git: 3ee596eeee19 - stable/15 - racct: Simplify skipping idle process in the throttling daemon

The branch stable/15 has been updated by olce:

URL: https://cgit.FreeBSD.org/src/commit/?id=3ee596eeee198ede6860cf0c862fb5f8cfc81411

commit 3ee596eeee198ede6860cf0c862fb5f8cfc81411
Author:     Olivier Certner <olce@FreeBSD.org>
AuthorDate: 2025-10-29 15:47:25 +0000
Commit:     Olivier Certner <olce@FreeBSD.org>
CommitDate: 2025-11-06 03:36:28 +0000

    racct: Simplify skipping idle process in the throttling daemon
    
    In racctd(), commit c72188d85a79 ("racct: Improve handling of the pcpu
    resource") added a superfluous test to skip the idle process when
    computing the resource usage and checking for limits, consisting of
    a comparison of the considered process' pointer with that of the process of
    the first CPU's idle thread.  The P_IDLEPROC flag introduced in commit
    33be1632047c ("racct: Fix accounting of CPU time for the system idle
    process") is sufficient and simpler for this purpose.
    
    In the second loop throttling processes based on their %CPU usage, the
    test excluding processes not in PRS_NORMAL was not consistent with that
    of the first loop (which tests for the idle process also).  This had no
    practical consequences except a superfluous call to
    racct_pcpu_available() as the RACCT_PCTCPU counter stays at 0 on the
    idle process (because of the first loop).  Factor out the test in the
    new racct_proc_to_skip() function.
    
    No functional change intended.
    
    Reviewed by:    markj
    MFC after:      3 days
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D53455
    
    (cherry picked from commit 9530c6f082ada9e6d0323f36697ce53997ab2326)
---
 sys/kern/kern_racct.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/sys/kern/kern_racct.c b/sys/kern/kern_racct.c
index 7351e9cb6313..61e92678b54d 100644
--- a/sys/kern/kern_racct.c
+++ b/sys/kern/kern_racct.c
@@ -1236,16 +1236,20 @@ racct_updatepcpu_containers(void)
 	    racct_updatepcpu_post, NULL, NULL);
 }
 
+static bool
+racct_proc_to_skip(const struct proc *p)
+{
+	PROC_LOCK_ASSERT(p, MA_OWNED);
+	return (p->p_state != PRS_NORMAL || (p->p_flag & P_IDLEPROC) != 0);
+}
+
 static void
 racctd(void)
 {
 	struct proc *p;
-	struct proc *idle;
 
 	ASSERT_RACCT_ENABLED();
 
-	idle = STAILQ_FIRST(&cpuhead)->pc_idlethread->td_proc;
-
 	for (;;) {
 		racct_decay();
 
@@ -1253,12 +1257,7 @@ racctd(void)
 
 		FOREACH_PROC_IN_SYSTEM(p) {
 			PROC_LOCK(p);
-			if (p == idle) {
-				PROC_UNLOCK(p);
-				continue;
-			}
-			if (p->p_state != PRS_NORMAL ||
-			    (p->p_flag & P_IDLEPROC) != 0) {
+			if (racct_proc_to_skip(p)) {
 				PROC_UNLOCK(p);
 				continue;
 			}
@@ -1284,7 +1283,7 @@ racctd(void)
 		 */
 		FOREACH_PROC_IN_SYSTEM(p) {
 			PROC_LOCK(p);
-			if (p->p_state != PRS_NORMAL) {
+			if (racct_proc_to_skip(p)) {
 				PROC_UNLOCK(p);
 				continue;
 			}