Hi Babu, On 3/11/25 1:35 PM, Moger, Babu wrote: > Hi All, > > On 3/10/25 22:51, Reinette Chatre wrote: >> >> >> On 3/10/25 6:44 PM, Moger, Babu wrote: >>> Hi Tony, >>> >>> On 3/10/2025 6:22 PM, Luck, Tony wrote: >>>> On Mon, Mar 10, 2025 at 05:48:44PM -0500, Moger, Babu wrote: >>>>> Hi All, >>>>> >>>>> On 3/5/2025 1:34 PM, Moger, Babu wrote: >>>>>> Hi Peter, >>>>>> >>>>>> On 3/5/25 04:40, Peter Newman wrote: >>>>>>> Hi Babu, >>>>>>> >>>>>>> On Tue, Mar 4, 2025 at 10:49 PM Moger, Babu <babu.moger@xxxxxxx> wrote: >>>>>>>> >>>>>>>> Hi Peter, >>>>>>>> >>>>>>>> On 3/4/25 10:44, Peter Newman wrote: >>>>>>>>> On Mon, Mar 3, 2025 at 8:16 PM Moger, Babu <babu.moger@xxxxxxx> wrote: >>>>>>>>>> >>>>>>>>>> Hi Peter/Reinette, >>>>>>>>>> >>>>>>>>>> On 2/26/25 07:27, Peter Newman wrote: >>>>>>>>>>> Hi Babu, >>>>>>>>>>> >>>>>>>>>>> On Tue, Feb 25, 2025 at 10:31 PM Moger, Babu <babu.moger@xxxxxxx> wrote: >>>>>>>>>>>> >>>>>>>>>>>> Hi Peter, >>>>>>>>>>>> >>>>>>>>>>>> On 2/25/25 11:11, Peter Newman wrote: >>>>>>>>>>>>> Hi Reinette, >>>>>>>>>>>>> >>>>>>>>>>>>> On Fri, Feb 21, 2025 at 11:43 PM Reinette Chatre >>>>>>>>>>>>> <reinette.chatre@xxxxxxxxx> wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>> Hi Peter, >>>>>>>>>>>>>> >>>>>>>>>>>>>> On 2/21/25 5:12 AM, Peter Newman wrote: >>>>>>>>>>>>>>> On Thu, Feb 20, 2025 at 7:36 PM Reinette Chatre >>>>>>>>>>>>>>> <reinette.chatre@xxxxxxxxx> wrote: >>>>>>>>>>>>>>>> On 2/20/25 6:53 AM, Peter Newman wrote: >>>>>>>>>>>>>>>>> On Wed, Feb 19, 2025 at 7:21 PM Reinette Chatre >>>>>>>>>>>>>>>>> <reinette.chatre@xxxxxxxxx> wrote: >>>>>>>>>>>>>>>>>> On 2/19/25 3:28 AM, Peter Newman wrote: >>>>>>>>>>>>>>>>>>> On Tue, Feb 18, 2025 at 6:50 PM Reinette Chatre >>>>>>>>>>>>>>>>>>> <reinette.chatre@xxxxxxxxx> wrote: >>>>>>>>>>>>>>>>>>>> On 2/17/25 2:26 AM, Peter Newman wrote: >>>>>>>>>>>>>>>>>>>>> On Fri, Feb 14, 2025 at 8:18 PM Reinette Chatre >>>>>>>>>>>>>>>>>>>>> <reinette.chatre@xxxxxxxxx> wrote: >>>>>>>>>>>>>>>>>>>>>> On 2/14/25 10:31 AM, Moger, Babu wrote: >>>>>>>>>>>>>>>>>>>>>>> On 2/14/2025 12:26 AM, Reinette Chatre wrote: >>>>>>>>>>>>>>>>>>>>>>>> On 2/13/25 9:37 AM, Dave Martin wrote: >>>>>>>>>>>>>>>>>>>>>>>>> On Wed, Feb 12, 2025 at 03:33:31PM -0800, Reinette Chatre wrote: >>>>>>>>>>>>>>>>>>>>>>>>>> On 2/12/25 9:46 AM, Dave Martin wrote: >>>>>>>>>>>>>>>>>>>>>>>>>>> On Wed, Jan 22, 2025 at 02:20:08PM -0600, Babu Moger wrote: >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> (quoting relevant parts with goal to focus discussion on new possible syntax) >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> I see the support for MPAM events distinct from the support of assignable counters. >>>>>>>>>>>>>>>>>>>>>>>>>> Once the MPAM events are sorted, I think that they can be assigned with existing interface. >>>>>>>>>>>>>>>>>>>>>>>>>> Please help me understand if you see it differently. >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> Doing so would need to come up with alphabetical letters for these events, >>>>>>>>>>>>>>>>>>>>>>>>>> which seems to be needed for your proposal also? If we use possible flags of: >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> mbm_local_read_bytes a >>>>>>>>>>>>>>>>>>>>>>>>>> mbm_local_write_bytes b >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> Then mbm_assign_control can be used as: >>>>>>>>>>>>>>>>>>>>>>>>>> # echo '//0=ab;1=b' >/sys/fs/resctrl/info/L3_MON/mbm_assign_control >>>>>>>>>>>>>>>>>>>>>>>>>> # cat /sys/fs/resctrl/mon_data/mon_L3_00/mbm_local_read_bytes >>>>>>>>>>>>>>>>>>>>>>>>>> <value> >>>>>>>>>>>>>>>>>>>>>>>>>> # cat /sys/fs/resctrl/mon_data/mon_L3_00/mbm_local_bytes >>>>>>>>>>>>>>>>>>>>>>>>>> <sum of mbm_local_read_bytes and mbm_local_write_bytes> >>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>> One issue would be when resctrl needs to support more than 26 events (no more flags available), >>>>>>>>>>>>>>>>>>>>>>>>>> assuming that upper case would be used for "shared" counters (unless this interface is defined >>>>>>>>>>>>>>>>>>>>>>>>>> differently and only few uppercase letters used for it). Would this be too low of a limit? >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> As mentioned above, one possible issue with existing interface is that >>>>>>>>>>>>>>>>>>>>>> it is limited to 26 events (assuming only lower case letters are used). The limit >>>>>>>>>>>>>>>>>>>>>> is low enough to be of concern. >>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>> The events which can be monitored by a single counter on ABMC and MPAM >>>>>>>>>>>>>>>>>>>>> so far are combinable, so 26 