diff mbox series

[v4,08/24] x86/resctrl: Allocate the cleanest CLOSID by searching closid_num_dirty_rmid

Message ID 20230525180209.19497-9-james.morse@arm.com
State New
Headers
Series x86/resctrl: monitored closid+rmid together, separate arch/fs locking |

Commit Message

James Morse May 25, 2023, 6:01 p.m. UTC 
  MPAM's PMG bits extend its PARTID space, meaning the same PMG value can be
used for different control groups.

This means once a CLOSID is allocated, all its monitoring ids may still be
dirty, and held in limbo.

Instead of allocating the first free CLOSID, on architectures where
CONFIG_RESCTRL_RMID_DEPENDS_ON_COSID is enabled, search
closid_num_dirty_rmid[] to find the cleanest CLOSID.

The CLOSID found is returned to closid_alloc() for the free list
to be updated.

Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/x86/kernel/cpu/resctrl/internal.h |  2 ++
 arch/x86/kernel/cpu/resctrl/monitor.c  | 45 ++++++++++++++++++++++++++
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 19 ++++++++---
 3 files changed, 61 insertions(+), 5 deletions(-)

Comments

Reinette Chatre June 15, 2023, 10:09 p.m. UTC | #1 
Hi James,

On 5/25/2023 11:01 AM, James Morse wrote:

...

> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 1e7fa40ee471..128d4c7206e4 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -379,6 +379,51 @@ static struct rmid_entry *resctrl_find_free_rmid(u32 closid)
>  	return ERR_PTR(-ENOSPC);
>  }
>  
> +/**
> + * resctrl_find_cleanest_closid() - Find a CLOSID where all the associated
> + *                                  RMID are clean, or the CLOSID that has
> + *                                  the most clean RMID.
> + *
> + * MPAM's equivalent of RMID are per-CLOSID, meaning a freshly allocated CLOSID
> + * may not be able to allocate clean RMID. To avoid this the allocator will
> + * choose the CLOSID with the most clean RMID.
> + *
> + * When the CLOSID and RMID are independent numbers, the first free CLOSID will
> + * be returned.
> + *
> + * Call when CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID is defined. If not, call
> + * resctrl_closid_alloc_first_free() instead.

I was not able to find where resctrl_closid_alloc_first_free() is introduced.

> + */
> +int resctrl_find_cleanest_closid(void)
> +{
> +	u32 cleanest_closid = ~0, iter_num_dirty;
> +	int i = 0;
> +
> +	lockdep_assert_held(&rdtgroup_mutex);
> +
> +	if (!IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID))
> +		return -EIO;
> +
> +	for (i = 0; i < closids_supported(); i++) {
> +		if (closid_allocated(i))
> +			continue;
> +
> +		iter_num_dirty = closid_num_dirty_rmid[i];
> +		if (iter_num_dirty == 0)
> +			return i;
> +
> +		if (cleanest_closid == ~0)
> +			cleanest_closid = i;
> +
> +		if (iter_num_dirty < closid_num_dirty_rmid[cleanest_closid])
> +			cleanest_closid = i;
> +	}
> +

Reinette
James Morse July 28, 2023, 4:35 p.m. UTC | #2 
Hi Reinette,

On 6/15/23 23:09, Reinette Chatre wrote:
> On 5/25/2023 11:01 AM, James Morse wrote:
>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
>> index 1e7fa40ee471..128d4c7206e4 100644
>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>> @@ -379,6 +379,51 @@ static struct rmid_entry *resctrl_find_free_rmid(u32 closid)
>>   	return ERR_PTR(-ENOSPC);
>>   }
>>   
>> +/**
>> + * resctrl_find_cleanest_closid() - Find a CLOSID where all the associated
>> + *                                  RMID are clean, or the CLOSID that has
>> + *                                  the most clean RMID.
>> + *
>> + * MPAM's equivalent of RMID are per-CLOSID, meaning a freshly allocated CLOSID
>> + * may not be able to allocate clean RMID. To avoid this the allocator will
>> + * choose the CLOSID with the most clean RMID.
>> + *
>> + * When the CLOSID and RMID are independent numbers, the first free CLOSID will
>> + * be returned.
>> + *
>> + * Call when CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID is defined. If not, call
>> + * resctrl_closid_alloc_first_free() instead.
> 
> I was not able to find where resctrl_closid_alloc_first_free() is introduced.

