[PATCH 1/4] os-linux: add initial support for IO priority hints

[Damien Le Moal <dlemoal@kernel.org>]

From: Damien Le Moal <damien.lemoal@opensource.wdc.com>

Add initial support for Linux to allow specifying a hint for any
priority value. With this change, a priority value becomes the
combination of a priority class, a priority level and a hint.
The generic os.h ioprio manipulation macros, as well as the
os-dragonfly.h ioprio manipulation macros  are modified to ignore this
hint.

Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
---
 backend.c         |  5 +++--
 engines/cmdprio.c |  4 ++--
 options.c         |  2 +-
 os/os-dragonfly.h |  4 ++--
 os/os-linux.h     | 17 +++++++++++++----
 os/os.h           |  4 ++--
 6 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/backend.c b/backend.c
index d67a4a07..6641441c 100644
--- a/backend.c
+++ b/backend.c
@@ -1791,12 +1791,13 @@ static void *thread_main(void *data)
 	/* ioprio_set() has to be done before td_io_init() */
 	if (fio_option_is_set(o, ioprio) ||
 	    fio_option_is_set(o, ioprio_class)) {
-		ret = ioprio_set(IOPRIO_WHO_PROCESS, 0, o->ioprio_class, o->ioprio);
+		ret = ioprio_set(IOPRIO_WHO_PROCESS, 0, o->ioprio_class,
+				 o->ioprio, 0);
 		if (ret == -1) {
 			td_verror(td, errno, "ioprio_set");
 			goto err;
 		}
-		td->ioprio = ioprio_value(o->ioprio_class, o->ioprio);
+		td->ioprio = ioprio_value(o->ioprio_class, o->ioprio, 0);
 		td->ts.ioprio = td->ioprio;
 	}
 
diff --git a/engines/cmdprio.c b/engines/cmdprio.c
index 979a81b6..e6ff1fc2 100644
--- a/engines/cmdprio.c
+++ b/engines/cmdprio.c
@@ -342,7 +342,7 @@ static int fio_cmdprio_gen_perc(struct thread_data *td, struct cmdprio *cmdprio)
 		prio = &cmdprio->perc_entry[ddir];
 		prio->perc = options->percentage[ddir];
 		prio->prio = ioprio_value(options->class[ddir],
-					  options->level[ddir]);
+					  options->level[ddir], 0);
 		assign_clat_prio_index(prio, &values[ddir]);
 
 		ret = init_ts_clat_prio(ts, ddir, &values[ddir]);
@@ -400,7 +400,7 @@ static int fio_cmdprio_parse_and_gen_bssplit(struct thread_data *td,
 			goto err;
 
 		implicit_cmdprio = ioprio_value(options->class[ddir],
-						options->level[ddir]);
+						options->level[ddir], 0);
 
 		ret = fio_cmdprio_generate_bsprio_desc(&cmdprio->bsprio_desc[ddir],
 						       &parse_res[ddir],
diff --git a/options.c b/options.c
index a7c4ef6e..c5343d4b 100644
--- a/options.c
+++ b/options.c
@@ -344,7 +344,7 @@ static int parse_cmdprio_bssplit_entry(struct thread_options *o,
 	case 4: /* bs/perc/class/level case */
 		class = min(class, (unsigned int) IOPRIO_MAX_PRIO_CLASS);
 		level = min(level, (unsigned int) IOPRIO_MAX_PRIO);
-		entry->prio = ioprio_value(class, level);
+		entry->prio = ioprio_value(class, level, 0);
 		break;
 	default:
 		log_err("fio: invalid cmdprio_bssplit format\n");
diff --git a/os/os-dragonfly.h b/os/os-dragonfly.h
index bde39101..4ce72539 100644
--- a/os/os-dragonfly.h
+++ b/os/os-dragonfly.h
@@ -171,8 +171,8 @@ static inline int fio_getaffinity(int pid, os_cpu_mask_t *mask)
  * ioprio_set() with 4 arguments, so define fio's ioprio_set() as a macro.
  * Note that there is no idea of class within ioprio_set(2) unlike Linux.
  */
-#define ioprio_value(ioprio_class, ioprio)	(ioprio)
-#define ioprio_set(which, who, ioprio_class, ioprio)	\
+#define ioprio_value(ioprio_class, ioprio, ioprio_hint)	(ioprio)
+#define ioprio_set(which, who, ioprio_class, ioprio, ioprio_hint)	\
 	ioprio_set(which, who, ioprio)
 