counters per group today means it limits >>>>>>>>>>>>>>>>>>>>> breaking down MBM traffic for each group 26 ways. If a user complained >>>>>>>>>>>>>>>>>>>>> that a 26-way breakdown of a group's MBM traffic was limiting their >>>>>>>>>>>>>>>>>>>>> investigation, I would question whether they know what they're looking >>>>>>>>>>>>>>>>>>>>> for. >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> The key here is "so far" as well as the focus on MBM only. >>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>> It is impossible for me to predict what we will see in a couple of years >>>>>>>>>>>>>>>>>>>> from Intel RDT, AMD PQoS, and Arm MPAM that now all rely on resctrl interface >>>>>>>>>>>>>>>>>>>> to support their users. Just looking at the Intel RDT spec the event register >>>>>>>>>>>>>>>>>>>> has space for 32 events for each "CPU agent" resource. That does not take into >>>>>>>>>>>>>>>>>>>> account the "non-CPU agents" that are enumerated via ACPI. Tony already mentioned >>>>>>>>>>>>>>>>>>>> that he is working on patches [1] that will add new events and shared the idea >>>>>>>>>>>>>>>>>>>> that we may be trending to support "perf" like events associated with RMID. I >>>>>>>>>>>>>>>>>>>> expect AMD PQoS and Arm MPAM to provide related enhancements to support their >>>>>>>>>>>>>>>>>>>> customers. >>>>>>>>>>>>>>>>>>>> This all makes me think that resctrl should be ready to support more events than 26. >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> I was thinking of the letters as representing a reusable, user-defined >>>>>>>>>>>>>>>>>>> event-set for applying to a single counter rather than as individual >>>>>>>>>>>>>>>>>>> events, since MPAM and ABMC allow us to choose the set of events each >>>>>>>>>>>>>>>>>>> one counts. Wherever we define the letters, we could use more symbolic >>>>>>>>>>>>>>>>>>> event names. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> Thank you for clarifying. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> In the letters as events model, choosing the events assigned to a >>>>>>>>>>>>>>>>>>> group wouldn't be enough information, since we would want to control >>>>>>>>>>>>>>>>>>> which events should share a counter and which should be counted by >>>>>>>>>>>>>>>>>>> separate counters. I think the amount of information that would need >>>>>>>>>>>>>>>>>>> to be encoded into mbm_assign_control to represent the level of >>>>>>>>>>>>>>>>>>> configurability supported by hardware would quickly get out of hand. >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> Maybe as an example, one counter for all reads, one counter for all >>>>>>>>>>>>>>>>>>> writes in ABMC would look like... >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> (L3_QOS_ABMC_CFG.BwType field names below) >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> (per domain) >>>>>>>>>>>>>>>>>>> group 0: >>>>>>>>>>>>>>>>>>> counter 0: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>>>>> counter 1: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>>>>> group 1: >>>>>>>>>>>>>>>>>>> counter 2: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>>>>> counter 3: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>>>>> ... >>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> I think this may also be what Dave was heading towards in [2] but in that >>>>>>>>>>>>>>>>>> example and above the counter configuration appears to be global. You do mention >>>>>>>>>>>>>>>>>> "configurability supported by hardware" so I wonder if per-domain counter >>>>>>>>>>>>>>>>>> configuration is a requirement? >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> If it's global and we want a particular group to be watched by more >>>>>>>>>>>>>>>>> counters, I wouldn't want this to result in allocating more counters >>>>>>>>>>>>>>>>> for that group in all domains, or allocating counters in domains where >>>>>>>>>>>>>>>>> they're not needed. I want to encourage my users to avoid allocating >>>>>>>>>>>>>>>>> monitoring resources in domains where a job is not allowed to run so >>>>>>>>>>>>>>>>> there's less pressure on the counters. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> In Dave's proposal it looks like global configuration means >>>>>>>>>>>>>>>>> globally-defined "named counter configurations", which works because >>>>>>>>>>>>>>>>> it's really per-domain assignment of the configurations to however >>>>>>>>>>>>>>>>> many counters the group needs in each domain. