From: Yinghai Lu <yinghai@kernel.org>
To: Suresh Siddha <suresh.b.siddha@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"ananth@in.ibm.com" <ananth@in.ibm.com>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, Yinghai Lu <yinghai@kernel.org>
Subject:
Date: Mon, 11 Jan 2010 18:45:58 -0800 [thread overview]
Message-ID: <1263264358-3896-4-git-send-email-yinghai@kernel.org> (raw)
In-Reply-To: <1263264358-3896-1-git-send-email-yinghai@kernel.org>
some systems that have disable cpus entries because same
BIOS will support 2 sockets and 4 sockets and more at
same time, BIOS just leave some disable entries, but
those system do not support cpu hotplug. we don't need
treat disabled_cpus as hotplug cpus.
so we can make nr_cpu_ids smaller and save more space
(pcpu data allocations), and could make some systems run
with logical flat instead of physical flat apic mode
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
---
arch/x86/kernel/smpboot.c | 39 +++++++++++++++++++++++++++++++++++++--
1 file changed, 37 insertions(+), 2 deletions(-)
Index: linux-2.6/arch/x86/kernel/smpboot.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/smpboot.c
+++ linux-2.6/arch/x86/kernel/smpboot.c
@@ -47,6 +47,7 @@
#include <linux/bootmem.h>
#include <linux/err.h>
#include <linux/nmi.h>
+#include <linux/dmi.h>
#include <linux/tboot.h>
#include <asm/acpi.h>
@@ -1180,6 +1181,24 @@ static int __init _setup_possible_cpus(c
}
early_param("possible_cpus", _setup_possible_cpus);
+static __initdata int treat_disabled_cpus_as_hotplug;
+static __init int hotplug_cpus_check(const struct dmi_system_id *d)
+{
+ printk(KERN_NOTICE "%s detected: treat disabled cpus as hotplug ones\n", d->ident);
+ treat_disabled_cpus_as_hotplug = 1;
+
+ return 0;
+}
+
+static struct dmi_system_id hotplug_cpus_dmi_table[] __initdata = {
+ { hotplug_cpus_check, "WHICH VENDOR WHAT SYSTEM",
+ { DMI_MATCH(DMI_BIOS_VENDOR, "WHAT VENDOR"),
+ DMI_MATCH(DMI_BIOS_VERSION, "WHAT VER"),
+ }
+ },
+ { } /* NULL entry stops DMI scanning */
+};
+
/*
* cpu_possible_mask should be static, it cannot change as cpu's
@@ -1206,8 +1225,24 @@ __init void prefill_possible_map(void)
if (!num_processors)
num_processors = 1;
- if (setup_possible_cpus == -1)
- possible = num_processors + disabled_cpus;
+ if (setup_possible_cpus == -1) {
+ possible = num_processors;
+ /*
+ * do we have better way to detect hotplug cpus?
+ *
+ * some systems that have disable cpus entries because same
+ * BIOS will support 2 sockets and 4 sockets and more at
+ * same time, BIOS just leave some disable entries, but
+ * those system do not support cpu hotplug. we don't need
+ * treat disabled_cpus as hotplug cpus.
+ * so we can make nr_cpu_ids smaller and save more space
+ * (pcpu data allocations), and could make some systems run
+ * with logical flat instead of physical flat apic mode
+ */
+ dmi_check_system(hotplug_cpus_dmi_table);
+ if (treat_disabled_cpus_as_hotplug)
+ possible += disabled_cpus;
+ }
else
possible = setup_possible_cpus;
prev parent reply other threads:[~2010-01-12 2:47 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-12 2:45 Yinghai Lu
2010-01-12 2:45 ` Yinghai Lu
2010-01-12 2:45 ` Yinghai Lu
2010-01-12 2:45 ` Yinghai Lu [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1263264358-3896-4-git-send-email-yinghai@kernel.org \
--to=yinghai@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=ananth@in.ibm.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=suresh.b.siddha@intel.com \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).