 #define ioprio(ioprio)		(ioprio)
diff --git a/os/os-linux.h b/os/os-linux.h
index 2f9f7e79..6f241d09 100644
--- a/os/os-linux.h
+++ b/os/os-linux.h
@@ -125,13 +125,19 @@ enum {
 #define IOPRIO_BITS		16
 #define IOPRIO_CLASS_SHIFT	13
 
+#define IOPRIO_HINT_BITS	10
+#define IOPRIO_HINT_SHIFT	3
+
 #define IOPRIO_MIN_PRIO		0	/* highest priority */
 #define IOPRIO_MAX_PRIO		7	/* lowest priority */
 
 #define IOPRIO_MIN_PRIO_CLASS	0
 #define IOPRIO_MAX_PRIO_CLASS	3
 
-static inline int ioprio_value(int ioprio_class, int ioprio)
+#define IOPRIO_MIN_PRIO_HINT	0
+#define IOPRIO_MAX_PRIO_HINT	((1 << IOPRIO_HINT_BITS) - 1)
+
+static inline int ioprio_value(int ioprio_class, int ioprio, int ioprio_hint)
 {
 	/*
 	 * If no class is set, assume BE
@@ -139,7 +145,9 @@ static inline int ioprio_value(int ioprio_class, int ioprio)
         if (!ioprio_class)
                 ioprio_class = IOPRIO_CLASS_BE;
 
-	return (ioprio_class << IOPRIO_CLASS_SHIFT) | ioprio;
+	return (ioprio_class << IOPRIO_CLASS_SHIFT) |
+		(ioprio_hint << IOPRIO_HINT_SHIFT) |
+		ioprio;
 }
 
 static inline bool ioprio_value_is_class_rt(unsigned int priority)
@@ -147,10 +155,11 @@ static inline bool ioprio_value_is_class_rt(unsigned int priority)
 	return (priority >> IOPRIO_CLASS_SHIFT) == IOPRIO_CLASS_RT;
 }
 
-static inline int ioprio_set(int which, int who, int ioprio_class, int ioprio)
+static inline int ioprio_set(int which, int who, int ioprio_class, int ioprio,
+			     int ioprio_hint)
 {
 	return syscall(__NR_ioprio_set, which, who,
-		       ioprio_value(ioprio_class, ioprio));
+		       ioprio_value(ioprio_class, ioprio, ioprio_hint));
 }
 
 #define ioprio_class(ioprio)	((ioprio) >> IOPRIO_CLASS_SHIFT)
diff --git a/os/os.h b/os/os.h
index 036fc233..2217d5f8 100644
--- a/os/os.h
+++ b/os/os.h
@@ -122,9 +122,9 @@ extern int fio_cpus_split(os_cpu_mask_t *mask, unsigned int cpu);
 #define IOPRIO_MAX_PRIO_CLASS		0
 #endif
 #ifndef FIO_HAVE_IOPRIO
-#define ioprio_value(prioclass, prio)	(0)
+#define ioprio_value(prioclass, prio, priohint)	(0)
 #define ioprio(ioprio)			0
-#define ioprio_set(which, who, prioclass, prio)	(0)
+#define ioprio_set(which, who, prioclass, prio, priohint) (0)
 #define IOPRIO_MIN_PRIO			0
 #define IOPRIO_MAX_PRIO			0
 #endif
-- 
2.41.0