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> I think I am becoming lost. Would a global configuration not break your >>>>>>>>>>>>>>>> view of "event-set applied to a single counter"? If a counter is configured >>>>>>>>>>>>>>>> globally then it would not make it possible to support the full configurability >>>>>>>>>>>>>>>> of the hardware. >>>>>>>>>>>>>>>> Before I add more confusion, let me try with an example that builds on your >>>>>>>>>>>>>>>> earlier example copied below: >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>> (per domain) >>>>>>>>>>>>>>>>>>> group 0: >>>>>>>>>>>>>>>>>>> counter 0: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>>>>> counter 1: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>>>>> group 1: >>>>>>>>>>>>>>>>>>> counter 2: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>>>>> counter 3: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>>>>> ... >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> Since the above states "per domain" I rewrite the example to highlight that as >>>>>>>>>>>>>>>> I understand it: >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> group 0: >>>>>>>>>>>>>>>> domain 0: >>>>>>>>>>>>>>>> counter 0: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>> counter 1: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>> domain 1: >>>>>>>>>>>>>>>> counter 0: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>> counter 1: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>> group 1: >>>>>>>>>>>>>>>> domain 0: >>>>>>>>>>>>>>>> counter 2: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>> counter 3: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>> domain 1: >>>>>>>>>>>>>>>> counter 2: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>> counter 3: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> You mention that you do not want counters to be allocated in domains that they >>>>>>>>>>>>>>>> are not needed in. So, let's say group 0 does not need counter 0 and counter 1 >>>>>>>>>>>>>>>> in domain 1, resulting in: >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> group 0: >>>>>>>>>>>>>>>> domain 0: >>>>>>>>>>>>>>>> counter 0: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>> counter 1: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>> group 1: >>>>>>>>>>>>>>>> domain 0: >>>>>>>>>>>>>>>> counter 2: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>> counter 3: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>> domain 1: >>>>>>>>>>>>>>>> counter 2: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>> counter 3: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> With counter 0 and counter 1 available in domain 1, these counters could >>>>>>>>>>>>>>>> theoretically be configured to give group 1 more data in domain 1: >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> group 0: >>>>>>>>>>>>>>>> domain 0: >>>>>>>>>>>>>>>> counter 0: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>> counter 1: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>> group 1: >>>>>>>>>>>>>>>> domain 0: >>>>>>>>>>>>>>>> counter 2: LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>> counter 3: VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>>> domain 1: >>>>>>>>>>>>>>>> counter 0: LclFill,RmtFill >>>>>>>>>>>>>>>> counter 1: LclNTWr,RmtNTWr >>>>>>>>>>>>>>>> counter 2: LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>>> counter 3: VictimBW >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> The counters are shown with different per-domain configurations that seems to >>>>>>>>>>>>>>>> match with earlier goals of (a) choose events counted by each counter and >>>>>>>>>>>>>>>> (b) do not allocate counters in domains where they are not needed. As I >>>>>>>>>>>>>>>> understand the above does contradict global counter configuration though. >>>>>>>>>>>>>>>> Or do you mean that only the *name* of the counter is global and then >>>>>>>>>>>>>>>> that it is reconfigured as part of every assignment? >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Yes, I meant only the *name* is global. I assume based on a particular >>>>>>>>>>>>>>> system configuration, the user will settle on a handful of useful >>>>>>>>>>>>>>> groupings to count. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Perhaps mbm_assign_control syntax is the clearest way to express an example... >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> # define global configurations (in ABMC terms), not necessarily in this >>>>>>>>>>>>>>> # syntax and probably not in the mbm_assign_control file. