With this change, if the SCHED_RT_PRIO compiler flag has been removed.
Instead multipathd will call getrlimit(RLIMIT_RTPRIO, ...) and look at
the hard limit. It it's 0, multipath will do nothing. Otherwise it will
change its scheduling policy to SCHED_RR and its priority to the hard
limit.
This allows users to change the priority of that multipathd runs with by
adding
LimitRTPRIO=<prio>
to the [Service] section of the multipathd.service unit file. Setting
LimitRTPRIO=0 will make multipathd run as a normal process, while
setting LimitRTPRIO=infinity will make it use the maximum SCHED_RR prio,
which is 99.
To keep the existing behavior, multipathd.service now sets
LimitRTPRIO=infinity
Signed-off-by: Benjamin Marzinski <bmarz...@redhat.com>
---
Notes:
v2: Removed SCHED_RT_PRIO compiler flag at Martin Wilck's suggestion.
Added LimitRTPRIO=infinity to multipathd.service
Makefile.inc | 6 ------
README.md | 3 ---
multipathd/Makefile | 3 ---
multipathd/main.c | 22 +++++++++++++++-------
multipathd/multipathd.service.in | 1 +
5 files changed, 16 insertions(+), 19 deletions(-)
diff --git a/Makefile.inc b/Makefile.inc
index 6d206281..5668e638 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -18,12 +18,6 @@ READLINE :=
# SCSI_DH_MODULES_PRELOAD := scsi_dh_alua scsi_dh_rdac
SCSI_DH_MODULES_PRELOAD :=
-# Multipathd scheduling priority. Set value from 1 to 99 to make multipathd
-# change its scheduling policy to SCHED_RR and its priority to the specified
-# value. set to 0 to stop multipathd from changing the scheduling policy and
-# priority it was started with.
-SCHED_RT_PRIO := 99
-
EXTRAVERSION := $(shell rev=$$(git rev-parse --short=7 HEAD 2>/dev/null); echo
$${rev:+-g$$rev})
# PKG_CONFIG must be read from the environment to enable compilation
diff --git a/README.md b/README.md
index bb41bf0e..d4f35f57 100644
--- a/README.md
+++ b/README.md
@@ -98,9 +98,6 @@ The following variables can be passed to the `make` command
line:
By default, command line editing is disabled.
Note that using libreadline may
[make binary indistributable due to license
incompatibility](https://github.com/opensvc/multipath-tools/issues/36).
- * `SCHED_RT_PRIO={0-99}`: for values {1-99} set the realtime priority
- multipathd will attempt to run with. for value 0, disable multipathd
- changing itself to a realtime process.
* `ENABLE_LIBDMMP=0`: disable building libdmmp
* `ENABLE_DMEVENTS_POLL=0`: disable support for the device-mapper event
polling API. For use with pre-5.0 kernels that don't support dmevent polling
diff --git a/multipathd/Makefile b/multipathd/Makefile
index 7300f07a..997b40cf 100644
--- a/multipathd/Makefile
+++ b/multipathd/Makefile
@@ -57,9 +57,6 @@ $(CLI): $(CLI_OBJS)
cli_handlers.o: cli_handlers.c
$(Q)$(CC) $(CPPFLAGS) $(CFLAGS) -Wno-unused-parameter -c -o $@ $<
-main.o: main.c
- $(Q)$(CC) $(CPPFLAGS) -DSCHED_RT_PRIO=$(SCHED_RT_PRIO) $(CFLAGS) -c -o
$@ $<
-
install:
$(Q)$(INSTALL_PROGRAM) -d $(DESTDIR)$(bindir)
$(Q)$(INSTALL_PROGRAM) -m 755 $(EXEC) $(DESTDIR)$(bindir)
diff --git a/multipathd/main.c b/multipathd/main.c
index 9486a8a3..dd17d5c3 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -3171,14 +3171,23 @@ static void
setscheduler (void)
{
int res;
- static struct sched_param sched_param = {
- .sched_priority = SCHED_RT_PRIO
- };
+ static struct sched_param sched_param;
+ struct rlimit rlim;
+
+ if (getrlimit(RLIMIT_RTPRIO, &rlim) < 0 || rlim.rlim_max == 0)
+ return;
+
+ sched_param.sched_priority = rlim.rlim_max > INT_MAX ? INT_MAX :
+ rlim.rlim_max;
+ res = sched_get_priority_max(SCHED_RR);
+ if (res > 0 && res < sched_param.sched_priority)
+ sched_param.sched_priority = res;
- res = sched_setscheduler (0, SCHED_RR, &sched_param);
+ res = sched_setscheduler(0, SCHED_RR, &sched_param);
if (res == -1)
- condlog(2, "Could not set SCHED_RR at priority 99");
+ condlog(2, "Could not set SCHED_RR at priority %d",
+ sched_param.sched_priority);
return;
}
@@ -3471,8 +3480,7 @@ child (__attribute__((unused)) void *param)
if (!vecs)
goto failed;
- if (SCHED_RT_PRIO)
- setscheduler();
+ setscheduler();
set_oom_adj();
#ifdef FPIN_EVENT_HANDLER
if (conf->marginal_pathgroups == MARGINAL_PATHGROUP_FPIN)
diff --git a/multipathd/multipathd.service.in b/multipathd/multipathd.service.in
index 6d03ff71..18bb367e 100644
--- a/multipathd/multipathd.service.in
+++ b/multipathd/multipathd.service.in
@@ -19,6 +19,7 @@ NotifyAccess=main
ExecStart=/sbin/multipathd -d -s
ExecReload=/sbin/multipathd reconfigure
TasksMax=infinity
+LimitRTPRIO=infinity
[Install]
WantedBy=sysinit.target
--
2.43.0
