Re: [PATCH V2 08/10] x86/resctrl: Support pseudo-lock regions spanning resources

Borislav Petkov
2019-08-07T09:17:41Z

On Tue, Jul 30, 2019 at 10:29:42AM -0700, Reinette Chatre wrote:
> Currently cache pseudo-locked regions only consider one cache level but
> cache pseudo-locked regions may span multiple cache levels.
>
> In preparation for support of pseudo-locked regions spanning multiple
> cache levels pseudo-lock 'portions' are introduced. A 'portion' of a
> pseudo-locked region is the portion of a pseudo-locked region that
> belongs to a specific resource. Each pseudo-locked portion is identified
> with the resource (for example, L2 or L3 cache), the domain (the
> specific cache instance), and the capacity bitmask that specifies which
> region of the cache is used by the pseudo-locked region.
>
> In support of pseudo-locked regions spanning multiple cache levels a
> pseudo-locked region could have multiple 'portions' but in this
> introduction only single portions are allowed.
>
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
> ---
> arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 26 +++-
> arch/x86/kernel/cpu/resctrl/internal.h | 32 ++--
> arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 180 ++++++++++++++++------
> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 44 ++++--
> 4 files changed, 211 insertions(+), 71 deletions(-)

This patch kinda got pretty big and is hard to review. Can
you split it pls? The addition of pseudo_lock_portion and
pseudo_lock_single_portion_valid() look like a separate patch to me.

> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> index a0383ff80afe..a60fb38a4d20 100644
> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> @@ -207,7 +207,7 @@ int parse_cbm(struct rdt_parse_data *data, struct rdt_resource *r,
> * hierarchy.
> */
> if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP &&
> - rdtgroup_pseudo_locked_in_hierarchy(d)) {
> + rdtgroup_pseudo_locked_in_hierarchy(rdtgrp, d)) {
> rdt_last_cmd_puts("Pseudo-locked region in hierarchy\n");
> return -EINVAL;
> }
> @@ -282,6 +282,7 @@ static int parse_line(char *line, struct rdt_resource *r,
> if (r->parse_ctrlval(&data, r, d))
> return -EINVAL;
> if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
> + struct pseudo_lock_portion *p;
> /*
> * In pseudo-locking setup mode and just
> * parsed a valid CBM that should be
> @@ -290,9 +291,15 @@ static int parse_line(char *line, struct rdt_resource *r,
> * the required initialization for single
> * region and return.
> */
> - rdtgrp->plr->r = r;
> - rdtgrp->plr->d_id = d->id;
> - rdtgrp->plr->cbm = d->new_ctrl;
> + p = kzalloc(sizeof(*p), GFP_KERNEL);
> + if (!p) {
> + rdt_last_cmd_puts("Unable to allocate memory for pseudo-lock portion\n");
> + return -ENOMEM;
> + }
> + p->r = r;
> + p->d_id = d->id;
> + p->cbm = d->new_ctrl;
> + list_add(&p->list, &rdtgrp->plr->portions);
> return 0;
> }

Looking at the indentation level of this, it is basically begging to
become a separate, helper function...

> goto next;
> @@ -410,8 +417,11 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
> goto out;
> }
> ret = rdtgroup_parse_resource(resname, tok, rdtgrp);
> - if (ret)
> + if (ret) {
> + if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP)
> + pseudo_lock_region_clear(rdtgrp->plr);
> goto out;
> + }
> }
>
> for_each_alloc_enabled_rdt_resource(r) {
> @@ -459,6 +469,7 @@ static void show_doms(struct seq_file *s, struct rdt_resource *r, int closid)
> int rdtgroup_schemata_show(struct kernfs_open_file *of,
> struct seq_file *s, void *v)
> {
> + struct pseudo_lock_portion *p;
> struct rdtgroup *rdtgrp;
> struct rdt_resource *r;
> int ret = 0;
> @@ -470,8 +481,9 @@ int rdtgroup_schemata_show(struct kernfs_open_file *of,
> for_each_alloc_enabled_rdt_resource(r)
> seq_printf(s, "%s:uninitialized\n", r->name);
> } else if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED) {
> - seq_printf(s, "%s:%d=%x\n", rdtgrp->plr->r->name,
> - rdtgrp->plr->d_id, rdtgrp->plr->cbm);
> + list_for_each_entry(p, &rdtgrp->plr->portions, list)
> + seq_printf(s, "%s:%d=%x\n", p->r->name, p->d_id,
> + p->cbm);

Shouldn't this say that those are portions now?