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> r=LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>>>>>>> w=VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> # legacy "total" configuration, effectively r+w >>>>>>>>>>>>>>> t=LclFill,RmtFill,LclSlowFill,RmtSlowFill,VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> /group0/0=t;1=t >>>>>>>>>>>>>>> /group1/0=t;1=t >>>>>>>>>>>>>>> /group2/0=_;1=t >>>>>>>>>>>>>>> /group3/0=rw;1=_ >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> - group2 is restricted to domain 0 >>>>>>>>>>>>>>> - group3 is restricted to domain 1 >>>>>>>>>>>>>>> - the rest are unrestricted >>>>>>>>>>>>>>> - In group3, we decided we need to separate read and write traffic >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> This consumes 4 counters in domain 0 and 3 counters in domain 1. >>>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> I see. Thank you for the example. >>>>>>>>>>>>>> >>>>>>>>>>>>>> resctrl supports per-domain configurations with the following possible when >>>>>>>>>>>>>> using mbm_total_bytes_config and mbm_local_bytes_config: >>>>>>>>>>>>>> >>>>>>>>>>>>>> t(domain 0)=LclFill,RmtFill,LclSlowFill,RmtSlowFill,VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>> t(domain 1)=LclFill,RmtFill,VictimBW,LclNTWr,RmtNTWr >>>>>>>>>>>>>> >>>>>>>>>>>>>> /group0/0=t;1=t >>>>>>>>>>>>>> /group1/0=t;1=t >>>>>>>>>>>>>> >>>>>>>>>>>>>> Even though the flags are identical in all domains, the assigned counters will >>>>>>>>>>>>>> be configured differently in each domain. >>>>>>>>>>>>>> >>>>>>>>>>>>>> With this supported by hardware and currently also supported by resctrl it seems >>>>>>>>>>>>>> reasonable to carry this forward to what will be supported next. >>>>>>>>>>>>> >>>>>>>>>>>>> The hardware supports both a per-domain mode, where all groups in a >>>>>>>>>>>>> domain use the same configurations and are limited to two events per >>>>>>>>>>>>> group and a per-group mode where every group can be configured and >>>>>>>>>>>>> assigned freely. This series is using the legacy counter access mode >>>>>>>>>>>>> where only counters whose BwType matches an instance of QOS_EVT_CFG_n >>>>>>>>>>>>> in the domain can be read. If we chose to read the assigned counter >>>>>>>>>>>>> directly (QM_EVTSEL[ExtendedEvtID]=1, QM_EVTSEL[EvtID]=L3CacheABMC) >>>>>>>>>>>>> rather than asking the hardware to find the counter by RMID, we would >>>>>>>>>>>>> not be limited to 2 counters per group/domain and the hardware would >>>>>>>>>>>>> have the same flexibility as on MPAM. >>>>>>>>>>>> >>>>>>>>>>>> In extended mode, the contents of a specific counter can be read by >>>>>>>>>>>> setting the following fields in QM_EVTSEL: [ExtendedEvtID]=1, >>>>>>>>>>>> [EvtID]=L3CacheABMC and setting [RMID] to the desired counter ID. Reading >>>>>>>>>>>> QM_CTR will then return the contents of the specified counter. >>>>>>>>>>>> >>>>>>>>>>>> It is documented below. >>>>>>>>>>>> https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/programmer-references/24593.pdf >>>>>>>>>>>> Section: 19.3.3.3 Assignable Bandwidth Monitoring (ABMC) >>>>>>>>>>>> >>>>>>>>>>>> We previously discussed this with you (off the public list) and I >>>>>>>>>>>> initially proposed the extended assignment mode. >>>>>>>>>>>> >>>>>>>>>>>> Yes, the extended mode allows greater flexibility by enabling multiple >>>>>>>>>>>> counters to be assigned to the same group, rather than being limited to >>>>>>>>>>>> just two. >>>>>>>>>>>> >>>>>>>>>>>> However, the challenge is that we currently lack the necessary interfaces >>>>>>>>>>>> to configure multiple events per group. Without these interfaces, the >>>>>>>>>>>> extended mode is not practical at this time. >>>>>>>>>>>> >>>>>>>>>>>> Therefore, we ultimately agreed to use the legacy mode, as it does not >>>>>>>>>>>> require modifications to the existing interface, allowing us to continue >>>>>>>>>>>> using it as is. >>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> (I might have said something confusing in my last messages because I >>>>>>>>>>>>> had forgotten that I switched to the extended assignment mode when >>>>>>>>>>>>> prototyping with soft-ABMC and MPAM.) >>>>>>>>>>>>> >>>>>>>>>>>>> Forcing all groups on a domain to share the same 2 counter >>>>>>>>>>>>> configurations would not be acceptable for us, as the example I gave >>>>>>>>>>>>> earlier is one I've already been asked about. >>>>>>>>>>>> >>>>>>>>>>>> I don’t see this as a blocker. It should be considered an extension to the >>>>>>>>>>>> current ABMC series. We can easily build on top of this series once we >>>>>>>>>>>> finalize how to configure the multiple event interface for each group. >>>>>>>>>>> >>>>>>>>>>> I