Re: [PATCH v1 8/9] x86/resctrl: Use mbm_update() to push soft RMID counts

Hi Peter,

On 4/21/2023 7:17 AM, Peter Newman wrote:

@@ -806,12 +811,27 @@ void mbm_handle_overflow(struct work_struct *work) r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl; d = container_of(work, struct rdt_domain, mbm_over.work);

• if (rdt_mon_soft_rmid) {

• /*
  

•  * HW RMIDs are permanently assigned to CPUs, so only a per-CPU
  

•  * flush is needed.
  

•  */
  

• on_each_cpu_mask(&d->cpu_mask, mbm_flush_cpu_handler, NULL,
  

• 		 false);
  

• }
• list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {

• mbm_update(r, d, prgrp->mon.rmid);
  

• /*
  

•  * mbm_update() on every RMID would result in excessive IPIs
  

•  * when RMIDs are soft.
  

•  */
  

• if (!rdt_mon_soft_rmid) {
  

• 	mbm_update(r, d, prgrp->mon.rmid);
  

• head = &prgrp->mon.crdtgrp_list;
  

• list_for_each_entry(crgrp, head, mon.crdtgrp_list)
  

• 	mbm_update(r, d, crgrp->mon.rmid);
  

• 	head = &prgrp->mon.crdtgrp_list;
  

• 	list_for_each_entry(crgrp, head, mon.crdtgrp_list)
  

• 		mbm_update(r, d, crgrp->mon.rmid);
  

• }
  

if (is_mba_sc(NULL)) update_mba_bw(prgrp, d);

hmmm ... I think that update_mba_bw() relies on mbm_update() to call mbm_bw_count() to update the data it depends on. Keeping update_mba_bw() while dropping mbm_update() thus seems problematic. AMD does not support the software controller though so it may make things simpler if support for software RMIDs disables support for software controller (in a clear way).

Reinette