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Date: Wed, 23 Mar 2022 16:17:14 -0500
From: Rob Herring <robh@...nel.org>
To: James Morse <james.morse@....com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
Fenghua Yu <fenghua.yu@...el.com>,
Reinette Chatre <reinette.chatre@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
H Peter Anvin <hpa@...or.com>,
Babu Moger <Babu.Moger@....com>,
shameerali.kolothum.thodi@...wei.com,
Jamie Iles <jamie@...iainc.com>,
D Scott Phillips OS <scott@...amperecomputing.com>,
lcherian@...vell.com, bobo.shaobowang@...wei.com,
tan.shaopeng@...itsu.com
Subject: Re: [PATCH v3 21/21] x86/resctrl: Make resctrl_arch_rmid_read()
return values in bytes
On Thu, Feb 17, 2022 at 06:21:10PM +0000, James Morse wrote:
> 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.
>
> Signed-off-by: James Morse <james.morse@....com>
> ---
> arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 6 ++----
> arch/x86/kernel/cpu/resctrl/internal.h | 4 ++--
> arch/x86/kernel/cpu/resctrl/monitor.c | 22 +++++++++-------------
> include/linux/resctrl.h | 2 +-
> 4 files changed, 14 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 e26a4d67e204..d6ce6ce91885 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 when for bandwidth calculation
> + * @prev_bw_bytes: Previous bytes value read when 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 3a6555f49720..437e7db77f93 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -186,7 +186,7 @@ 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;
> @@ -211,10 +211,11 @@ 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);
> + *val = chunks * hw_res->mon_scale;
This can be moved out of the if/else if you make the following change:
> am->prev_msr = msr_val;
> } else {
> - *val = msr_val;
> + *val = msr_val * hw_res->mon_scale;
chunks = msr_val;
> }
>
> return 0;
> @@ -229,7 +230,6 @@ 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;
> @@ -252,7 +252,6 @@ 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);
> }
>
> @@ -296,7 +295,6 @@ 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;
> @@ -308,7 +306,6 @@ 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;
> }
> @@ -400,15 +397,14 @@ static u64 __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 >> 20;
'bytes / SZ_1M' would be more readable and any decent compiler should
optimize a power of 2 divide. But maybe that's a separate change as
there are other cases of bytes to MB.
Rob
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