From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp02.au.ibm.com (e23smtp02.au.ibm.com [202.81.31.144]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 5C09A1A0271 for ; Tue, 24 Mar 2015 15:27:44 +1100 (AEDT) Received: from /spool/local by e23smtp02.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 24 Mar 2015 14:27:42 +1000 Received: from d23relay08.au.ibm.com (d23relay08.au.ibm.com [9.185.71.33]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id 6D34E2BB0040 for ; Tue, 24 Mar 2015 15:27:38 +1100 (EST) Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay08.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t2O4RTD538076524 for ; Tue, 24 Mar 2015 15:27:38 +1100 Received: from d23av01.au.ibm.com (localhost [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t2O4R31a001773 for ; Tue, 24 Mar 2015 15:27:04 +1100 Message-ID: <5510E77F.1020903@linux.vnet.ibm.com> Date: Tue, 24 Mar 2015 09:56:39 +0530 From: Anshuman Khandual MIME-Version: 1.0 To: Michael Ellerman Subject: Re: [PATCH 1/3] powerpc/tm: Abort syscalls in active transactions References: <6ebcb9f982f7cb100aef954cd7dc6a6081cd9134.1426740212.git.sam.bobroff@au1.ibm.com> <550BE2AB.2050604@linux.vnet.ibm.com> <1427162659.28572.3.camel@ellerman.id.au> In-Reply-To: <1427162659.28572.3.camel@ellerman.id.au> Content-Type: text/plain; charset=UTF-8 Cc: mikey@neuling.org, azanella@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, Sam Bobroff , matt@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 03/24/2015 07:34 AM, Michael Ellerman wrote: > On Fri, 2015-03-20 at 14:34 +0530, Anshuman Khandual wrote: >> On 03/19/2015 10:13 AM, Sam Bobroff wrote: >>> This patch changes the syscall handler to doom (tabort) active >>> transactions when a syscall is made and return immediately without >>> performing the syscall. >>> >>> Currently, the system call instruction automatically suspends an >>> active transaction which causes side effects to persist when an active >>> transaction fails. >>> >>> This does change the kernel's behaviour, but in a way that was >>> documented as unsupported. It doesn't reduce functionality because >>> syscalls will still be performed after tsuspend. It also provides a >>> consistent interface and makes the behaviour of user code >>> substantially the same across powerpc and platforms that do not >>> support suspended transactions (e.g. x86 and s390). >>> >>> Performance measurements using >>> http://ozlabs.org/~anton/junkcode/null_syscall.c >>> indicate the cost of a system call increases by about 0.5%. >> >> Performance test results verified which shows an improvement of >> around ~0.52% with the patch compared to without it. >> >> [With patch] null_syscall: 757.59 cycles 100.00% >> [Without patch]] null_syscall: 753.66 cycles 100.00% > > No that's a performance *decrease* with the patch applied. ? Micheal, thats true. The cycle counts are more with patch being applied. Here are some more results on mainline. Without the patch: null_syscall: 754.14 cycles 100.00% null_syscall: 754.50 cycles 100.00% null_syscall: 754.17 cycles 100.00% null_syscall: 754.43 cycles 100.00% null_syscall: 754.17 cycles 100.00% null_syscall: 754.20 cycles 100.00% null_syscall: 754.47 cycles 100.00% null_syscall: 754.70 cycles 100.00% null_syscall: 754.43 cycles 100.00% null_syscall: 753.72 cycles 100.00% With the patch: null_syscall: 756.76 cycles 100.00% null_syscall: 756.40 cycles 100.00% null_syscall: 756.46 cycles 100.00% null_syscall: 756.86 cycles 100.00% null_syscall: 756.56 cycles 100.00% null_syscall: 756.66 cycles 100.00% null_syscall: 756.86 cycles 100.00% null_syscall: 756.86 cycles 100.00% null_syscall: 757.02 cycles 100.00% null_syscall: 756.93 cycles 100.00%