don't think it is, either. Only being able to use ABMC to assign >>>>>>>>>>> counters is fine for our use as an incremental step. My longer-term >>>>>>>>>>> concern is the domain-scoped mbm_total_bytes_config and >>>>>>>>>>> mbm_local_bytes_config files, but they were introduced with BMEC, so >>>>>>>>>>> there's already an expectation that the files are present when BMEC is >>>>>>>>>>> supported. >>>>>>>>>>> >>>>>>>>>>> On ABMC hardware that also supports BMEC, I'm concerned about enabling >>>>>>>>>>> ABMC when only the BMEC-style event configuration interface exists. >>>>>>>>>>> The scope of my issue is just whether enabling "full" ABMC support >>>>>>>>>>> will require an additional opt-in, since that could remove the BMEC >>>>>>>>>>> interface. If it does, it's something we can live with. >>>>>>>>>> >>>>>>>>>> As you know, this series is currently blocked without further feedback. >>>>>>>>>> >>>>>>>>>> I’d like to begin reworking these patches to incorporate Peter’s feedback. >>>>>>>>>> Any input or suggestions would be appreciated. >>>>>>>>>> >>>>>>>>>> Here’s what we’ve learned so far: >>>>>>>>>> >>>>>>>>>> 1. Assignments should be independent of BMEC. >>>>>>>>>> 2. We should be able to specify multiple event types to a counter (e.g., >>>>>>>>>> read, write, victimBM, etc.). This is also called shared counter >>>>>>>>>> 3. There should be an option to assign events per domain. >>>>>>>>>> 4. Currently, only two counters can be assigned per group, but the design >>>>>>>>>> should allow flexibility to assign more in the future as the interface >>>>>>>>>> evolves. >>>>>>>>>> 5. Utilize the extended RMID read mode. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Here is my proposal using Peter's earlier example: >>>>>>>>>> >>>>>>>>>> # define event configurations >>>>>>>>>> >>>>>>>>>> ======================================================== >>>>>>>>>> Bits Mnemonics Description >>>>>>>>>> ==== ======================================================== >>>>>>>>>> 6 VictimBW Dirty Victims from all types of memory >>>>>>>>>> 5 RmtSlowFill Reads to slow memory in the non-local NUMA domain >>>>>>>>>> 4 LclSlowFill Reads to slow memory in the local NUMA domain >>>>>>>>>> 3 RmtNTWr Non-temporal writes to non-local NUMA domain >>>>>>>>>> 2 LclNTWr Non-temporal writes to local NUMA domain >>>>>>>>>> 1 mtFill Reads to memory in the non-local NUMA domain >>>>>>>>>> 0 LclFill Reads to memory in the local NUMA domain >>>>>>>>>> ==== ======================================================== >>>>>>>>>> >>>>>>>>>> #Define flags based on combination of above event types. >>>>>>>>>> >>>>>>>>>> t = LclFill,RmtFill,LclSlowFill,RmtSlowFill,VictimBW,LclNTWr,RmtNTWr >>>>>>>>>> l = LclFill, LclNTWr, LclSlowFill >>>>>>>>>> r = LclFill,RmtFill,LclSlowFill,RmtSlowFill >>>>>>>>>> w = VictimBW,LclNTWr,RmtNTWr >>>>>>>>>> v = VictimBW >>>>>>>>>> >>>>>>>>>> Peter suggested the following format earlier : >>>>>>>>>> >>>>>>>>>> /group0/0=t;1=t >>>>>>>>>> /group1/0=t;1=t >>>>>>>>>> /group2/0=_;1=t >>>>>>>>>> /group3/0=rw;1=_ >>>>>>>>> >>>>>>>>> After some inquiries within Google, it sounds like nobody has invested >>>>>>>>> much into the current mbm_assign_control format yet, so it would be >>>>>>>>> best to drop it and distribute the configuration around the filesystem >>>>>>>>> hierarchy[1], which should allow us to produce something more flexible >>>>>>>>> and cleaner to implement. >>>>>>>>> >>>>>>>>> Roughly what I had in mind: >>>>>>>>> >>>>>>>>> Use mkdir in a info/<resource>_MON subdirectory to create free-form >>>>>>>>> names for the assignable configurations rather than being restricted >>>>>>>>> to single letters. In the resulting directory, populate a file where >>>>>>>>> we can specify the set of events the config should represent. I think >>>>>>>>> we should use symbolic names for the events rather than raw BMEC field >>>>>>>>> values. Moving forward we could come up with portable names for common >>>>>>>>> events and only support the BMEC names on AMD machines for users who >>>>>>>>> want specific events and don't care about portability. >>>>>>>> >>>>>>>> >>>>>>>> I’m still processing this. Let me start with some initial questions. >>>>>>>> >>>>>>>> So, we are creating event configurations here, which seems reasonable. >>>>>>>> >>>>>>>> Yes, we should use portable names and are not limited to BMEC names. >>>>>>>> >>>>>>>> How many configurations should we allow? Do we know? >>>>>>> >>>>>>> Do we need an upper limit? >>>>>> >>>>>> I think so. This needs to be maintained in some data structure. We can >>>>>> start with 2 default configurations for now. >> >> There is a big difference between no upper limit and 2. The hardware is >> capable of supporting per-domain configurations so more flexibility is >> certainly possible. Consider the example presented by Peter in: >> https://lore.kernel.org/lkml/CALPaoCi0mFZ9TycyNs+SCR+2tuRJovQ2809jYMun4HtC64hJmA@xxxxxxxxxxxxxx/ >> >>>>>>>>> Next, put assignment-control file nodes in per-domain directories >>>>>>>>> (i.e., mon_data/mon_L3_00/assign_{exclusive,shared}). Writing a >>>>>>>>> counter-configuration name into the file would then allocate a counter >>>>>>>>> in the domain, apply the named configuration, and monitor the parent >>>>>>>>> group-directory. We can also put a group/resource-scoped assign_* file >>>>>>>>> higher in the hierarchy to make it easier for users who want to >>>>>>>>> configure all domains the same for a group. >>>>>>>> >>>>>>>> What is the difference between shared and exclusive? >>>>>>> >>>>>>> Shared assignment[1] means that non-exclusively-assigned counters in >>>>>>> each domain will be scheduled round-robin to the groups requesting >>>>>>> shared access to a counter. In my tests, I assigned the counters long >>>>>>> enough to produce a single 1-second MB/s sample for the per-domain >>>>>>> aggregation files[2]. >>>>>>> >>>>>>> These do not need to be implemented immediately, but knowing that they >>>>>>> work addresses the overhead and scalability concerns of reassigning >>>>>>> counters and reading their values. >>>>>> >>>>>> Ok. Lets focus on exclusive assignments for now. >>>>>> >>>>>>> >>>>>>>> >>>>>>>> Having three files—assign_shared, assign_exclusive, and unassign—for each >>>>>>>> domain seems excessive. In a system with 32 groups and 12 domains, this >>>>>>>> results in 32 × 12 × 3 files, which is quite large. >>>>>>>> >>>>>>>> There should be a more efficient way to handle this. >>>>>>>> >>>>>>>> Initially, we started with a group-level file for this interface, but it >>>>>>>> was rejected due to the high number of sysfs calls, making it inefficient. >>>>>>> >>>>>>> I had rejected it due to the high-frequency of access of a large >>>>>>> number of files, which has since been addressed by shared assignment >>>>>>> (or automatic reassignment) and aggregated mbps files. >>>>>> >>>>>> I think we should address this as well. Creating three extra files for >>>>>> each group isn’t ideal when there are more efficient alternatives. >>>>>> >>>>>>> >>>>>>>> >>>>>>>> Additionally, how can we list all assignments with a single sysfs call? >>>>>>>> >>>>>>>> That was another problem we need to address. >>>>>>> >>>>>>> This is not a requirement I was aware of. If the user forgot where >>>>>>> they assigned counters (or forgot to disable auto-assignment), they >>>>>>> can read multiple sysfs nodes to remind themselves. >>>>>> >>>>>> I suggest, we should provide users with an option to list the assignments >>>>>> of all groups in a single command. As the number of groups increases, it >>>>>> becomes cumbersome to query each group individually. >>>>>> >>>>>> To achieve this, we can reuse our existing mbm_assign_control interface >>>>>> for this purpose. More details on this below. >>>>>> >>>>>>>> >>>>>>>> >>>>>>>>> >>>>>>>>> The configuration names listed in assign_* would result in files of >>>>>>>>> the same name in the appropriate mon_data domain directories from >>>>>>>>> which the count values can be read. >>>>>>>>> >>>>>>>>> # mkdir info/L3_MON/counter_configs/mbm_local_bytes >>>>>>>>> # echo LclFill > info/L3_MON/counter_configs/mbm_local_bytes/event_filter >>>>>>>>> # echo LclNTWr > info/L3_MON/counter_configs/mbm_local_bytes/event_filter >>>>>>>>> # echo LclSlowFill > info/L3_MON/counter_configs/mbm_local_bytes/event_filter >>>>>>>>> # cat info/L3_MON/counter_configs/mbm_local_bytes/event_filter >>>>>>>>> LclFill >>>>>>>>> LclNTWr >>>>>>>>> LclSlowFill >>>>>>>> >>>>>>>> I feel we can just have the configs. event_filter file is not required. >>>>>>> >>>>>>> That's right, I forgot that we can implement kernfs_ops::open(). I was >>>>>>> only looking at struct kernfs_syscall_ops >>>>>>> >>>>>>>> >>>>>>>> #cat info/L3_MON/counter_configs/mbm_local_bytes >>>>>>>> LclFill <-rename these to generic names. >>>>>>>> LclNTWr >>>>>>>> LclSlowFill >>>>>>>> >>>>>>> >>>>>>> I think portable and non-portable event names should both be available >>>>>>> as options. There are simple bandwidth measurement mechanisms that >>>>>>> will be applied in general, but when they turn up an issue, it can >>>>>>> often lead to a more focused