKgPsKgT27CoFR1ZcKgMTItMDctMTbC oDAzOjQ3OjQyLMKgQ2hlbsKgR2FuZ8Kgd3JvdGU6Cj7CoD7CoFsuLi5dCj7CoD4+wqBJbsKgb3Vy wqBjYXNlLMKgdGhlwqAywqBvdXRwdXTCoHNpemXCoGFyZcKgc2FtZSzCoGJ1dMKgdW5kZXLCoHg4 Nl82NCzCoHRoZcKgaW5zbnPCoGFyZQo+wqA+PsKgZGlmZmVyZW50LsKgQWZ0ZXLCoHVzZXPCoGJv b2wswqBpdMKgdXNlc8KgcHVzaC9wb3DCoGluc3RlYWTCoG9mwqBicmFuY2gswqBmb3LCoG1lLAo+ wqA+PsKgaXTCoHNob3VsZMKgYmXCoGHCoGxpdHRsZcKgYmV0dGVywqBmb3LCoGNhdGNoaW5nLgo+ wqA+wqAKPsKgPsKgVGhlwqBjb2RlwqBnZW5lcmF0ZWTCoGZvcsKgYm9vbMKgdmVyc2lvbsKgbG9v a3PCoG11Y2jCoHdvcnNlLsKgTG9va8KgYXTCoHRoZcKgZmFzdAo+wqA+wqBwYXRoLsKgR2NjwqB0 cmllc8KgdG/CoHJldXNlwqB0aGXCoHJldHHCoGZyb23CoHRoZcKgZmFzdMKgcGF0aMKgaW7CoHRo ZcKgYm9vbMKgY2FzZQo+wqA+wqBhbmTCoHNvwqBpdMKgaGFzwqB0b8KgcHVzaMKgcmJwwqBhbmTC oHJieMKgb27CoHRoZcKgc3RhY2suCj7CoD7CoAo+wqA+wqBUaGF0wqBiZWluZ8Kgc2FpZCzCoGdj Y8KgZG9lc24ndMKgc2VlbcKgdG/CoGdlbmVyYXRlwqBhwqBiZXR0ZXLCoGNvZGXCoGZvcsKgYm9v bMKgc28KPsKgPsKgScKgZG/CoG5vdMKgdGhpbmvCoHRoaXPCoGlzwqByZWFsbHnCoHdvcnRowqBp dC4KPsKgPgo+wqAKPsKgVGhlwqBjb2RlwqBiZWxvd8KgYWxzb8KgbWVyZ2XCoDPCoHN0YXRlbWVu dHPCoGludG/CoDHCoHJldHVybsKgc3RhdGVtZW50LMKgYWx0aG91Z2gKPsKgZm9ywqBtZSzCoGl0 wqBpc8KgYcKgbGl0dGxlwqBtb3JlwqByZWFkYWJsZSzCoGl0wqB3aWxswqBnZW5lcmF0ZcKgYcKg bGl0dGxlwqBiYWTCoGNvZGUuCj7CoFRoYXTCoGlzwqB0aGXCoHJlYXNvbsKgd2h5wqB0aGXCoG91 dHB1dMKgbG9va3PCoGHCoGxpdHRsZcKgYmFkLgo+wqAKPsKgSW7CoG91csKgY2FzZSzCoGZvcsKg Z2NjwqA2LjAswqB1c2luZ8KgYm9vbMKgaW5zdGVhZMKgb2bCoGludMKgZm9ywqBib29swqBmdW5j dGlvbgo+wqB3aWxswqBnZXTCoHRoZcKgc2FtZcKgb3V0cHV0wqB1bmRlcsKgeDg2XzY0LgoKSWbC oHRoZcKgb3V0cHV0wqBpc8Kgc2FtZcKgdGhlbsKgdGhlcmXCoGlzwqBub8KgcmVhc29uwqB0b8Kg Y2hhbmdlwqBpdC4KCj7CoEluwqBvdXLCoGNhc2UswqBmb3LCoGdjY8KgNC44LMKgdXNpbmfCoGJv b2zCoGluc3RlYWTCoG9mwqBpbnTCoGZvcsKgYm9vbMKgZnVuY3Rpb24KPsKgd2lsbMKgZ2V0wqBh wqBsaXR0bGXCoGJldHRlcsKgb3V0cHV0wqB1bmRlcsKgeDg2XzY0LgoKScKgaGFkwqBhwqBkaWZm ZXJlbnTCoGltcHJlc3Npb27CoGFuZMKgdGhlwqBmYXN0wqBwYXRowqBjb2RlwqBoYWTCoG1vcmUK aW5zdHJ1Y3Rpb25zLsKgQnV0wqBhbnl3YXkswqBpc8KgdGhlcmXCoHJlYWxsecKgYcKgc3Ryb25n wqByZWFzb27CoHRvwqBjaGFuZ2UKdGhvc2XCoHJldHVybsKgdmFsdWVzwqBpbsKgdGhlwqBmaXJz dMKgcGxhY2U/wqBJc24ndMKgdGhhdMKganVzdMKgYcKgcG9pbnRsZXNzwqBjb2RlCmNodXJuPwot LcKgCk1pY2hhbMKgSG9ja28KU1VTRcKgTGFicwo= ------=ALIBOUNDARY_65200_4fe2a940_57864f80_a33df Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hello:

