Date: Sun, 27 Aug 2017 05:14:48 +0000 (UTC) From: Conrad Meyer <cem@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r322942 - head/sys/kern Message-ID: <201708270514.v7R5EmDK064785@repo.freebsd.org>
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Author: cem Date: Sun Aug 27 05:14:48 2017 New Revision: 322942 URL: https://svnweb.freebsd.org/changeset/base/322942 Log: Improve scheduler performance Improve scheduler performance by flattening nonsensical topology layers (layers with only one child don't serve any purpose). This is especially relevant on non-AMD Zen systems after r322776. On my dual core Intel laptop, this brings the kern.sched.topology_spec table down from three levels to two. Submitted by: jeff Reviewed by: attilio Sponsored by: Dell EMC Isilon Modified: head/sys/kern/subr_smp.c Modified: head/sys/kern/subr_smp.c ============================================================================== --- head/sys/kern/subr_smp.c Sun Aug 27 03:10:16 2017 (r322941) +++ head/sys/kern/subr_smp.c Sun Aug 27 05:14:48 2017 (r322942) @@ -630,6 +630,15 @@ smp_topo(void) panic("Built bad topology at %p. CPU mask (%s) != (%s)", top, cpusetobj_strprint(cpusetbuf, &top->cg_mask), cpusetobj_strprint(cpusetbuf2, &all_cpus)); + + /* + * Collapse nonsense levels that may be created out of convenience by + * the MD layers. They cause extra work in the search functions. + */ + while (top->cg_children == 1) { + top = &top->cg_child[0]; + top->cg_parent = NULL; + } return (top); }
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