From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 1218A6B0346 for ; Wed, 7 Feb 2018 12:12:19 -0500 (EST) Received: by mail-wr0-f199.google.com with SMTP id i12so864291wra.22 for ; Wed, 07 Feb 2018 09:12:19 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id v15sor1542903edl.9.2018.02.07.09.12.17 for (Google Transport Security); Wed, 07 Feb 2018 09:12:17 -0800 (PST) Date: Wed, 7 Feb 2018 20:12:15 +0300 From: "Kirill A. Shutemov" Subject: Re: [RFC 0/3] x86: Patchable constants Message-ID: <20180207171215.b52hql2bv5wzff6o@node.shutemov.name> References: <20180207145913.2703-1-kirill.shutemov@linux.intel.com> <20180207162507.GB25219@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180207162507.GB25219@hirez.programming.kicks-ass.net> Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: "Kirill A. Shutemov" , Linus Torvalds , x86@kernel.org, Tom Lendacky , Dave Hansen , Andy Lutomirski , Borislav Petkov , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Wed, Feb 07, 2018 at 05:25:07PM +0100, Peter Zijlstra wrote: > On Wed, Feb 07, 2018 at 05:59:10PM +0300, Kirill A. Shutemov wrote: > > This conversion makes GCC generate worse code. Conversion __PHYSICAL_MASK > > to a patchable constant adds about 5k in .text on defconfig and makes it > > slightly slower at runtime (~0.2% on my box). > > Do you have explicit examples for the worse code? That might give clue > on how to improve things. Clarification: increase by 5k was for defconfig, where I replaced pure constant define __PHYSICAL_MASK with patchable constant. With CONFIG_AMD_MEM_ENCRYPT=y increase is smaller: ~1.8k. The disassembler below is for CONFIG_AMD_MEM_ENCRYPT=y. Before: Dump of assembler code for function migration_entry_wait: 0xffffffff8118ab40 <+0>: mov (%rsi),%rcx 0xffffffff8118ab43 <+3>: shr $0x9,%rdx 0xffffffff8118ab47 <+7>: mov 0x10aecba(%rip),%r8 # 0xffffffff82239808 0xffffffff8118ab4e <+14>: mov %rdx,%rax 0xffffffff8118ab51 <+17>: mov 0x10aec90(%rip),%r9 # 0xffffffff822397e8 0xffffffff8118ab58 <+24>: movabs $0x3fffffe00000,%rsi 0xffffffff8118ab62 <+34>: and $0xff8,%eax 0xffffffff8118ab67 <+39>: test $0x80,%cl 0xffffffff8118ab6a <+42>: not %r8 0xffffffff8118ab6d <+45>: jne 0xffffffff8118ab79 0xffffffff8118ab6f <+47>: movabs $0x3ffffffff000,%rsi 0xffffffff8118ab79 <+57>: and %r8,%rsi 0xffffffff8118ab7c <+60>: add 0x10aec75(%rip),%rax # 0xffffffff822397f8 0xffffffff8118ab83 <+67>: and %rsi,%rcx 0xffffffff8118ab86 <+70>: mov %rcx,%rdx 0xffffffff8118ab89 <+73>: shr $0x6,%rdx 0xffffffff8118ab8d <+77>: mov %rax,%rsi 0xffffffff8118ab90 <+80>: lea 0x30(%r9,%rdx,1),%rdx 0xffffffff8118ab95 <+85>: add %rcx,%rsi 0xffffffff8118ab98 <+88>: jmpq 0xffffffff8118aa20 <__migration_entry_wait> After: Dump of assembler code for function migration_entry_wait: 0xffffffff8118b3e0 <+0>: mov (%rsi),%rsi 0xffffffff8118b3e3 <+3>: mov %rdx,%rax 0xffffffff8118b3e6 <+6>: mov 0x10ae41b(%rip),%r8 # 0xffffffff82239808 0xffffffff8118b3ed <+13>: shr $0x9,%rax 0xffffffff8118b3f1 <+17>: and $0xff8,%eax 0xffffffff8118b3f6 <+22>: test $0x80,%sil 0xffffffff8118b3fa <+26>: jne 0xffffffff8118b432 0xffffffff8118b3fc <+28>: mov %rsi,%rdx 0xffffffff8118b3ff <+31>: movabs $0x3fffffffffff,%rcx 0xffffffff8118b409 <+41>: and %rcx,%rdx 0xffffffff8118b40c <+44>: and $0xfffffffffffff000,%rcx 0xffffffff8118b413 <+51>: shr $0xc,%rdx 0xffffffff8118b417 <+55>: shl $0x6,%rdx 0xffffffff8118b41b <+59>: lea 0x30(%r8,%rdx,1),%rdx 0xffffffff8118b420 <+64>: add 0x10ae3f1(%rip),%rax # 0xffffffff82239818 0xffffffff8118b427 <+71>: and %rcx,%rsi 0xffffffff8118b42a <+74>: add %rax,%rsi 0xffffffff8118b42d <+77>: jmpq 0xffffffff8118b2c0 <__migration_entry_wait> 0xffffffff8118b432 <+82>: mov %rsi,%rdx 0xffffffff8118b435 <+85>: and $0xffffffffffe00000,%rdx 0xffffffff8118b43c <+92>: movabs $0x3fffffffffff,%rcx 0xffffffff8118b446 <+102>: and %rcx,%rdx 0xffffffff8118b449 <+105>: and $0xffffffffffe00000,%rcx 0xffffffff8118b450 <+112>: shr $0x6,%rdx 0xffffffff8118b454 <+116>: lea 0x30(%r8,%rdx,1),%rdx 0xffffffff8118b459 <+121>: jmp 0xffffffff8118b420 -- Kirill A. Shutemov -- 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