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Message-ID: <8881fa05-e69c-6599-4925-2dc9ee83eebd@arm.com> Date: Mon, 22 Jan 2024 18:06:40 +0000 From: James Morse <james.morse@....com> To: babu.moger@....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 v8 00/24] x86/resctrl: monitored closid+rmid together, separate arch/fs locking Hi Babu, On 03/01/2024 19:42, Moger, Babu wrote: > Hi James, > Tested the series. Looks good. Thanks - this was on an AMD machine right? (I've not got access to one of those, so I'm always nervous about something I may have missed!) Thanks, James > Thanks > Babu > > On 12/15/23 11:43, James Morse wrote: >> Some of the changes this version are: >> * Fixed a bounds checking bug in cpumask_any_housekeeping(), >> * Moved the kfree() of rmid_ptrs[] later, >> >> Changes are noted in each patch, I've not added 'no changes' notes >> if these need double checking anyway. I'll try again next series. >> >> ~ >> >> This series does two things, it changes resctrl to call resctrl_arch_rmid_read() >> in a way that works for MPAM, and it separates the locking so that the arch code >> and filesystem code don't have to share a mutex. I tried to split this as two >> series, but these touch similar call sites, so it would create more work. >> >> (What's MPAM? See the cover letter of the first series. [1]) >> >> On x86 the RMID is an independent number. MPAMs equivalent is PMG, but this >> isn't an independent number - it extends the PARTID (same as CLOSID) space >> with bits that aren't used to select the configuration. The monitors can >> then be told to match specific PMG values, allowing monitor-groups to be >> created. >> >> But, MPAM expects the monitors to always monitor by PARTID. The >> Cache-storage-utilisation counters can only work this way. >> (In the MPAM spec not setting the MATCH_PARTID bit is made CONSTRAINED >> UNPREDICTABLE - which is Arm's term to mean portable software can't rely on >> this) >> >> It gets worse, as some SoCs may have very few PMG bits. I've seen the >> datasheet for one that has a single bit of PMG space. >> >> To be usable, MPAM's counters always need the PARTID and the PMG. >> For resctrl, this means always making the CLOSID available when the RMID >> is used. >> >> To ensure RMID are always unique, this series combines the CLOSID and RMID >> into an index, and manages RMID based on that. For x86, the index and RMID >> would always be the same. >> >> >> Currently the architecture specific code in the cpuhp callbacks takes the >> rdtgroup_mutex. This means the filesystem code would have to export this >> lock, resulting in an ill-defined interface between the two, and the possibility >> of cross-architecture lock-ordering head aches. >> >> The second part of this series adds a domain_list_lock to protect writes to the >> domain list, and protects the domain list with RCU - or cpus_read_lock(). >> >> Use of RCU is to allow lockless readers of the domain list. To get MPAMs monitors >> working, its very likely they'll need to be plumbed up to perf. An uncore PMU >> driver would need to be a lockless reader of the domain list. >> >> >> >> This series is based on v6.7-rc2, and can be retrieved from: >> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git mpam/monitors_and_locking/v8 >> >> Bugs welcome, >> >> Thanks, >> >> James >> >> [1] https://lore.kernel.org/lkml/20210728170637.25610-1-james.morse@arm.com/ >> [v1] https://lore.kernel.org/all/20221021131204.5581-1-james.morse@arm.com/ >> [v2] https://lore.kernel.org/lkml/20230113175459.14825-1-james.morse@arm.com/ >> [v3] https://lore.kernel.org/r/20230320172620.18254-1-james.morse@arm.com/ >> [v4] https://lore.kernel.org/r/20230525180209.19497-1-james.morse@arm.com/ >> [v5] https://lore.kernel.org/lkml/20230728164254.27562-1-james.morse@arm.com/ >> [v6] https://lore.kernel.org/all/20230914172138.11977-1-james.morse@arm.com/ >> [v7] https://lore.kernel.org/r/20231025180345.28061-1-james.morse@arm.com/ >> >> James Morse (24): >> tick/nohz: Move tick_nohz_full_mask declaration outside the #ifdef >> x86/resctrl: kfree() rmid_ptrs from resctrl_exit() >> x86/resctrl: Create helper for RMID allocation and mondata dir >> creation >> x86/resctrl: Move rmid allocation out of mkdir_rdt_prepare() >> x86/resctrl: Track the closid with the rmid >> x86/resctrl: Access per-rmid structures by index >> x86/resctrl: Allow RMID allocation to be scoped by CLOSID >> x86/resctrl: Track the number of dirty RMID a CLOSID has >> x86/resctrl: Use __set_bit()/__clear_bit() instead of open coding >> x86/resctrl: Allocate the cleanest CLOSID by searching >> closid_num_dirty_rmid >> x86/resctrl: Move CLOSID/RMID matching and setting to use helpers >> x86/resctrl: Add cpumask_any_housekeeping() for limbo/overflow >> x86/resctrl: Queue mon_event_read() instead of sending an IPI >> x86/resctrl: Allow resctrl_arch_rmid_read() to sleep >> x86/resctrl: Allow arch to allocate memory needed in >> resctrl_arch_rmid_read() >> x86/resctrl: Make resctrl_mounted checks explicit >> x86/resctrl: Move alloc/mon static keys into helpers >> x86/resctrl: Make rdt_enable_key the arch's decision to switch >> x86/resctrl: Add helpers for system wide mon/alloc capable >> x86/resctrl: Add CPU online callback for resctrl work >> x86/resctrl: Allow overflow/limbo handlers to be scheduled on any-but >> cpu >> x86/resctrl: Add CPU offline callback for resctrl work >> x86/resctrl: Move domain helper migration into resctrl_offline_cpu() >> x86/resctrl: Separate arch and fs resctrl locks >> >> arch/x86/include/asm/resctrl.h | 90 +++++ >> arch/x86/kernel/cpu/resctrl/core.c | 102 ++--- >> arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 48 ++- >> arch/x86/kernel/cpu/resctrl/internal.h | 67 +++- >> arch/x86/kernel/cpu/resctrl/monitor.c | 449 +++++++++++++++++----- >> arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 15 +- >> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 359 ++++++++++++----- >> include/linux/resctrl.h | 48 ++- >> include/linux/tick.h | 9 +- >> 9 files changed, 911 insertions(+), 276 deletions(-) >> >
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