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If a memory bandwidth associated with a CLOSID is aggressively >>> >>> "a memory bandwidth" -> "memory bandwidth"? >> >> ack. >> >>> >>>> throttled, and it moves into Kernel mode, the Kernel operations are also >>> >>> What does "it" refer to here? From text it seems to be the "CLOSID" but that >>> does not sound right? Should "it" instead be something like "a task with that >>> CLOSID"? >> >> sure. >> >>> >>> "Kernel" -> "kernel"? >> >> ack. >>> >>>> aggressively throttled. This can stall forward progress and eventually >>>> degrade overall system performance. AMD hardware supports a feature >>>> Privilege-Level Zero Association (PLZA) to change the association of the >>>> thread as soon as it begins executing. >>> >>> "change the association of the thread as soon as it begins executing." I am >>> not able to parse this. >> >> How about ? >> >> Customers have identified an issue while using the QoS resource Control >> feature. If memory bandwidth associated with a CLOSID is aggressively >> throttled, and a task with that CLOSID moves into kernel mode, the kernel operations are also aggressively throttled. This can stall forward progress and eventually degrade overall system performance. >> AMD hardware supports a feature Privilege-Level Zero Association (PLZA) >> to change the CPU association at the user-to-kernel transition, so the kernel execution can use a different association than user mode. > > "change the CPU association at the user-to-kernel transition" -> What is this > trying to describe? CPU association of what? > > "a different association"? What does this mean? > Will change it to: AMD hardware supports a feature Privilege-Level Zero Association (PLZA), which allows the CPU’s CLOSID association to be changed during the transition from user mode to kernel mode. This enables the kernel to operate with a different CLOSID than the user mode. >> >> Privilege-Level Zero Association (PLZA) allows the user to specify a> CLOSID and/or RMID associated with execution in Privilege-Level >> Zero. When enabled on a CPU, as the CPU enters Privilege-Level Zero, >> allocation and monitoring for that CPU will be associated with the >> PLZA CLOSID and/or RMID. Otherwise, the CPU will be associated with >> the CLOSID and RMID given by PQR_ASSOC. > > > Sounds like this is vague because MSR_IA32_PQR_PLZA_ASSOC has not been > introduced yet. Could it help to introduce MSR_IA32_PQR_PLZA_ASSOC as > part of this patch and then the changelog can be specific about PLZA > feature introducing this new MSR and how it complements MSR_IA32_PQR_ASSOC? Its probably better to remove the second paragraph. This text can go with the patch which introduces MSR_IA32_PQR_PLZA_ASSOC. With splitting the patch, this will only have cpufeatures changes. > > ... > >>>>   Documentation/admin-guide/kernel-parameters.txt | 2 +- >>>>   arch/x86/include/asm/cpufeatures.h              | 1 + >>>>   arch/x86/kernel/cpu/resctrl/core.c              | 2 ++ >>>>   arch/x86/kernel/cpu/scattered.c                 | 1 + >>> >>> Please split changes to other subsystems and make these changes >>> obvious with their own subject prefix to avoid sneaking changes into >>> other subsystems via resctrl. >>> >> >> Ok. Will be two patches. >> 1. For Documentation/admin-guide/kernel-parameters.txt >> 2.  arch/x86/include/asm/cpufeatures.h >>     arch/x86/kernel/cpu/resctrl/core.c >>     arch/x86/kernel/cpu/scattered.c > > The resctrl changes found in (2) would be documented in (1)? That does not > look right. Why not just split the resctrl changes from the cpufeatures changes? > This would be similar to how you did ABMC enabling. > Sounds good. Thanks Babu