Messages in this thread Patch in this message | | | Date | Wed, 14 Dec 2022 17:08:56 +0100 | Subject | [PATCH v2 2/2] x86/resctrl: Avoid redundant counter read in __mon_event_count() | From | Peter Newman <> |
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__mon_event_count() does the per-RMID, per-domain work for user-initiated event count reads and the initialization of new monitor groups.
In the initialization case, after resctrl_arch_reset_rmid() calls __rmid_read() to record an initial count for a new monitor group, it immediately calls resctrl_arch_rmid_read(). This re-read of the hardware counter is unnecessary.
Following return from resctrl_arch_reset_rmid(), just clear the mbm_state and return.
Also, move the mbm_state lookup into the rr->first case, as it's not needed for regular event count reads: the QOS_L3_OCCUP_EVENT_ID case was redundant with the accumulating logic at the end of the function.
Signed-off-by: Peter Newman <peternewman@google.com> --- arch/x86/kernel/cpu/resctrl/monitor.c | 43 ++++++++++++--------------- 1 file changed, 19 insertions(+), 24 deletions(-)
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c index 77538abeb72a..e708df478077 100644 --- a/arch/x86/kernel/cpu/resctrl/monitor.c +++ b/arch/x86/kernel/cpu/resctrl/monitor.c @@ -366,41 +366,36 @@ void free_rmid(u32 rmid) list_add_tail(&entry->list, &rmid_free_lru); } +static struct mbm_state *get_mbm_state(struct rdt_domain *d, u32 rmid, + enum resctrl_event_id evtid) +{ + switch (evtid) { + case QOS_L3_MBM_TOTAL_EVENT_ID: + return &d->mbm_total[rmid]; + case QOS_L3_MBM_LOCAL_EVENT_ID: + return &d->mbm_local[rmid]; + default: + return NULL; + } +} + static int __mon_event_count(u32 rmid, struct rmid_read *rr) { struct mbm_state *m; u64 tval = 0; - if (rr->first) + if (rr->first) { resctrl_arch_reset_rmid(rr->r, rr->d, rmid, rr->evtid); + m = get_mbm_state(rr->d, rmid, rr->evtid); + if (m) + memset(m, 0, sizeof(struct mbm_state)); + return 0; + } rr->err = resctrl_arch_rmid_read(rr->r, rr->d, rmid, rr->evtid, &tval); if (rr->err) return rr->err; - switch (rr->evtid) { - case QOS_L3_OCCUP_EVENT_ID: - rr->val += tval; - return 0; - case QOS_L3_MBM_TOTAL_EVENT_ID: - m = &rr->d->mbm_total[rmid]; - break; - case QOS_L3_MBM_LOCAL_EVENT_ID: - m = &rr->d->mbm_local[rmid]; - break; - default: - /* - * Code would never reach here because an invalid - * event id would fail in resctrl_arch_rmid_read(). - */ - return -EINVAL; - } - - if (rr->first) { - memset(m, 0, sizeof(struct mbm_state)); - return 0; - } - rr->val += tval; return 0; -- 2.39.0.rc1.256.g54fd8350bd-goog
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