investigation, requiring more precise >>>>>>> events. >>>>>> >>>>>> I aggree. We should provide both portable and non-portable event names. >>>>>> >>>>>> Here is my draft proposal based on the discussion so far and reusing some >>>>>> of the current interface. Idea here is to start with basic assigment >>>>>> feature with options to enhance it in the future. Feel free to >>>>>> comment/suggest. >>>>>> >>>>>> 1. Event configurations will be in >>>>>> /sys/fs/resctrl/info/L3_MON/counter_configs/. >>>>>> >>>>>> There will be two pre-defined configurations by default. >>>>>> >>>>>> #cat /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_total_bytes >>>>>> LclFill, LclNTWr,LclSlowFill,VictimBM,RmtSlowFill,LclSlowFill,RmtFill >>>>>> >>>>>> #cat /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_local_bytes >>>>>> LclFill, LclNTWr, LclSlowFill >>>>>> >>>>>> 2. Users will have options to update these configurations. >>>>>> >>>>>> #echo "LclFill, LclNTWr, RmtFill" > >>>>>> /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_local_bytes >>>> >>>> This part seems odd to me. Now the "mbm_local_bytes" files aren't >>>> reporting "local_bytes" any more. They report something different, >>>> and users only know if they come to check the options currently >>>> configured in this file. Changing the contents without changing >>>> the name seems confusing to me. >>> >>> It is the same behaviour right now with BMEC. It is configurable. >>> By default it is mbm_local_bytes, but users can configure whatever they want to monitor using /info/L3_MON/mbm_local_bytes_config. >>> >>> We can continue the same behaviour with ABMC, but the configuration will be in /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_local_bytes. >> >> This could be supported by following Peter's original proposal where the name >> of the counter configuration is provided by the user via a mkdir: >> https://lore.kernel.org/lkml/CALPaoCiii0vXOF06mfV=kVLBzhfNo0SFqt4kQGwGSGVUqvr2Dg@xxxxxxxxxxxxxx/ >> >> As he mentioned there could be pre-populated mbm_local_bytes/mbm_total_bytes. > > Sure. We can do that. I was thinking in the first phase, just provide the > default pre-defined configuration and option to update the configuration. > > We can add the mkdir support later. That way we can provide basic ABMC > support without too much code complexity with mkdir support. This is not clear to me how you envision the "first phase". Is it what you proposed above, for example: #echo "LclFill, LclNTWr, RmtFill" > /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_local_bytes In above the counter configuration name is a file. How could mkdir support be added to this later if there are already files present? > >> >>> >>>> >>>>>> >>>>>> # #cat /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_local_bytes >>>>>> LclFill, LclNTWr, RmtFill >>>>>> >>>>>> 3. The default configurations will be used when user mounts the resctrl. >>>>>> >>>>>> mount -t resctrl resctrl /sys/fs/resctrl/ >>>>>> mkdir /sys/fs/resctrl/test/ >>>>>> >>>>>> 4. The resctrl group/domains can be in one of these assingnment states. >>>>>> e: Exclusive >>>>>> s: Shared >>>>>> u: Unassigned >>>>>> >>>>>> Exclusive mode is supported now. Shared mode will be supported in the >>>>>> future. >>>>>> >>>>>> 5. We can use the current /sys/fs/resctrl/info/L3_MON/mbm_assign_control >>>>>> to list the assignment state of all the groups. >>>>>> >>>>>> Format: >>>>>> "<CTRL_MON group>/<MON group>/<confguration>:<domain_id>=<assign state>" >>>>>> >>>>>> # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_control >>>>>> test//mbm_total_bytes:0=e;1=e >>>>>> test//mbm_local_bytes:0=e;1=e >>>>>> //mbm_total_bytes:0=e;1=e >>>>>> //mbm_local_bytes:0=e;1=e >> >> This would make mbm_assign_control even more unwieldy and quicker to exceed a >> page of data (these examples never seem to reflect those AMD systems with the many >> L3 domains). How to handle resctrl files larger than 4KB needs to be well understood >> and solved when/if going this route. > > This problem is not specific this series. I feel it is a generic problem > to many of the semilar interfaces. I dont know how it is addressed. May > have to investigate on this. Any pointers would be helpful. Dave Martin already did a lot of analysis here. What other pointers do you need? > > >> >> There seems to be two opinions about this file at moment. Would it be possible to >> summarize the discussion with pros/cons raised to make an informed selection? >> I understand that Google as represented by Peter no longer requires/requests