diff options
| author | Len Brown <[email protected]> | 2015-08-16 11:45:47 -0400 |
|---|---|---|
| committer | Ingo Molnar <[email protected]> | 2015-08-17 10:42:27 +0200 |
| commit | a9bcaa02a5104ace6a9d9e4a9cd9192a9e7744d6 (patch) | |
| tree | 6ef02ae00a81bf4afe1df91defc2ad6b1665a122 | |
| parent | 2d99af8e8fd6c2dea11ab539f7aba69c37b845b4 (diff) | |
x86/smpboot: Remove SIPI delays from cpu_up()
MPS 1.4 example code shows the following required delays during processor
on-lining:
INIT
udelay(10,000)
SIPI
udelay(200)
SIPI
udelay(200) /* Linux actually implements this as udelay(300) */
Linux skips the udelay(10,000) on modern processors.
This patch removes the udelay(200) after each SIPI
on those same processors.
All three legacy delays can be restored by the cmdline
"cpu_init_udelay=10000".
As measured by analyze_suspend.py, this patch speeds
processor resume time on my desktop from 2.4ms to 1.8ms, per AP.
Signed-off-by: Len Brown <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Igor Mammedov <[email protected]>
Cc: Jan H. Schönherr <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Zhu Guihua <[email protected]>
Link: http://lkml.kernel.org/r/a5dfdbc8fbfdd813784da204aad5677fe459ac37.1439739165.git.len.brown@intel.com
Signed-off-by: Ingo Molnar <[email protected]>
| -rw-r--r-- | arch/x86/kernel/smpboot.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 310b6f0bf6f7..674026455fee 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -665,7 +665,8 @@ wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip) /* * Give the other CPU some time to accept the IPI. */ - udelay(300); + if (init_udelay) + udelay(300); pr_debug("Startup point 1\n"); @@ -675,7 +676,8 @@ wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip) /* * Give the other CPU some time to accept the IPI. */ - udelay(200); + if (init_udelay) + udelay(200); if (maxlvt > 3) /* Due to the Pentium erratum 3AP. */ apic_write(APIC_ESR, 0); |