On 2023-10-27 at 16:30:38 +0300, Ilpo Järvinen wrote: >On Fri, 27 Oct 2023, Maciej Wieczór-Retman wrote: > >> On 2023-10-24 at 12:26:31 +0300, Ilpo Järvinen wrote: >> >Resource id is acquired differently depending on CPU. AMD tests use id >> >from L3 cache, whereas CPUs from other vendors base the id on topology >> >package id. In order to support L2 CAT test, this has to be >> >generalized. >> > >> >The driver side code seems to get the resource ids from cache ids so >> >the approach used by the AMD branch seems to match the kernel-side >> >code. It will also work with L2 resource IDs as long as the cache level >> >is generalized. >> > >> >Using the topology id was always fragile due to mismatch with the >> >kernel-side way to acquire the resource id. It got incorrect resource >> >id, e.g., when Cluster-on-Die (CoD) is enabled for CPU (but CoD is not >> >well suited for resctrl in the first place so it has not been a big >> >issues if test don't work correctly with it). >> >> "not been a big issues" -> "not been a big issue"? >> >> "if test don't work correctly" -> "if test doesn't work correctly" / "if tests >> don't work correctly"? >> >> > >> >Taking all the above into account, generalize the resource id >> >calculation by taking it from the cache id and do not hard-code the >> >cache level. >> >> In x86/resctrl files group of CPUs sharing a resctrl resource is called a >> domain. Because of that I think "resource id" terms should be substituted with >> "domain id" to match core resctrl code. > >Okay, I was just using the terminology which pre-existed in the selftest >code. > >I've really tried to look how I should call it but things were quite >inconsistent. The selftest uses resource id and reads it from cache id. >Documentation uses "instances of that resource" or "cache id" or "domain >x". > > >Documentation/arch/x86/resctrl.rst is very misleading btw and should be >IMHO updated: > >Memory bandwidth Allocation (default mode) >------------------------------------------ > >Memory b/w domain is L3 cache. >:: > > MB:<cache_id0>=bandwidth0;<cache_id1>=bandwidth1;... > >It claims "domain" is L3 cache (and the value we're talking about is >called "cache_id" here which is what you just called "domain id"). I >suppose it should say "b/w resource is L3 cache"? > I believe so. After some looking around it looks like the "L3 domain" naming is also present in rdtgroup.c:mkdir_mondata_all() and "mon_data" description in the docs: Docs: "mon_data": This contains a set of files organized by L3 domain and by RDT event. E.g. on a system with two L3 domains there will rdtgroup.c: /* * This creates a directory mon_data which contains the monitored data. * * mon_data has one directory for each domain which are named * in the format mon_<domain_name>_<domain_id>. For ex: A mon_data * with L3 domain looks as below: * ./mon_data: * mon_L3_00 * mon_L3_01 * mon_L3_02 * ... * * Each domain directory has one file per event: * ./mon_L3_00/: * llc_occupancy * */ static int mkdir_mondata_all(struct kernfs_node *parent_kn, struct rdtgroup *prgrp, struct kernfs_node **dest_kn) >From the reading I've done on resctrl my understanding was that L2/L3 are resources that can be shared between domains. -- Kind regards Maciej Wieczór-Retman
