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Message-ID: <7e401723-4cb6-43c4-ad4c-8e3a28639718@amd.com>
Date: Thu, 9 Nov 2023 14:39:16 -0600
From: "Moger, Babu" <babu.moger@....com>
To: James Morse <james.morse@....com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Cc: 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>,
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,
baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
dfustini@...libre.com, amitsinght@...vell.com
Subject: Re: [PATCH v7 10/24] x86/resctrl: Allocate the cleanest CLOSID by
searching closid_num_dirty_rmid
Hi James,
On 10/25/23 13:03, 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.
>
> Instead of allocating the first free CLOSID, on architectures where
> CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID is enabled, search
> closid_num_dirty_rmid[] to find the cleanest CLOSID.
>
> The CLOSID found is returned to closid_alloc() for the free list
> to be updated.
>
> Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Tested-by: Peter Newman <peternewman@...gle.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> Signed-off-by: James Morse <james.morse@....com>
Reviewed-by: Babu Moger <babu.moger@....com>
> ---
> Changes since v4:
> * Dropped stale section from comment
>
> Changes since v5:
> * Renamed some variables.
>
> No changes since v6
> ---
> arch/x86/kernel/cpu/resctrl/internal.h | 2 ++
> arch/x86/kernel/cpu/resctrl/monitor.c | 45 ++++++++++++++++++++++++++
> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 19 ++++++++---
> 3 files changed, 61 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 2f1d4f141dab..521afa016b05 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -568,5 +568,7 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
> void __init thread_throttle_mode_init(void);
> void __init mbm_config_rftype_init(const char *config);
> void rdt_staged_configs_clear(void);
> +bool closid_allocated(unsigned int closid);
> +int resctrl_find_cleanest_closid(void);
>
> #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 9a07707d3eb4..cf512d4d383e 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -386,6 +386,51 @@ static struct rmid_entry *resctrl_find_free_rmid(u32 closid)
> return ERR_PTR(-ENOSPC);
> }
>
> +/**
> + * resctrl_find_cleanest_closid() - Find a CLOSID where all the associated
> + * RMID are clean, or the CLOSID that has
> + * the most clean RMID.
> + *
> + * MPAM's equivalent of RMID are per-CLOSID, meaning a freshly allocated CLOSID
> + * may not be able to allocate clean RMID. To avoid this the allocator will
> + * choose the CLOSID with the most clean RMID.
> + *
> + * When the CLOSID and RMID are independent numbers, the first free CLOSID will
> + * be returned.
> + */
> +int resctrl_find_cleanest_closid(void)
> +{
> + u32 cleanest_closid = ~0;
> + int i = 0;
> +
> + lockdep_assert_held(&rdtgroup_mutex);
> +
> + if (!IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID))
> + return -EIO;
> +
> + for (i = 0; i < closids_supported(); i++) {
> + int num_dirty;
> +
> + if (closid_allocated(i))
> + continue;
> +
> + num_dirty = closid_num_dirty_rmid[i];
> + if (num_dirty == 0)
> + return i;
> +
> + if (cleanest_closid == ~0)
> + cleanest_closid = i;
> +
> + if (num_dirty < closid_num_dirty_rmid[cleanest_closid])
> + cleanest_closid = i;
> + }
> +
> + if (cleanest_closid == ~0)
> + return -ENOSPC;
> +
> + return cleanest_closid;
> +}
> +
> /*
> * For MPAM the RMID value is not unique, and has to be considered with
> * the CLOSID. The (CLOSID, RMID) pair is allocated on all domains, which
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index f6051a3e7262..0b9bd5f0f60d 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -137,13 +137,22 @@ static void closid_init(void)
>
> static int closid_alloc(void)
> {
> - u32 closid = ffs(closid_free_map);
> + int cleanest_closid;
> + u32 closid;
>
> lockdep_assert_held(&rdtgroup_mutex);
>
> - if (closid == 0)
> - return -ENOSPC;
> - closid--;
> + if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID)) {
> + cleanest_closid = resctrl_find_cleanest_closid();
> + if (cleanest_closid < 0)
> + return cleanest_closid;
> + closid = cleanest_closid;
> + } else {
> + closid = ffs(closid_free_map);
> + if (closid == 0)
> + return -ENOSPC;
> + closid--;
> + }
> __clear_bit(closid, &closid_free_map);
>
> return closid;
> @@ -163,7 +172,7 @@ void closid_free(int closid)
> * Return: true if @closid is currently associated with a resource group,
> * false if @closid is free
> */
> -static bool closid_allocated(unsigned int closid)
> +bool closid_allocated(unsigned int closid)
> {
> lockdep_assert_held(&rdtgroup_mutex);
>
--
Thanks
Babu Moger
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