> } else {
> closid = rdtgrp->closid;
> for_each_alloc_enabled_rdt_resource(r) {
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 892f38899dda..b041029d4de1 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -145,13 +145,27 @@ struct mongroup {
> u32 rmid;
> };
>
> +/**
> + * struct pseudo_lock_portion - portion of a pseudo-lock region on one resource
> + * @r: RDT resource to which this pseudo-locked portion
> + * belongs
> + * @d_id: ID of cache instance to which this pseudo-locked portion
> + * belongs
> + * @cbm: bitmask of the pseudo-locked portion
> + * @list: Entry in the list of pseudo-locked portion
> + * belonging to the pseudo-locked region
> + */
> +struct pseudo_lock_portion {
> + struct rdt_resource *r;
> + int d_id;
> + u32 cbm;
> + struct list_head list;
> +};
> +
> /**
> * struct pseudo_lock_region - pseudo-lock region information
> - * @r: RDT resource to which this pseudo-locked region
> - * belongs
> - * @d_id: ID of cache instance to which this pseudo-locked region
> - * belongs
> - * @cbm: bitmask of the pseudo-locked region
> + * @portions: list of portions across different resources that
> + * are associated with this pseudo-locked region
> * @lock_thread_wq: waitqueue used to wait on the pseudo-locking thread
> * completion
> * @thread_done: variable used by waitqueue to test if pseudo-locking
> @@ -168,9 +182,7 @@ struct mongroup {
> * @pm_reqs: Power management QoS requests related to this region
> */
> struct pseudo_lock_region {
> - struct rdt_resource *r;
> - int d_id;
> - u32 cbm;
> + struct list_head portions;
> wait_queue_head_t lock_thread_wq;
> int thread_done;
> int cpu;
> @@ -569,11 +581,13 @@ bool rdtgroup_cbm_overlaps_pseudo_locked(struct rdt_resource *r,
> struct rdt_domain *d,
> unsigned long cbm);
> u32 rdtgroup_pseudo_locked_bits(struct rdt_resource *r, struct rdt_domain *d);
> -bool rdtgroup_pseudo_locked_in_hierarchy(struct rdt_domain *d);
> +bool rdtgroup_pseudo_locked_in_hierarchy(struct rdtgroup *selfgrp,
> + struct rdt_domain *d);
> int rdt_pseudo_lock_init(void);
> void rdt_pseudo_lock_release(void);
> int rdtgroup_pseudo_lock_create(struct rdtgroup *rdtgrp);
> void rdtgroup_pseudo_lock_remove(struct rdtgroup *rdtgrp);
> +void pseudo_lock_region_clear(struct pseudo_lock_region *plr);
> struct rdt_domain *get_domain_from_cpu(int cpu, struct rdt_resource *r);
> int update_domains(struct rdt_resource *r, int closid);
> int closids_supported(void);
> diff --git a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> index 733cb7f34948..717ea26e325b 100644
> --- a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> +++ b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> @@ -270,28 +270,85 @@ static int pseudo_lock_cstates_constrain(struct pseudo_lock_region *plr,
> *
> * Return: void
> */
> -static void pseudo_lock_region_clear(struct pseudo_lock_region *plr)
> +void pseudo_lock_region_clear(struct pseudo_lock_region *plr)
> {
> + struct pseudo_lock_portion *p, *tmp;
> +
> plr->size = 0;
> plr->line_size = 0;
> kfree(plr->kmem);
> plr->kmem = NULL;
> - plr->r = NULL;
> - plr->d_id = -1;
> - plr->cbm = 0;
> pseudo_lock_cstates_relax(plr);
> + if (!list_empty(&plr->portions)) {
> + list_for_each_entry_safe(p, tmp, &plr->portions, list) {
> + list_del(&p->list);
> + kfree(p);
> + }
> + }
> plr->debugfs_dir = NULL;
> }
>
> +/**
> + * pseudo_lock_single_portion_valid - Verify properties of pseudo-lock region
> + * @plr: the main pseudo-lock region
> + * @p: the single portion that makes up the pseudo-locked region
> + *
> + * Verify and initialize properties of the pseudo-locked region.
> + *
> + * Return: -1 if portion of cache unable to be used for pseudo-locking
> + * 0 if portion of cache can be used for pseudo-locking, in
> + * addition the CPU on which pseudo-locking will be performed will
> + * be initialized as well as the size and cache line size of the region
> + */
> +static int pseudo_lock_single_portion_valid(struct pseudo_lock_region *plr,
> + struct pseudo_lock_portion *p)
> +{
> + struct rdt_domain *d;
> +
> + d = rdt_find_domain(p->r, p->d_id, NULL);
> + if (IS_ERR_OR_NULL(d)) {
> + rdt_last_cmd_puts("Cannot find cache domain\n");
> + return -1;
> + }
> +
> + plr->cpu = cpumask_first(&d->cpu_mask);
> + if (!cpu_online(plr->cpu)) {
> + rdt_last_cmd_printf("CPU %u not online\n", plr->cpu);
> + goto err_cpu;
> + }
> +
> + plr->line_size = get_cache_line_size(plr->cpu, p->r->cache_level);
> + if (plr->line_size == 0) {
> + rdt_last_cmd_puts("Unable to compute cache line length\n");
> + goto err_cpu;
> + }
> +
> + if (pseudo_lock_cstates_constrain(plr, &d->cpu_mask)) {
> + rdt_last_cmd_puts("Cannot limit C-states\n");
> + goto err_line;
> + }
> +
> + plr->size = rdtgroup_cbm_to_size(p->r, d, p->cbm);
> +
> + return 0;
> +
> +err_line:
> + plr->line_size = 0;
> +err_cpu:
> + plr->cpu = 0;
> + return -1;
> +}
> +
> /**
> * pseudo_lock_region_init - Initialize pseudo-lock region information
> * @plr: pseudo-lock region
> *
> * Called after user provided a schemata to be pseudo-locked. From the
> * schemata the &struct pseudo_lock_region is on entry already initialized
> - * with the resource, domain, and capacity bitmask. Here the information
> - * required for pseudo-locking is deduced from this data and &struct
> - * pseudo_lock_region initialized further. This information includes:
> + * with the resource, domain, and capacity bitmask. Here the
> + * provided data is validated and information required for pseudo-locking
> + * deduced, and &struct pseudo_lock_region initialized further. This
> + * information includes:
> * - size in bytes of the region to be pseudo-locked
> * - cache line size to know the stride with which data needs to be accessed
> * to be pseudo-locked
> @@ -303,44 +360,50 @@ static void pseudo_lock_region_clear(struct pseudo_lock_region *plr)
> */
> static int pseudo_lock_region_init(struct pseudo_lock_region *plr)
> {
> - struct rdt_domain *d;
> + struct rdt_resource *l3_resource = &rdt_resources_all[RDT_RESOURCE_L3];
> + struct pseudo_lock_portion *p;
> int ret;
>
> - /* Pick the first cpu we find that is associated with the cache. */
> - d = rdt_find_domain(plr->r, plr->d_id, NULL);
> - if (IS_ERR_OR_NULL(d)) {
> - rdt_last_cmd_puts("Cache domain offline\n");
> - ret = -ENODEV;
> + if (list_empty(&plr->portions)) {
> + rdt_last_cmd_puts("No pseudo-lock portions provided\n");
> goto out_region;

