Date: Wed, 29 Aug 2012 01:04:12 +0000 (UTC) From: Jim Harris <jimharris@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org Subject: svn commit: r239798 - stable/9/sys/sys Message-ID: <201208290104.q7T14CcR057368@svn.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: jimharris Date: Wed Aug 29 01:04:12 2012 New Revision: 239798 URL: http://svn.freebsd.org/changeset/base/239798 Log: MFC r239591: Remove unncessary atomic operation when reading process flags in PMC_PROC_IS_USING_PMCS macro. Invocations of this macro are not synchronized with setting/clearing of P_HWPMC flag, so the atomic operation here isn't needed. Removing the atomic operation provides noticeable improvement (5-6%) on some scheduler-intensive workloads with HWPMC_HOOKS enabled on an 8C Sandy Bridge Xeon system. Sponsored by: Intel Modified: stable/9/sys/sys/pmckern.h Directory Properties: stable/9/sys/ (props changed) Modified: stable/9/sys/sys/pmckern.h ============================================================================== --- stable/9/sys/sys/pmckern.h Wed Aug 29 00:53:58 2012 (r239797) +++ stable/9/sys/sys/pmckern.h Wed Aug 29 01:04:12 2012 (r239798) @@ -201,8 +201,7 @@ do { \ /* Check if a process is using HWPMCs.*/ #define PMC_PROC_IS_USING_PMCS(p) \ - (__predict_false(atomic_load_acq_int(&(p)->p_flag) & \ - P_HWPMC)) + (__predict_false(p->p_flag & P_HWPMC)) /* Check if a thread have pending user capture. */ #define PMC_IS_PENDING_CALLCHAIN(p) \
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201208290104.q7T14CcR057368>