git: c6a65bbee695 - stable/14 - zfs: spa: ZIO_TASKQ_ISSUE: Use symbolic priority

The branch stable/14 has been updated by olce:

URL: https://cgit.FreeBSD.org/src/commit/?id=c6a65bbee6959f50fa9313c63f31ff6e815b48d4

commit c6a65bbee6959f50fa9313c63f31ff6e815b48d4
Author:     Olivier Certner <olce@FreeBSD.org>
AuthorDate: 2024-05-21 14:23:32 +0000
Commit:     Olivier Certner <olce@FreeBSD.org>
CommitDate: 2025-07-28 13:28:21 +0000

    zfs: spa: ZIO_TASKQ_ISSUE: Use symbolic priority
    
    This allows to change the meaning of priority differences in FreeBSD
    without requiring code changes in ZFS.
    
    MFC after:      1 month
    Event:          Kitchener-Waterloo Hackathon 202506
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D45390
    
    (cherry picked from commit fd141584cf89d7d24543ef5be83c6927a5d67ffa)
---
 .../openzfs/include/os/freebsd/spl/sys/proc.h       |  4 +++-
 .../openzfs/include/os/linux/spl/sys/sysmacros.h    |  4 +++-
 sys/contrib/openzfs/include/sys/zfs_context.h       |  4 +++-
 sys/contrib/openzfs/module/zfs/spa.c                | 21 +++------------------
 4 files changed, 12 insertions(+), 21 deletions(-)

diff --git a/sys/contrib/openzfs/include/os/freebsd/spl/sys/proc.h b/sys/contrib/openzfs/include/os/freebsd/spl/sys/proc.h
index 96ba10e5679e..0d02a826870c 100644
--- a/sys/contrib/openzfs/include/os/freebsd/spl/sys/proc.h
+++ b/sys/contrib/openzfs/include/os/freebsd/spl/sys/proc.h
@@ -44,7 +44,9 @@
 #ifdef _KERNEL
 #define	CPU		curcpu
 #define	minclsyspri	PRIBIO
-#define	defclsyspri minclsyspri
+#define	defclsyspri	minclsyspri
+/* Write issue taskq priority. */
+#define	wtqclsyspri	((PVM + PRIBIO) / 2)
 #define	maxclsyspri	PVM
 #define	max_ncpus	(mp_maxid + 1)
 #define	boot_max_ncpus	(mp_maxid + 1)
diff --git a/sys/contrib/openzfs/include/os/linux/spl/sys/sysmacros.h b/sys/contrib/openzfs/include/os/linux/spl/sys/sysmacros.h
index 0e8390736309..96bb01e81541 100644
--- a/sys/contrib/openzfs/include/os/linux/spl/sys/sysmacros.h
+++ b/sys/contrib/openzfs/include/os/linux/spl/sys/sysmacros.h
@@ -91,8 +91,10 @@
  * Treat shim tasks as SCHED_NORMAL tasks
  */
 #define	minclsyspri			(MAX_PRIO-1)
-#define	maxclsyspri			(MAX_RT_PRIO)
 #define	defclsyspri			(DEFAULT_PRIO)
+/* Write issue taskq priority. */
+#define	wtqclsyspri			(MAX_RT_PRIO + 1)
+#define	maxclsyspri			(MAX_RT_PRIO)
 
 #ifndef NICE_TO_PRIO
 #define	NICE_TO_PRIO(nice)		(MAX_RT_PRIO + (nice) + 20)
diff --git a/sys/contrib/openzfs/include/sys/zfs_context.h b/sys/contrib/openzfs/include/sys/zfs_context.h
index 5dedb14c7fb5..accfa3d9da9f 100644
--- a/sys/contrib/openzfs/include/sys/zfs_context.h
+++ b/sys/contrib/openzfs/include/sys/zfs_context.h
@@ -620,8 +620,10 @@ extern void delay(clock_t ticks);
  * Process priorities as defined by setpriority(2) and getpriority(2).
  */
 #define	minclsyspri	19
-#define	maxclsyspri	-20
 #define	defclsyspri	0
+/* Write issue taskq priority. */
+#define	wtqclsyspri	-19
+#define	maxclsyspri	-20
 
 #define	CPU_SEQID	((uintptr_t)pthread_self() & (max_ncpus - 1))
 #define	CPU_SEQID_UNSTABLE	CPU_SEQID
diff --git a/sys/contrib/openzfs/module/zfs/spa.c b/sys/contrib/openzfs/module/zfs/spa.c
index 886867b739f0..b140f55af973 100644
--- a/sys/contrib/openzfs/module/zfs/spa.c
+++ b/sys/contrib/openzfs/module/zfs/spa.c
@@ -1114,29 +1114,14 @@ spa_taskqs_init(spa_t *spa, zio_type_t t, zio_taskq_type_t q)
 			tq = taskq_create_sysdc(name, value, 50, INT_MAX,
 			    spa->spa_proc, zio_taskq_basedc, flags);
 		} else {
-			pri_t pri = maxclsyspri;
 			/*
 			 * The write issue taskq can be extremely CPU
 			 * intensive.  Run it at slightly less important
 			 * priority than the other taskqs.
-			 *
-			 * Under Linux and FreeBSD this means incrementing
-			 * the priority value as opposed to platforms like
-			 * illumos where it should be decremented.
-			 *
-			 * On FreeBSD, if priorities divided by four (RQ_PPQ)
-			 * are equal then a difference between them is
-			 * insignificant.
 			 */
-			if (t == ZIO_TYPE_WRITE && q == ZIO_TASKQ_ISSUE) {
-#if defined(__linux__)
-				pri++;
-#elif defined(__FreeBSD__)
-				pri += 4;
-#else
-#error "unknown OS"
-#endif
-			}
+			const pri_t pri = (t == ZIO_TYPE_WRITE &&
+			    q == ZIO_TASKQ_ISSUE) ?
+			    wtqclsyspri : maxclsyspri;
 			tq = taskq_create_proc(name, value, pri, 50,
 			    INT_MAX, spa->spa_proc, flags);
 		}