Oops, this was the name for the other half of closid_alloc() back when I thought it was more
readable to give it a name. The version posted leaves it alone to reduce the churn. I'll drop this paragraph.


Thanks,

James
diff mbox series

Patch

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 23e20f89d2b3..96fb7658ff74 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -557,5 +557,7 @@  void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
 void __init thread_throttle_mode_init(void);
 void __init mbm_config_rftype_init(const char *config);
 void rdt_staged_configs_clear(void);
+bool closid_allocated(unsigned int closid);
+int resctrl_find_cleanest_closid(void);
 
 #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 1e7fa40ee471..128d4c7206e4 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -379,6 +379,51 @@  static struct rmid_entry *resctrl_find_free_rmid(u32 closid)
 	return ERR_PTR(-ENOSPC);
 }
 
+/**
+ * resctrl_find_cleanest_closid() - Find a CLOSID where all the associated
+ *                                  RMID are clean, or the CLOSID that has
+ *                                  the most clean RMID.
+ *
+ * MPAM's equivalent of RMID are per-CLOSID, meaning a freshly allocated CLOSID
+ * may not be able to allocate clean RMID. To avoid this the allocator will
+ * choose the CLOSID with the most clean RMID.
+ *
+ * When the CLOSID and RMID are independent numbers, the first free CLOSID will
+ * be returned.
+ *
+ * Call when CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID is defined. If not, call
+ * resctrl_closid_alloc_first_free() instead.
+ */
+int resctrl_find_cleanest_closid(void)
+{
+	u32 cleanest_closid = ~0, iter_num_dirty;
+	int i = 0;
+
+	lockdep_assert_held(&rdtgroup_mutex);
+
+	if (!IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID))
+		return -EIO;
+
+	for (i = 0; i < closids_supported(); i++) {
+		if (closid_allocated(i))
+			continue;
+
+		iter_num_dirty = closid_num_dirty_rmid[i];
+		if (iter_num_dirty == 0)
+			return i;
+
+		if (cleanest_closid == ~0)
+			cleanest_closid = i;
+
+		if (iter_num_dirty < closid_num_dirty_rmid[cleanest_closid])
+			cleanest_closid = i;
+	}
+
+	if (cleanest_closid == ~0)
+		return -ENOSPC;
+	return cleanest_closid;
+}
+
 /*
  * For MPAM the RMID value is not unique, and has to be considered with
  * the CLOSID. The (CLOSID, RMID) pair is allocated on all domains, which
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 6bf5623f82b4..1120c7700126 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -132,11 +132,20 @@  static void closid_init(void)
 
 static int closid_alloc(void)
 {
-	u32 closid = ffs(closid_free_map);
+	u32 closid;
+	int err;
 
-	if (closid == 0)
-		return -ENOSPC;
-	closid--;
+	if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID)) {
+		err = resctrl_find_cleanest_closid();
+		if (err < 0)
+			return err;
+		closid = err;
+	} else {
+		closid = ffs(closid_free_map);
+		if (closid == 0)
+			return -ENOSPC;
+		closid--;
+	}
 	clear_bit(closid, &closid_free_map);
 
 	return closid;
@@ -154,7 +163,7 @@  void closid_free(int closid)
  * Return: true if @closid is currently associated with a resource group,
  * false if @closid is free
  */
-static bool closid_allocated(unsigned int closid)
+bool closid_allocated(unsigned int closid)
 {
 	return !test_bit(closid, &closid_free_map);
 }