Hi Babu,
On 8/6/24 3:00 PM, Babu Moger wrote:
Hardware provides a set of counters when mbm_cntr_assignable feature is
supported. These counters are used for assigning the events in resctrl
group when the feature is enabled.
"in resctrl group" -> "in a resctrl group"?
Introduce mbm_cntrs_free_map bitmap to track available and free counters
What is the difference between an available and a free counter?
and set of routines to allocate and free the counters.
Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
---
arch/x86/kernel/cpu/resctrl/internal.h | 2 ++
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 33 ++++++++++++++++++++++++++
2 files changed, 35 insertions(+)
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 154983a67646..6263362496a3 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -662,6 +662,8 @@ void __check_limbo(struct rdt_mon_domain *d, bool force_free);
void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
void __init resctrl_file_fflags_init(const char *config,
unsigned long fflags);
+int mbm_cntr_alloc(struct rdt_resource *r);
+void mbm_cntr_free(u32 cntr_id);
void rdt_staged_configs_clear(void);
bool closid_allocated(unsigned int closid);
int resctrl_find_cleanest_closid(void);
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index ab4fab3b7cf1..c818965e36c9 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -185,6 +185,37 @@ bool closid_allocated(unsigned int closid)
return !test_bit(closid, &closid_free_map);
}
+/*
+ * Counter bitmap for tracking the available counters.
+ * ABMC feature provides set of hardware counters for enabling events.
"ABMC feature" -> "mbm_cntr_assign mode"
+ * Each event takes one hardware counter. Kernel needs to keep track
"Each event takes one hardware counter" -> "Each RMID and event pair takes
one hardware counter" ?
+ * of number of available counters.
"of number of available counters" -> "of the number of available counters"?
+ */
+static DECLARE_BITMAP(mbm_cntrs_free_map, 64);
+
+static void mbm_cntrs_init(struct rdt_resource *r)
+{
+ bitmap_fill(mbm_cntrs_free_map, r->mon.num_mbm_cntrs);
Apart from what James mentioned about the different sizes, please also
add checking that the resource actually supports monitoring and
assignable counters before proceeding with the bitmap ops.
+}
+
+int mbm_cntr_alloc(struct rdt_resource *r)
+{
+ int cntr_id;
+
+ cntr_id = find_first_bit(mbm_cntrs_free_map, r->mon.num_mbm_cntrs);
+ if (cntr_id >= r->mon.num_mbm_cntrs)
+ return -ENOSPC;
+
+ __clear_bit(cntr_id, mbm_cntrs_free_map);
+
+ return cntr_id;
+}
+
+void mbm_cntr_free(u32 cntr_id)
+{
+ __set_bit(cntr_id, mbm_cntrs_free_map);
+}
+
/**
* rdtgroup_mode_by_closid - Return mode of resource group with closid
* @closid: closid if the resource group
@@ -2748,6 +2779,8 @@ static int rdt_get_tree(struct fs_context *fc)
closid_init();
+ mbm_cntrs_init(&rdt_resources_all[RDT_RESOURCE_L3].r_resctrl);
+
if (resctrl_arch_mon_capable())
flags |= RFTYPE_MON;
This is also an example of what James mentioned elsewhere where there is an
assumption that this feature applies to the L3 resource. This has a consequence
that some code is global (like mbm_cntrs_free_map), assuming the L3 resource, while
other code takes the resource as parameter (eg. mbm_cntr_alloc()). This results
in inconsistent interface where, for example, allocating a counter needs resource
as parameter but freeing a counter does not. James already proposed different
treatment of the bitmap and L3 resource parameters, I expect with such guidance
the interfaces will become more intuitive.
Reinette
