linux-kernel - [PATCH] sched/x86: Calculate booted cores after construction of sibling

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Message-ID: <20120531073738.GH7511@linux.vnet.ibm.com>
Date:	Thu, 31 May 2012 13:07:38 +0530
From:	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...hat.com, peterz@...radead.org
Subject: [PATCH] sched/x86: Calculate booted cores after construction of
 sibling_mask

While booting tip (1d06e6d354) on qemu with -smp sockets=1,cores=2,threads=2
topology. There is a mismatch between the number of cores actually present
and cores reported.

Changes related to calculating the number of booted cores was introduced
by 316ad248307fb (sched/x86: Rewrite set_cpu_sibling_map()). With the
clean up, the calculation of booted cores per package is done on an
incompletely constructed sibling_mask per cpu.

sched/x86: Calculate booted cores after construction of sibling_mask

This patch re-introduces the old behaviour of constructing the complete
sibling mask of the cpu, before calculating the number of cores booted.

On qemu booted with -smp sockets=1,cores=2,threads=2,
Before:
$ cat /proc/cpuinfo |grep cores
cpu cores       : 2
cpu cores       : 1
cpu cores       : 4
cpu cores       : 3

With the patch:
$ cat /proc/cpuinfo |grep cores
cpu cores       : 2
cpu cores       : 2
cpu cores       : 2
cpu cores       : 2

Signed-off-by: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
---
 arch/x86/kernel/smpboot.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index fd019d7..a8d78f3 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -382,7 +382,12 @@ void __cpuinit set_cpu_sibling_map(int cpu)
 		if ((i == cpu) || (has_mc && match_llc(c, o)))
 			link_mask(llc_shared, cpu, i);

-		if ((i == cpu) || (has_mc && match_mc(c, o))) {
+	}
+
+	for_each_cpu(i, cpu_sibling_setup_mask) {
+		o = &cpu_data(i);
+
+	if ((i == cpu) || (has_mc && match_mc(c, o))) {
 			link_mask(core, cpu, i);

 			/*

--
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