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Message-ID: <4d8773f7-4219-0bc5-e7df-1be81cba05e7@intel.com>
Date: Mon, 14 Aug 2023 19:37:35 -0700
From: Fenghua Yu <fenghua.yu@...el.com>
To: James Morse <james.morse@....com>, <x86@...nel.org>,
<linux-kernel@...r.kernel.org>
CC: 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>,
<carl@...amperecomputing.com>, <lcherian@...vell.com>,
<bobo.shaobowang@...wei.com>, <tan.shaopeng@...itsu.com>,
<xingxin.hx@...nanolis.org>, <baolin.wang@...ux.alibaba.com>,
Jamie Iles <quic_jiles@...cinc.com>,
Xin Hao <xhao@...ux.alibaba.com>, <peternewman@...gle.com>,
<dfustini@...libre.com>
Subject: Re: [PATCH v5 06/24] x86/resctrl: Track the number of dirty RMID a
CLOSID has
Hi, James,
On 7/28/23 09:42, James Morse wrote:
> MPAM's PMG bits extend its PARTID space, meaning the same PMG value can be
> used for different control groups.
>
> This means once a CLOSID is allocated, all its monitoring ids may still be
> dirty, and held in limbo.
>
> Keep track of the number of RMID held in limbo each CLOSID has. This will
> allow a future helper to find the 'cleanest' CLOSID when allocating.
>
> The array is only needed when CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID is
> defined. This will never be the case on x86.
>
> Signed-off-by: James Morse <james.morse@....com>
> ---
> Changes since v4:
> * Moved closid_num_dirty_rmid[] update under entry->busy check
> * Take the mutex in dom_data_init() as the caller doesn't.
> ---
> arch/x86/kernel/cpu/resctrl/monitor.c | 49 +++++++++++++++++++++++----
> 1 file changed, 42 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index de91ca781d9f..44addc0126fc 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -43,6 +43,13 @@ struct rmid_entry {
> */
> static LIST_HEAD(rmid_free_lru);
>
Better to add:
#if CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID
> +/**
> + * @closid_num_dirty_rmid The number of dirty RMID each CLOSID has.
> + * Only allocated when CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID is defined.
> + * Indexed by CLOSID. Protected by rdtgroup_mutex.
> + */
> +static int *closid_num_dirty_rmid;
#endif
Then the global variable won't exist on x86 to avoid confusion and space.
Some code related to the CONFIG also needs to be changed accordingly.
> +
> /**
> * @rmid_limbo_count count of currently unused but (potentially)
> * dirty RMIDs.
> @@ -285,6 +292,17 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
> return 0;
> }
>
> +static void limbo_release_entry(struct rmid_entry *entry)
> +{
> + lockdep_assert_held(&rdtgroup_mutex);
> +
> + rmid_limbo_count--;
> + list_add_tail(&entry->list, &rmid_free_lru);
> +
> + if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID))
> + closid_num_dirty_rmid[entry->closid]--;
Maybe define some helpers (along with other similar ones) in resctrl.h
like this:
#ifdef CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID
static inline void closid_num_dirty_rmid_dec(struct rmid_entry *entry)
{
closid_num_dirty_rmid[entry->closid]--;
}
...
#else
static inline void closid_num_dirty_rmid_dec(struct rmid_entry *unused)
{
}
...
#endif
Then directly call the helper here:
+ closid_num_dirty_rmid_dec(entry);
On x86 this is noop without occupy any space and cleaner code.
> +}
> +
> /*
> * 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
> @@ -321,10 +339,8 @@ void __check_limbo(struct rdt_domain *d, bool force_free)
>
> if (force_free || !rmid_dirty) {
> clear_bit(idx, d->rmid_busy_llc);
> - if (!--entry->busy) {
> - rmid_limbo_count--;
> - list_add_tail(&entry->list, &rmid_free_lru);
> - }
> + if (!--entry->busy)
> + limbo_release_entry(entry);
> }
> cur_idx = idx + 1;
> }
> @@ -391,6 +407,8 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
> u64 val = 0;
> u32 idx;
>
> + lockdep_assert_held(&rdtgroup_mutex);
> +
> idx = resctrl_arch_rmid_idx_encode(entry->closid, entry->rmid);
>
> entry->busy = 0;
> @@ -416,9 +434,11 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
> }
> put_cpu();
>
> - if (entry->busy)
> + if (entry->busy) {
> rmid_limbo_count++;
> - else
> + if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID))
> + closid_num_dirty_rmid[entry->closid]++;
Ditto.
> + } else
> list_add_tail(&entry->list, &rmid_free_lru);
> }
>
> @@ -782,13 +802,28 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms)
> static int dom_data_init(struct rdt_resource *r)
> {
> u32 idx_limit = resctrl_arch_system_num_rmid_idx();
> + u32 num_closid = resctrl_arch_get_num_closid(r);
> struct rmid_entry *entry = NULL;
> u32 idx;
> int i;
>
> + if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID)) {
> + int *tmp;
> +
> + tmp = kcalloc(num_closid, sizeof(int), GFP_KERNEL);
> + if (!tmp)
> + return -ENOMEM;
> +
> + mutex_lock(&rdtgroup_mutex);
data_init() is called in __init. No need to lock here, right?
> + closid_num_dirty_rmid = tmp;
> + mutex_unlock(&rdtgroup_mutex);
> + }
> +
This code is also can be defined as a helper in resctrl.h.
> rmid_ptrs = kcalloc(idx_limit, sizeof(struct rmid_entry), GFP_KERNEL);
> - if (!rmid_ptrs)
> + if (!rmid_ptrs) {
> + kfree(closid_num_dirty_rmid);
> return -ENOMEM;
> + }
>
> for (i = 0; i < idx_limit; i++) {
> entry = &rmid_ptrs[i];
Thanks.
-Fenghua
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