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Commit ba0f26d8 authored by Vikas Shivappa's avatar Vikas Shivappa Committed by Thomas Gleixner
Browse files

x86/intel_rdt/mba_sc: Prepare for feedback loop 



This is a preparatory patch for the mba feedback loop. Add support to
measure the "bandwidth in MBps" and the "delta bandwidth". Measure it by
reading the MBM IA32_QM_CTR MSRs and calculating the amount of "bytes"
moved. There is no user space interface for this and will only be used by
the feedback loop patch.

Signed-off-by: default avatarVikas Shivappa <vikas.shivappa@linux.intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: ravi.v.shankar@intel.com
Cc: tony.luck@intel.com
Cc: fenghua.yu@intel.com
Cc: vikas.shivappa@intel.com
Cc: ak@linux.intel.com
Cc: hpa@zytor.com
Link: https://lkml.kernel.org/r/1524263781-14267-6-git-send-email-vikas.shivappa@linux.intel.com
parent 8205a078

arch/x86/kernel/cpu/intel_rdt.h

+10 −0
Original line number Diff line number Diff line
@@ -180,10 +180,20 @@ struct rftype { 
 * struct mbm_state - status for each MBM counter in each domain

 * @chunks:	Total data moved (multiply by rdt_group.mon_scale to get bytes)

 * @prev_msr	Value of IA32_QM_CTR for this RMID last time we read it

 * @chunks_bw	Total local data moved. Used for bandwidth calculation

 * @prev_bw_msr:Value of previous IA32_QM_CTR for bandwidth counting

 * @prev_bw	The most recent bandwidth in MBps

 * @delta_bw	Difference between the current and previous bandwidth

 * @delta_comp	Indicates whether to compute the delta_bw

 */

struct mbm_state {

	u64	chunks;

	u64	prev_msr;

	u64	chunks_bw;

	u64	prev_bw_msr;

	u32	prev_bw;

	u32	delta_bw;

	bool	delta_comp;

};



/**

arch/x86/kernel/cpu/intel_rdt_monitor.c

+38 −6
Original line number Diff line number Diff line
@@ -225,10 +225,18 @@ void free_rmid(u32 rmid) 
		list_add_tail(&entry->list, &rmid_free_lru);

}



static u64 mbm_overflow_count(u64 prev_msr, u64 cur_msr)

{

	u64 shift = 64 - MBM_CNTR_WIDTH, chunks;



	chunks = (cur_msr << shift) - (prev_msr << shift);

	return chunks >>= shift;

}



static int __mon_event_count(u32 rmid, struct rmid_read *rr)

{

	u64 chunks, shift, tval;

	struct mbm_state *m;

	u64 chunks, tval;



	tval = __rmid_read(rmid, rr->evtid);

	if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL)) {
@@ -254,14 +262,12 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr) 
	}



	if (rr->first) {

		m->prev_msr = tval;

		m->chunks = 0;

		memset(m, 0, sizeof(struct mbm_state));

		m->prev_bw_msr = m->prev_msr = tval;

		return 0;

	}



	shift = 64 - MBM_CNTR_WIDTH;

	chunks = (tval << shift) - (m->prev_msr << shift);

	chunks >>= shift;

	chunks = mbm_overflow_count(m->prev_msr, tval);

	m->chunks += chunks;

	m->prev_msr = tval;
@@ -269,6 +275,32 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr) 
	return 0;

}



/*

 * Supporting function to calculate the memory bandwidth

 * and delta bandwidth in MBps.

 */

static void mbm_bw_count(u32 rmid, struct rmid_read *rr)

{

	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3];

	struct mbm_state *m = &rr->d->mbm_local[rmid];

	u64 tval, cur_bw, chunks;



	tval = __rmid_read(rmid, rr->evtid);

	if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL))

		return;



	chunks = mbm_overflow_count(m->prev_bw_msr, tval);

	m->chunks_bw += chunks;

	m->chunks = m->chunks_bw;

	cur_bw = (chunks * r->mon_scale) >> 20;



	if (m->delta_comp)

		m->delta_bw = abs(cur_bw - m->prev_bw);

	m->delta_comp = false;

	m->prev_bw = cur_bw;

	m->prev_bw_msr = tval;

}



/*

 * This is called via IPI to read the CQM/MBM counters

 * on a domain.