git: 6a69bfc8d548 - stable/13 - hwpmc: Increase thread priority while iterating CPUs.

The branch stable/13 has been updated by mav:

URL: https://cgit.FreeBSD.org/src/commit/?id=6a69bfc8d548f23c5dd3323b9954bc5fae03bf1a

commit 6a69bfc8d548f23c5dd3323b9954bc5fae03bf1a
Author:     Alexander Motin <mav@FreeBSD.org>
AuthorDate: 2022-06-07 02:36:16 +0000
Commit:     Alexander Motin <mav@FreeBSD.org>
CommitDate: 2022-07-04 17:48:10 +0000

    hwpmc: Increase thread priority while iterating CPUs.
    
    This allows to profile already running high-priority threads, that
    otherwise by blocking thread migration to respective CPUs blocked PMC
    management, i.e. profiling could start only when workload completed.
    
    While there, return the thread to its original CPU after iterating
    the list.  Otherwise all threads using PMC end up on the last CPU.
    
    MFC after:      1 month
    
    (cherry picked from commit eff9ee7c0c8e1fe782d6c01a29bb23224b02a847)
---
 sys/dev/hwpmc/hwpmc_logging.c | 21 +++++++++------------
 sys/dev/hwpmc/hwpmc_mod.c     | 17 ++++++++---------
 sys/sys/pmc.h                 |  4 ++++
 3 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/sys/dev/hwpmc/hwpmc_logging.c b/sys/dev/hwpmc/hwpmc_logging.c
index c16adff8c842..8d9015af78e9 100644
--- a/sys/dev/hwpmc/hwpmc_logging.c
+++ b/sys/dev/hwpmc/hwpmc_logging.c
@@ -764,6 +764,7 @@ pmclog_deconfigure_log(struct pmc_owner *po)
 {
 	int error;
 	struct pmclog_buffer *lb;
+	struct pmc_binding pb;
 
 	PMCDBG1(LOG,CFG,1, "de-config po=%p", po);
 
@@ -787,19 +788,16 @@ pmclog_deconfigure_log(struct pmc_owner *po)
 		PMCLOG_RESET_BUFFER_DESCRIPTOR(lb);
 		pmc_plb_rele(lb);
 	}
+	pmc_save_cpu_binding(&pb);
 	for (int i = 0; i < mp_ncpus; i++) {
-		thread_lock(curthread);
-		sched_bind(curthread, i);
-		thread_unlock(curthread);
+		pmc_select_cpu(i);
 		/* return the 'current' buffer to the global pool */
 		if ((lb = po->po_curbuf[curcpu]) != NULL) {
 			PMCLOG_RESET_BUFFER_DESCRIPTOR(lb);
 			pmc_plb_rele(lb);
 		}
 	}
-	thread_lock(curthread);
-	sched_unbind(curthread);
-	thread_unlock(curthread);
+	pmc_restore_cpu_binding(&pb);
 
 	/* drop a reference to the fd */
 	if (po->po_file != NULL) {
@@ -869,18 +867,17 @@ pmclog_schedule_one_cond(struct pmc_owner *po)
 static void
 pmclog_schedule_all(struct pmc_owner *po)
 {
+	struct pmc_binding pb;
+
 	/*
 	 * Schedule the current buffer if any and not empty.
 	 */
+	pmc_save_cpu_binding(&pb);
 	for (int i = 0; i < mp_ncpus; i++) {
-		thread_lock(curthread);
-		sched_bind(curthread, i);
-		thread_unlock(curthread);
+		pmc_select_cpu(i);
 		pmclog_schedule_one_cond(po);
 	}
-	thread_lock(curthread);
-	sched_unbind(curthread);
-	thread_unlock(curthread);
+	pmc_restore_cpu_binding(&pb);
 }
 