=
Excuse me, I have to over time work, an= d will not go back home until this week end.
And I shall reply in this week end.

Thanks.

--------------------------------= ----------------------------------
=E5=8F=91=E4=BB=B6=E4=BA=BA=EF=BC=9AMichal Hocko <mhocko@kernel.org= >
=E5=8F=91=E9=80=81=E6=97= =B6=E9=97=B4=EF=BC=9A2016=E5=B9=B47=E6=9C=8813=E6=97=A5(=E6=98=9F=E6=9C=9F=E4=B8= =89) 15:53
=E6=94=B6=E4=BB=B6= =E4=BA=BA=EF=BC=9A=E9=99=88=E5=88=9A <chengang@emindsoft.com.cn><= /div>
=E6=8A=84=E3=80=80=E9=80=81=EF=BC=9A= Minchan Kim <minchan@kernel.org>; akpm <akpm@linux-foundation.org>= ; vbabka <vbabka@suse.cz>; mgorman <mgorman@techsingularity.net>; = gi-oh.kim <gi-oh.kim@profitbricks.com>; iamjoonsoo.kim <iamjoonsoo.ki= m@lge.com>; hillf.zj <hillf.zj@alibaba-inc.com>; rientjes <rientje= s@google.com>; linux-mm <linux-mm@kvack.org>; linux-kernel <linux-= kernel@vger.kernel.org>; Chen Gang <gang.chen.5i5j@gmail.com><= /div>
=E4=B8=BB=E3=80=80=E9=A2=98=EF=BC=9A= Re: [PATCH] mm: migrate: Use bool instead of int for the return value of PageM= ovable

On=  Wed 13-07-16 00:50:12, Chen Gang wrote:
>= ; 
> 
> On 7/12/16 15:48, Michal&n= bsp;Hocko wrote:
> > On Tue 12-07-16 0= 3:47:42, Chen Gang wrote:
> > [...]
>= ; >> In our case, the 2 output s= ize are same, but under x86_64, the insns&n= bsp;are
> >> different. After uses bool,=  it uses push/pop instead of branch, for&nb= sp;me,
> >> it should be a little&n= bsp;better for catching.
> > 
> >=  The code generated for bool version looks&= nbsp;much worse. Look at the fast
> >&= nbsp;path. Gcc tries to reuse the retq from=  the fast path in the bool case
>&nb= sp;> and so it has to push rbp and&= nbsp;rbx on the stack.
> > 
> &= gt; That being said, gcc doesn't seem to&nb= sp;generate a better code for bool so
>&n= bsp;> I do not think this is really = ;worth it.
> >
> 
> The code&= nbsp;below also merge 3 statements into 1 r= eturn statement, although
> for me, it is=  a little more readable, it will generate&n= bsp;a little bad code.
> That is the = ;reason why the output looks a little bad.<= br >> 
> In our case, for gcc 6.0= , using bool instead of int for bool f= unction
> will get the same output under&= nbsp;x86_64.

If the output is same then = ;there is no reason to change it.

>&= nbsp;In our case, for gcc 4.8, using bool&n= bsp;instead of int for bool function
> wi= ll get a little better output under x86_64.=

I had a different impression and the&n= bsp;fast path code had more
instructions. But&nbs= p;anyway, is there really a strong reason t= o change
those return values in the first&nb= sp;place? Isn't that just a pointless code
c= hurn?
-- 
Michal Hocko
SUSE Labs
=
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