[PATCH v6 21/21] x86/resctrl: Make resctrl_arch_rmid_read() return values in bytes

James Morse
2022-09-02T15:58:23Z

resctrl_arch_rmid_read() returns a value in chunks, as read from the
hardware. This needs scaling to bytes by mon_scale, as provided by
the architecture code.

Now that resctrl_arch_rmid_read() performs the overflow and corrections
itself, it may as well return a value in bytes directly. This allows
the accesses to the architecture specific 'hw' structure to be removed.

Move the mon_scale conversion into resctrl_arch_rmid_read().
mbm_bw_count() is updated to calculate bandwidth from bytes.

Reviewed-by: Jamie Iles <quic_jiles@quicinc.com>
Tested-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Cristian Marussi <cristian.marussi@arm.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
Changes since v3:
* Only set val in one place in restrl_arch_rmid_read()
* Use SZ_1M to improve readability
---
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 6 ++----
arch/x86/kernel/cpu/resctrl/internal.h | 4 ++--
arch/x86/kernel/cpu/resctrl/monitor.c | 24 +++++++++++------------
include/linux/resctrl.h | 2 +-
4 files changed, 16 insertions(+), 20 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index d3f7eb2ac14b..03fc91d8bc9f 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -549,7 +549,6 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
int rdtgroup_mondata_show(struct seq_file *m, void *arg)
{
struct kernfs_open_file *of = m->private;
- struct rdt_hw_resource *hw_res;
u32 resid, evtid, domid;
struct rdtgroup *rdtgrp;
struct rdt_resource *r;
@@ -569,8 +568,7 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
domid = md.u.domid;
evtid = md.u.evtid;

- hw_res = &rdt_resources_all[resid];
- r = &hw_res->r_resctrl;
+ r = &rdt_resources_all[resid].r_resctrl;
d = rdt_find_domain(r, domid, NULL);
if (IS_ERR_OR_NULL(d)) {
ret = -ENOENT;
@@ -584,7 +582,7 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
else if (rr.err == -EINVAL)
seq_puts(m, "Unavailable\n");
else
- seq_printf(m, "%llu\n", rr.val * hw_res->mon_scale);
+ seq_printf(m, "%llu\n", rr.val);

out:
rdtgroup_kn_unlock(of->kn);
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index c05e9b7cf77a..5f7128686cfd 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -279,13 +279,13 @@ struct rftype {

/**
* struct mbm_state - status for each MBM counter in each domain
- * @prev_bw_chunks: Previous chunks value read for bandwidth calculation
+ * @prev_bw_bytes: Previous bytes value read for bandwidth calculation
* @prev_bw: The most recent bandwidth in MBps
* @delta_bw: Difference between the current and previous bandwidth
* @delta_comp: Indicates whether to compute the delta_bw
*/
struct mbm_state {
- u64 prev_bw_chunks;
+ u64 prev_bw_bytes;
u32 prev_bw;
u32 delta_bw;
bool delta_comp;
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 8d15568d7121..efe0c30d3a12 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -16,6 +16,7 @@
*/

#include <linux/module.h>
+#include <linux/sizes.h>
#include <linux/slab.h>

#include <asm/cpu_device_id.h>
@@ -189,7 +190,7 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
struct arch_mbm_state *am;
- u64 msr_val;
+ u64 msr_val, chunks;

if (!cpumask_test_cpu(smp_processor_id(), &d->cpu_mask))
return -EINVAL;
@@ -214,12 +215,14 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
if (am) {
am->chunks += mbm_overflow_count(am->prev_msr, msr_val,
hw_res->mbm_width);
- *val = get_corrected_mbm_count(rmid, am->chunks);
+ chunks = get_corrected_mbm_count(rmid, am->chunks);
am->prev_msr = msr_val;
} else {
- *val = msr_val;
+ chunks = msr_val;
}

+ *val = chunks * hw_res->mon_scale;
+
return 0;
}

@@ -232,7 +235,6 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
void __check_limbo(struct rdt_domain *d, bool force_free)
{
struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
- struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
struct rmid_entry *entry;
u32 crmid = 1, nrmid;
bool rmid_dirty;
@@ -255,7 +257,6 @@ void __check_limbo(struct rdt_domain *d, bool force_free)
QOS_L3_OCCUP_EVENT_ID, &val)) {
rmid_dirty = true;
} else {
- val *= hw_res->mon_scale;
rmid_dirty = (val >= resctrl_rmid_realloc_threshold);
}

@@ -299,7 +300,6 @@ int alloc_rmid(void)
static void add_rmid_to_limbo(struct rmid_entry *entry)
{
struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
- struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
struct rdt_domain *d;
int cpu, err;
u64 val = 0;
@@ -311,7 +311,6 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
err = resctrl_arch_rmid_read(r, d, entry->rmid,
QOS_L3_OCCUP_EVENT_ID,
&val);
- val *= hw_res->mon_scale;
if (err || val <= resctrl_rmid_realloc_threshold)
continue;
}
@@ -403,15 +402,14 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr)
*/
static void mbm_bw_count(u32 rmid, struct rmid_read *rr)
{
- struct rdt_hw_resource *hw_res = resctrl_to_arch_res(rr->r);
struct mbm_state *m = &rr->d->mbm_local[rmid];
- u64 cur_bw, chunks, cur_chunks;
+ u64 cur_bw, bytes, cur_bytes;

- cur_chunks = rr->val;
- chunks = cur_chunks - m->prev_bw_chunks;
- m->prev_bw_chunks = cur_chunks;
+ cur_bytes = rr->val;
+ bytes = cur_bytes - m->prev_bw_bytes;
+ m->prev_bw_bytes = cur_bytes;

- cur_bw = (chunks * hw_res->mon_scale) >> 20;
+ cur_bw = bytes / SZ_1M;

if (m->delta_comp)
m->delta_bw = abs(cur_bw - m->prev_bw);
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index cb857f753322..0cf5b20c6ddf 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -227,7 +227,7 @@ void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d);
* @d: domain that the counter should be read from.
* @rmid: rmid of the counter to read.
* @eventid: eventid to read, e.g. L3 occupancy.
- * @val: result of the counter read in chunks.
+ * @val: result of the counter read in bytes.
*
* Call from process context on a CPU that belongs to domain @d.
*
--
2.30.2