diff mbox series

[2/2] x86/mwait-idle: Customize IceLake server support

Message ID 1602558169-23140-2-git-send-email-igor.druzhinin@citrix.com (mailing list archive)
State Superseded
Headers show
Series [1/2] x86/intel: insert Ice Lake X (server) model numbers | expand

Commit Message

Igor Druzhinin Oct. 13, 2020, 3:02 a.m. UTC 
From: Chen Yu <yu.c.chen@intel.com>

On ICX platform, the C1E auto-promotion is enabled by default.
As a result, the CPU might fall into C1E more offen than previous
platforms. So disable C1E auto-promotion and expose C1E as a separate
idle state.

Beside C1 and C1E, the exit latency of C6 was measured
by a dedicated tool. However the exit latency(41us) exposed
by _CST is much smaller than the one we measured(128us). This
is probably due to the _CST uses the exit latency when woken
up from PC0+C6, rather than PC6+C6 when C6 was measured. Choose
the latter as we need the longest latency in theory.

Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
[Linux commit a472ad2bcea479ba068880125d7273fc95c14b70]
Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>
---
Applying this gives almost 100% boost in sysbench cpu test on Whitley SDP
---
 xen/arch/x86/cpu/mwait-idle.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

Comments

Jan Beulich Oct. 14, 2020, 4:09 p.m. UTC | #1 
On 13.10.2020 05:02, Igor Druzhinin wrote:
> From: Chen Yu <yu.c.chen@intel.com>
> 
> On ICX platform, the C1E auto-promotion is enabled by default.
> As a result, the CPU might fall into C1E more offen than previous
> platforms. So disable C1E auto-promotion and expose C1E as a separate
> idle state.
> 
> Beside C1 and C1E, the exit latency of C6 was measured
> by a dedicated tool. However the exit latency(41us) exposed
> by _CST is much smaller than the one we measured(128us). This
> is probably due to the _CST uses the exit latency when woken
> up from PC0+C6, rather than PC6+C6 when C6 was measured. Choose
> the latter as we need the longest latency in theory.
> 
> Signed-off-by: Chen Yu <yu.c.chen@intel.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> [Linux commit a472ad2bcea479ba068880125d7273fc95c14b70]
> Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>

Acked-by: Jan Beulich <jbeulich@suse.com>
diff mbox series

Patch

diff --git a/xen/arch/x86/cpu/mwait-idle.c b/xen/arch/x86/cpu/mwait-idle.c
index 8add13d..f0c6ff9 100644
--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -554,6 +554,28 @@  static const struct cpuidle_state skx_cstates[] = {
 	{}
 };
 
+static const struct cpuidle_state icx_cstates[] = {
+       {
+               .name = "C1-ICX",
+               .flags = MWAIT2flg(0x00),
+               .exit_latency = 1,
+               .target_residency = 1,
+       },
+       {
+               .name = "C1E-ICX",
+               .flags = MWAIT2flg(0x01),
+               .exit_latency = 4,
+               .target_residency = 4,
+       },
+       {
+               .name = "C6-ICX",
+               .flags = MWAIT2flg(0x20) | CPUIDLE_FLAG_TLB_FLUSHED,
+               .exit_latency = 128,
+               .target_residency = 384,
+       },
+       {}
+};
+
 static const struct cpuidle_state atom_cstates[] = {
 	{
 		.name = "C1E-ATM",
@@ -904,6 +926,11 @@  static const struct idle_cpu idle_cpu_skx = {
 	.disable_promotion_to_c1e = 1,
 };
 
+static const struct idle_cpu idle_cpu_icx = {
+       .state_table = icx_cstates,
+       .disable_promotion_to_c1e = 1,
+};
+
 static const struct idle_cpu idle_cpu_avn = {
 	.state_table = avn_cstates,
 	.disable_promotion_to_c1e = 1,
@@ -958,6 +985,7 @@  static const struct x86_cpu_id intel_idle_ids[] __initconstrel = {
 	ICPU(0x8e, skl),
 	ICPU(0x9e, skl),
 	ICPU(0x55, skx),
+	ICPU(0x6a, icx),
 	ICPU(0x57, knl),
 	ICPU(0x85, knl),
 	ICPU(0x5c, bxt),