Hi Reinette, On 8/4/25 11:07, Reinette Chatre wrote: > Hi Babu, > > On 7/31/25 3:52 PM, Moger, Babu wrote: >> Hi Reinette, >> >> On 7/21/2025 6:40 PM, Reinette Chatre wrote: >>> Hi Babu, >>> >>> On 7/10/25 10:16 AM, Babu Moger wrote: >>>> "io_alloc" feature in resctrl enables direct insertion of data from I/O >>>> devices into the cache. >>>> >>>> Introduce user interface to enable/disable io_alloc feature. >>> >>> I think it is worth a mention *why* a user may want to disable this feature and >>> why is not just always enabled. Here it can be highlighted that this feature >>> may take resources (CLOSID) away from general (CPU) cache allocation and since >>> this may be scarce enabling user to disable this feature supports different use cases. >>> >> >> Sure. >> >>>> >>>> On AMD systems, io_alloc feature is backed by SDCIAE (L3 Smart Data Cache >>>> Injection Allocation Enforcement). When enabled, SDCIAE directs all SDCI >>>> lines to be placed into the L3 cache partitions specified by the register >>>> corresponding to the highest CLOSID supported by the resource. With CDP >>>> enabled, io_alloc routes I/O traffic using the highest CLOSID assigned to >>>> the instruction cache (L3CODE). >>> >>> This is a lot of architecture specific text for a resctrl fs patch ... I think >>> you are trying to motivate the resctrl fs implementation. Similar motivation >>> as proposed for cover letter can be used here to help explain the implementation >>> choices. >> >> Updated the whole changelog. >> >> fs/resctrl: Add user interface to enable/disable io_alloc feature >> >> "io_alloc" feature in resctrl enables direct insertion of data from I/O >> devices into the cache. >> >> Introduce user interface to enable/disable io_alloc feature. > > The solution should be at end of changelog after description of problem it > solves. Sure. Moved this text below. > >> On AMD systems, when io_alloc is enabled, the highest CLOSID is reserved >> exclusively for I/O allocation traffic and is no longer available for >> general CPU cache allocation. This feature is disabled by default. Users > > Changelog should always be in imperative tone and problem and solution should > be in separate paragraphs (above paragraph mixes problem and solution). > > For example, "Disable "io_alloc" feature by default to ensure all resources are > available for general CPU cache allocation. ..." Although I do not think this is > accurate since this patch does not do this? Yes. Removed the text "This feature is disabled by default." > >> are encouraged to enable it only when running workloads that can benefit >> from this functionality. >> >> Since CLOSIDs are managed by resctrl fs, it is least invasive to make the >> "io_alloc is supported by maximum supported CLOSID" part of the initial >> resctrl fs support for io_alloc. Take care not to expose this use of >> CLOSID for io_alloc to user space so that this is not required from other >> architectures that may support io_alloc differently in the future. >> > > The changelog requirements I refer to are documented in "Changelog" section > of Documentation/process/maintainer-tip.rst. I feel like this should be > familiar to you by now. Sure, Thank you. -- Thanks Babu Moger