Not return?

Do you need to clear anything in an not even initialized plr?

> }
>
> - plr->cpu = cpumask_first(&d->cpu_mask);
> -
> - if (!cpu_online(plr->cpu)) {
> - rdt_last_cmd_printf("CPU %u associated with cache not online\n",
> - plr->cpu);
> - ret = -ENODEV;
> - goto out_region;
> + /* Cache Pseudo-Locking only supported on L2 and L3 resources */
> + list_for_each_entry(p, &plr->portions, list) {
> + if (p->r->rid != RDT_RESOURCE_L2 &&
> + p->r->rid != RDT_RESOURCE_L3) {
> + rdt_last_cmd_puts("Unsupported resource\n");
> + goto out_region;
> + }
> }
>
> - plr->line_size = get_cache_line_size(plr->cpu, plr->r->cache_level);
> - if (plr->line_size == 0) {
> - rdt_last_cmd_puts("Unable to determine cache line size\n");
> - ret = -1;
> - goto out_region;
> + /*
> + * If only one resource requested to be pseudo-locked then:
> + * - Just a L3 cache portion is valid
> + * - Just a L2 cache portion on system without L3 cache is valid
> + */
> + if (list_is_singular(&plr->portions)) {
> + p = list_first_entry(&plr->portions, struct pseudo_lock_portion,
> + list);

Let that line stick out.

> + if (p->r->rid == RDT_RESOURCE_L3 ||
> + (p->r->rid == RDT_RESOURCE_L2 &&
> + !l3_resource->alloc_capable)) {
> + ret = pseudo_lock_single_portion_valid(plr, p);
> + if (ret < 0)
> + goto out_region;
> + return 0;
> + } else {
> + rdt_last_cmd_puts("Invalid resource or just L2 provided when L3 is required\n");
> + goto out_region;
> + }
> + } else {
> + rdt_last_cmd_puts("Multiple pseudo-lock portions unsupported\n");
> }
>
> - plr->size = rdtgroup_cbm_to_size(plr->r, d, plr->cbm);
> -
> - ret = pseudo_lock_cstates_constrain(plr, &d->cpu_mask);
> - if (ret < 0)
> - goto out_region;
> -
> - return 0;
> -
> out_region:
> pseudo_lock_region_clear(plr);
> - return ret;
> + return -1;
> }
>

Yap, this patch is doing too many things at once and splitting it would help.

Thx.

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.