this >> file but the motivation for this change seems new and does not seem to reduce the >> original motivation for this file. We may also want to separate requirements for reading >> from and writing to this file. > > Yea. We can just use mbm_assign_control for reading the assignment states. > > Summary: We have two proposals. > > First one from Peter: > > https://lore.kernel.org/lkml/CALPaoCiii0vXOF06mfV=kVLBzhfNo0SFqt4kQGwGSGVUqvr2Dg@xxxxxxxxxxxxxx/ > > > Pros > a. Allows flexible creation of free-form names for assignable > configurations, stored in info/L3_MON/counter_configs/. > > b. Events can be accessed using corresponding free-form names in the > mon_data directory, making it clear to users what each event represents. > > > Cons: > a. Requires three separate files for assignment in each group > (assign_exclusive, assign_shared, unassign), which might be excessive. > > b. No built-in listing support, meaning users must query each group > individually to check assignment states. > > > Second Proposal (Mine) > > https://lore.kernel.org/lkml/a4ab53b5-03be-4299-8853-e86270d46f2e@xxxxxxx/ > > Pros: > > a. Maintains the flexibility of free-form names for assignable > configurations (info/L3_MON/counter_configs/). > > b. Events remain accessible via free-form names in mon_data, ensuring > clarity on their purpose. > > c. Adds the ability to list assignment states for all groups in a single > command. > > Cons: > a. Potential buffer overflow issues when handling a large number of > groups and domains and code complexity to fix the issue. > > > Third Option: A Hybrid Approach > > We could combine elements from both proposals: > > a. Retain the free-form naming approach for assignable configurations in > info/L3_MON/counter_configs/. > > b. Use the assignment method from the first proposal: > $mkdir test > $echo mbm_local_bytes > test/mon_data/mon_L3_00/assign_exclusive > > c. Introduce listing support via the info/L3_MON/mbm_assign_control > interface, enabling users to read assignment states for all groups in one > place. Only reading support. > > >> >>>>>> >>>>>> 6. Users can modify the assignment state by writing to mbm_assign_control. >>>>>> >>>>>> Format: >>>>>> “<CTRL_MON group>/<MON group>/<configuration>:<domain_id>=<assign state>” >>>>>> >>>>>> #echo "test//mbm_local_bytes:0=e;1=e" > >>>>>> /sys/fs/resctrl/info/L3_MON/mbm_assign_control >>>>>> >>>>>> #echo "test//mbm_local_bytes:0=u;1=u" > >>>>>> /sys/fs/resctrl/info/L3_MON/mbm_assign_control >>>>>> >>>>>> # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_control >>>>>> test//mbm_total_bytes:0=u;1=u >>>>>> test//mbm_local_bytes:0=u;1=u >>>>>> //mbm_total_bytes:0=e;1=e >>>>>> //mbm_local_bytes:0=e;1=e >>>>>> >>>>>> The corresponding events will be read in >>>>>> >>>>>> /sys/fs/resctrl/mon_data/mon_L3_00/mbm_total_bytes >>>>>> /sys/fs/resctrl/mon_data/mon_L3_01/mbm_total_bytes >>>>>> /sys/fs/resctrl/mon_data/mon_L3_00/mbm_local_bytes >>>>>> /sys/fs/resctrl/mon_data/mon_L3_01/mbm_local_bytes >>>>>> /sys/fs/resctrl/test/mon_data/mon_L3_00/mbm_total_bytes >>>>>> /sys/fs/resctrl/test/mon_data/mon_L3_01/mbm_total_bytes >>>>>> /sys/fs/resctrl/test/mon_data/mon_L3_00/mbm_local_bytes >>>>>> /sys/fs/resctrl/test/mon_data/mon_L3_01/mbm_local_bytes >>>>>> >>>>>> 7. In the first stage, only two configurations(mbm_total_bytes and >>>>>> mbm_local_bytes) will be supported. >>>>>> >>>>>> 8. In the future, there will be options to create multiple configurations >>>>>> and corresponding directory will be created in >>>>>> /sysf/fs/resctrl/test/mon_data/mon_L3_00/<configation name>. >>>> >>>> Would this be done by creating a new file in the /sys/fs/resctrl/info/L3_MON/counter_configs >>>> directory? Like this: >>>> >>>> # echo "LclFill, LclNTWr, RmtFill" > >>>> /sys/fs/resctrl/info/L3_MON/counter_configs/cache_stuff >>>> >>>> This seems OK (dependent on the user picking meaningful names for >>>> the set of attributes picked ... but if they want to name this >>>> monitor file "brian" then they have to live with any confusion >>>> that they bring on themselves). >>>> >>>> Would this involve an extension to kernfs? I don't see a function >>>> pointer callback for file creation in kernfs_syscall_ops. >>>> >>>>>> >>>>> >>>>> I know you are all busy with multiple series going on parallel. I am still >>>>> waiting for the inputs on this. It will be great if you can spend some time >>>>> on this to see if we can find common ground on the interface. >>>>> >>>>> Thanks >>>>> Babu >>>> >>>> -Tony >>>> >>> >>> >>> thanks >>> Babu >> >> Reinette >> >> >
