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Message-ID: <Yp++A0tuEqAN7eHo@fyu1.sc.intel.com>
Date: Tue, 7 Jun 2022 14:07:15 -0700
From: Fenghua Yu <fenghua.yu@...el.com>
To: James Morse <james.morse@....com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
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,
D Scott Phillips OS <scott@...amperecomputing.com>,
lcherian@...vell.com, bobo.shaobowang@...wei.com,
tan.shaopeng@...itsu.com, Jamie Iles <quic_jiles@...cinc.com>,
Cristian Marussi <cristian.marussi@....com>,
Xin Hao <xhao@...ux.alibaba.com>, xingxin.hx@...nanolis.org,
baolin.wang@...ux.alibaba.com
Subject: Re: [PATCH v4 16/21] x86/resctrl: Pass the required parameters into
resctrl_arch_rmid_read()
Hi, James,
On Tue, Apr 12, 2022 at 12:44:14PM +0000, James Morse wrote:
> resctrl_arch_rmid_read() is intended as the function that an
> architecture agnostic resctrl filesystem driver can use to
> read a value in bytes from a hardware register. Currently the function
> returns the MBM values in chunks directly from hardware.
>
> To convert this to bytes, some correction and overflow calculations
> are needed. These depend on the resource and domain structures.
> Overflow detection requires the old chunks value. None of this
> is available to resctrl_arch_rmid_read(). MPAM requires the
> resource and domain structures to find the MMIO device that holds
> the registers.
>
> Pass the resource and domain to resctrl_arch_rmid_read(). This makes
> rmid_dirty() too big.
rmid_dirty() is not called by resctrl_arch_rmid_read(). Why does parring r and d
make rmid_dirty() too big?
> Instead merge it with its only caller, and the
> name is kept as a local variable.
>
> Reviewed-by: Jamie Iles <quic_jiles@...cinc.com>
> Tested-by: Xin Hao <xhao@...ux.alibaba.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Tested-by: Cristian Marussi <cristian.marussi@....com>
> Signed-off-by: James Morse <james.morse@....com>
> ---
> Changes since v3:
> * Added comment about where resctrl_arch_rmid_read() can be called from.
>
> Changes since v2:
> * Typos.
> * Kerneldoc fixes.
>
> This is all a little noisy for __mon_event_count(), as the switch
> statement work is now before the resctrl_arch_rmid_read() call.
> ---
> arch/x86/kernel/cpu/resctrl/monitor.c | 31 +++++++++++++++------------
> include/linux/resctrl.h | 18 +++++++++++++++-
> 2 files changed, 34 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 20c54cbadc0c..81cc7587b598 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -167,10 +167,14 @@ void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_domain *d,
> memset(am, 0, sizeof(*am));
> }
>
> -int resctrl_arch_rmid_read(u32 rmid, enum resctrl_event_id eventid, u64 *val)
> +int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
> + u32 rmid, enum resctrl_event_id eventid, u64 *val)
Can this be a concise interface by just adding one more parameter "rr"?
int resctrl_arch_rmid_read(struct rmid_read *rr, u32 rmid, u64 *val);
> {
> u64 msr_val;
Then inside the API, add:
struct rdt_resource *r = rr->r;
struct rdt_domain *d = rr->d;
struct rdt_resource r = rr->r;
enum resctrl_event_id evtid = rr->evtid;
>
> + if (!cpumask_test_cpu(smp_processor_id(), &d->cpu_mask))
> + return -EINVAL;
> +
> /*
> * As per the SDM, when IA32_QM_EVTSEL.EvtID (bits 7:0) is configured
> * with a valid event code for supported resource type and the bits
> @@ -192,16 +196,6 @@ int resctrl_arch_rmid_read(u32 rmid, enum resctrl_event_id eventid, u64 *val)
> return 0;
> }
>
> -static bool rmid_dirty(struct rmid_entry *entry)
> -{
> - u64 val = 0;
> -
> - if (resctrl_arch_rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID, &val))
> - return true;
> -
> - return val >= resctrl_cqm_threshold;
> -}
> -
> /*
> * Check the RMIDs that are marked as busy for this domain. If the
> * reported LLC occupancy is below the threshold clear the busy bit and
> @@ -213,6 +207,8 @@ void __check_limbo(struct rdt_domain *d, bool force_free)
> struct rmid_entry *entry;
> struct rdt_resource *r;
> u32 crmid = 1, nrmid;
> + bool rmid_dirty;
> + u64 val = 0;
>
> r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
>
> @@ -228,7 +224,14 @@ void __check_limbo(struct rdt_domain *d, bool force_free)
> break;
>
> entry = __rmid_entry(nrmid);
> - if (force_free || !rmid_dirty(entry)) {
> +
> + if (resctrl_arch_rmid_read(r, d, entry->rmid,
> + QOS_L3_OCCUP_EVENT_ID, &val))
> + rmid_dirty = true;
> + else
> + rmid_dirty = (val >= resctrl_cqm_threshold);
> +
> + if (force_free || !rmid_dirty) {
> clear_bit(entry->rmid, d->rmid_busy_llc);
> if (!--entry->busy) {
> rmid_limbo_count--;
> @@ -278,7 +281,7 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
> cpu = get_cpu();
> list_for_each_entry(d, &r->domains, list) {
> if (cpumask_test_cpu(cpu, &d->cpu_mask)) {
> - err = resctrl_arch_rmid_read(entry->rmid,
> + err = resctrl_arch_rmid_read(r, d, entry->rmid,
> QOS_L3_OCCUP_EVENT_ID,
> &val);
> if (err || val <= resctrl_cqm_threshold)
> @@ -336,7 +339,7 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr)
> if (rr->first)
> resctrl_arch_reset_rmid(rr->r, rr->d, rmid, rr->evtid);
>
> - rr->err = resctrl_arch_rmid_read(rmid, rr->evtid, &tval);
> + rr->err = resctrl_arch_rmid_read(rr->r, rr->d, rmid, rr->evtid, &tval);
Is resctrl_arch_rmid_read(rr, rmid, &tval) concise and better?
> if (rr->err)
> return rr->err;
>
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 70112dbfa128..cc6311a40582 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -219,7 +219,23 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_domain *d,
> u32 closid, enum resctrl_conf_type type);
> int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d);
> void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d);
> -int resctrl_arch_rmid_read(u32 rmid, enum resctrl_event_id eventid, u64 *res);
> +
> +/**
> + * resctrl_arch_rmid_read() - Read the eventid counter corresponding to rmid
> + * for this resource and domain.
> + * @r: resource that the counter should be read from.
> + * @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.
> + *
> + * Call from process context on a CPU that belongs to domain @d.
> + *
> + * Return:
> + * 0 on success, or -EIO, -EINVAL etc on error.
> + */
> +int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
> + u32 rmid, enum resctrl_event_id eventid, u64 *val);
Then it's a concise API:
int resctrl_arch_rmid_read(struct rmid_read *rr, u32 rmid, u64 *val);
r, d and eventid can be easily retrieved from rr inside the API implementation.
>
> /**
> * resctrl_arch_reset_rmid() - Reset any private state associated with rmid
> --
> 2.30.2
>
Thanks.
-Fenghua
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