From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 152E86B0253 for ; Mon, 11 Jul 2016 15:41:42 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id 63so137862000pfx.3 for ; Mon, 11 Jul 2016 12:41:42 -0700 (PDT) Received: from out4441.biz.mail.alibaba.com (out4441.biz.mail.alibaba.com. [47.88.44.41]) by mx.google.com with ESMTP id k29si1022009pfk.57.2016.07.11.12.41.40 for ; Mon, 11 Jul 2016 12:41:41 -0700 (PDT) Message-ID: <5783F7DE.9020203@emindsoft.com.cn> Date: Tue, 12 Jul 2016 03:47:42 +0800 From: Chen Gang MIME-Version: 1.0 Subject: Re: [PATCH] mm: migrate: Use bool instead of int for the return value of PageMovable References: <1468079704-5477-1-git-send-email-chengang@emindsoft.com.cn> <20160711002605.GD31817@bbox> In-Reply-To: <20160711002605.GD31817@bbox> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: akpm@linux-foundation.org, vbabka@suse.cz, mgorman@techsingularity.net, mhocko@suse.com, gi-oh.kim@profitbricks.com, iamjoonsoo.kim@lge.com, hillf.zj@alibaba-inc.com, rientjes@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chen Gang On 7/11/16 08:26, Minchan Kim wrote: > On Sat, Jul 09, 2016 at 11:55:04PM +0800, chengang@emindsoft.com.cn wrote: >> From: Chen Gang >> >> For pure bool function's return value, bool is a little better more or >> less than int. >> >> And return boolean result directly, since 'if' statement is also for >> boolean checking, and return boolean result, too. > > I just wanted to consistent with other PageXXX flags functions, PageAnon, > PageMappingFlags which returns int rather than bool. Although I agree bool > is natural, I want to be consistent with others rather than breaking at > the moment. > > Maybe if you feel it's really helpful, you might be able to handle all > of places I mentioned for better readability and keeping consistency. OK, I guess, we can send another patch for include/linux/page-flags.h for PageXXX. > But I doubt it's worth. > In our case, the 2 output size are same, but under x86_64, the insns are different. After uses bool, it uses push/pop instead of branch, for me, it should be a little better for catching. The orig: 0000000000001290 : 1290: 48 8b 47 08 mov 0x8(%rdi),%rax 1294: 83 e0 03 and $0x3,%eax 1297: 48 83 f8 02 cmp $0x2,%rax 129b: 74 03 je 12a0 <__SetPageMovable+0x12a0> 129d: 31 c0 xor %eax,%eax 129f: c3 retq 12a0: 55 push %rbp 12a1: 48 89 e5 mov %rsp,%rbp 12a4: e8 00 00 00 00 callq 12a9 <__SetPageMovable+0x12a9> 12a9: 48 85 c0 test %rax,%rax 12ac: 74 17 je 12c5 <__SetPageMovable+0x12c5> 12ae: 48 8b 50 68 mov 0x68(%rax),%rdx 12b2: 48 85 d2 test %rdx,%rdx 12b5: 74 0e je 12c5 <__SetPageMovable+0x12c5> 12b7: 48 83 7a 68 00 cmpq $0x0,0x68(%rdx) 12bc: b8 01 00 00 00 mov $0x1,%eax 12c1: 74 02 je 12c5 <__SetPageMovable+0x12c5> 12c3: 5d pop %rbp 12c4: c3 retq 12c5: 31 c0 xor %eax,%eax 12c7: 5d pop %rbp 12c8: c3 retq 12c9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) The new: 0000000000001290 : 1290: 48 8b 47 08 mov 0x8(%rdi),%rax 1294: 55 push %rbp 1295: 48 89 e5 mov %rsp,%rbp 1298: 53 push %rbx 1299: 31 db xor %ebx,%ebx 129b: 83 e0 03 and $0x3,%eax 129e: 48 83 f8 02 cmp $0x2,%rax 12a2: 74 05 je 12a9 <__SetPageMovable+0x12a9> 12a4: 89 d8 mov %ebx,%eax 12a6: 5b pop %rbx 12a7: 5d pop %rbp 12a8: c3 retq 12a9: e8 00 00 00 00 callq 12ae <__SetPageMovable+0x12ae> 12ae: 48 85 c0 test %rax,%rax 12b1: 74 f1 je 12a4 <__SetPageMovable+0x12a4> 12b3: 48 8b 40 68 mov 0x68(%rax),%rax 12b7: 48 85 c0 test %rax,%rax 12ba: 74 e8 je 12a4 <__SetPageMovable+0x12a4> 12bc: 48 83 78 68 00 cmpq $0x0,0x68(%rax) 12c1: 0f 95 c3 setne %bl 12c4: 89 d8 mov %ebx,%eax 12c6: 5b pop %rbx 12c7: 5d pop %rbp 12c8: c3 retq 12c9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) Thanks. -- Chen Gang (e??a??) Managing Natural Environments is the Duty of Human Beings. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org