 int
diff --git a/sys/dev/hwpmc/hwpmc_mod.c b/sys/dev/hwpmc/hwpmc_mod.c
index e94527041af8..18b8bb1674a3 100644
--- a/sys/dev/hwpmc/hwpmc_mod.c
+++ b/sys/dev/hwpmc/hwpmc_mod.c
@@ -249,9 +249,6 @@ static void	pmc_process_thread_delete(struct thread *td);
 static void	pmc_process_thread_userret(struct thread *td);
 static void	pmc_remove_owner(struct pmc_owner *po);
 static void	pmc_remove_process_descriptor(struct pmc_process *pp);
-static void	pmc_restore_cpu_binding(struct pmc_binding *pb);
-static void	pmc_save_cpu_binding(struct pmc_binding *pb);
-static void	pmc_select_cpu(int cpu);
 static int	pmc_start(struct pmc *pm);
 static int	pmc_stop(struct pmc *pm);
 static int	pmc_syscall_handler(struct thread *td, void *syscall_args);
@@ -739,13 +736,14 @@ pmc_ri_to_classdep(struct pmc_mdep *md, int ri, int *adjri)
  * save the cpu binding of the current kthread
  */
 
-static void
+void
 pmc_save_cpu_binding(struct pmc_binding *pb)
 {
 	PMCDBG0(CPU,BND,2, "save-cpu");
 	thread_lock(curthread);
 	pb->pb_bound = sched_is_bound(curthread);
 	pb->pb_cpu   = curthread->td_oncpu;
+	pb->pb_priority = curthread->td_priority;
 	thread_unlock(curthread);
 	PMCDBG1(CPU,BND,2, "save-cpu cpu=%d", pb->pb_cpu);
 }
@@ -754,16 +752,16 @@ pmc_save_cpu_binding(struct pmc_binding *pb)
  * restore the cpu binding of the current thread
  */
 
-static void
+void
 pmc_restore_cpu_binding(struct pmc_binding *pb)
 {
 	PMCDBG2(CPU,BND,2, "restore-cpu curcpu=%d restore=%d",
 	    curthread->td_oncpu, pb->pb_cpu);
 	thread_lock(curthread);
-	if (pb->pb_bound)
-		sched_bind(curthread, pb->pb_cpu);
-	else
+	sched_bind(curthread, pb->pb_cpu);
+	if (!pb->pb_bound)
 		sched_unbind(curthread);
+	sched_prio(curthread, pb->pb_priority);
 	thread_unlock(curthread);
 	PMCDBG0(CPU,BND,2, "restore-cpu done");
 }
@@ -772,7 +770,7 @@ pmc_restore_cpu_binding(struct pmc_binding *pb)
  * move execution over the specified cpu and bind it there.
  */
 
-static void
+void
 pmc_select_cpu(int cpu)
 {
 	KASSERT(cpu >= 0 && cpu < pmc_cpu_max(),
@@ -784,6 +782,7 @@ pmc_select_cpu(int cpu)
 
 	PMCDBG1(CPU,SEL,2, "select-cpu cpu=%d", cpu);
 	thread_lock(curthread);
+	sched_prio(curthread, PRI_MIN);
 	sched_bind(curthread, cpu);
 	thread_unlock(curthread);
 
diff --git a/sys/sys/pmc.h b/sys/sys/pmc.h
index 662c3f095304..91ce5d2bd71f 100644
--- a/sys/sys/pmc.h
+++ b/sys/sys/pmc.h
@@ -997,6 +997,7 @@ struct pmc_cpu {
 struct pmc_binding {
 	int	pb_bound;	/* is bound? */
 	int	pb_cpu;		/* if so, to which CPU */
+	u_char	pb_priority;	/* Thread active priority. */
 };
 
 struct pmc_mdep;
@@ -1225,6 +1226,9 @@ int	pmc_save_kernel_callchain(uintptr_t *_cc, int _maxsamples,
     struct trapframe *_tf);
 int	pmc_save_user_callchain(uintptr_t *_cc, int _maxsamples,
     struct trapframe *_tf);
+void	pmc_restore_cpu_binding(struct pmc_binding *pb);
+void	pmc_save_cpu_binding(struct pmc_binding *pb);
+void	pmc_select_cpu(int cpu);
 struct pmc_mdep *pmc_mdep_alloc(int nclasses);
 void pmc_mdep_free(struct pmc_mdep *md);
 uint64_t pmc_rdtsc(void);