The backend.c function switch_ioscheduler() suffers from several
problems:
1) This function only considers the first file of a job. For jobs using
multiple files, the ioscheduler switch will done only for that file.
2) If the job file is a character device, a pipe or a regular file for
which the hosting block device file cannot be determined (e.g. a
remote file), thring to switch the IO scheduler causes a crash as the
file disk_util field is NULL.
Fix both problems by introducing the helper function set_ioscheduler()
and changing switch_ioscheduler() to repeatdly call this helper for all
files of the job, ignoring character device files, pipe files and files
without a hosting device information.
Also update the man page to better explain when the ioscheduler option
applies.
Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
---
Changes form v1:
* Introduce set_ioscheduler() helper
* Change switch_ioscheduler() to operate on all files of a job
* Ignore files that cannot be used to switch scheduler without reporting
an error.
backend.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++---------
fio.1 | 3 ++-
2 files changed, 52 insertions(+), 10 deletions(-)
diff --git a/backend.c b/backend.c
index 52b4ca7e..399c299e 100644
--- a/backend.c
+++ b/backend.c
@@ -1341,22 +1341,19 @@ int init_io_u_buffers(struct thread_data *td)
return 0;
}
+#ifdef FIO_HAVE_IOSCHED_SWITCH
/*
- * This function is Linux specific.
+ * These functions are Linux specific.
* FIO_HAVE_IOSCHED_SWITCH enabled currently means it's Linux.
*/
-static int switch_ioscheduler(struct thread_data *td)
+static int set_ioscheduler(struct thread_data *td, struct fio_file *file)
{
-#ifdef FIO_HAVE_IOSCHED_SWITCH
char tmp[256], tmp2[128], *p;
FILE *f;
int ret;
- if (td_ioengine_flagged(td, FIO_DISKLESSIO))
- return 0;
-
- assert(td->files && td->files[0]);
- sprintf(tmp, "%s/queue/scheduler", td->files[0]->du->sysfs_root);
+ assert(file->du && file->du->sysfs_root);
+ sprintf(tmp, "%s/queue/scheduler", file->du->sysfs_root);
f = fopen(tmp, "r+");
if (!f) {
@@ -1417,11 +1414,55 @@ static int switch_ioscheduler(struct thread_data *td)
fclose(f);
return 0;
+}
+
+static int switch_ioscheduler(struct thread_data *td)
+{
+ struct fio_file *f;
+ unsigned int i;
+ int ret = 0;
+
+ if (td_ioengine_flagged(td, FIO_DISKLESSIO))
+ return 0;
+
+ assert(td->files && td->files[0]);
+
+ for_each_file(td, f, i) {
+
+ /* Only consider regular files and block device files */
+ switch (f->filetype) {
+ case FIO_TYPE_FILE:
+ case FIO_TYPE_BLOCK:
+ /*
+ * Make sure that the device hosting the file could
+ * be determined.
+ */
+ if (!f->du)
+ continue;
+ break;
+ case FIO_TYPE_CHAR:
+ case FIO_TYPE_PIPE:
+ default:
+ continue;
+ }
+
+ ret = set_ioscheduler(td, f);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
#else
+
+static int switch_ioscheduler(struct thread_data *td)
+{
return 0;
-#endif
}
+#endif /* FIO_HAVE_IOSCHED_SWITCH */
+
static bool keep_running(struct thread_data *td)
{
unsigned long long limit;
diff --git a/fio.1 b/fio.1
index f959e00d..8c46d5f0 100644
--- a/fio.1
+++ b/fio.1
@@ -690,7 +690,8 @@ of how that would work.
.TP
.BI ioscheduler \fR=\fPstr
Attempt to switch the device hosting the file to the specified I/O scheduler
-before running.
+before running. If the file is a pipe, a character device file or if device
+hosting the file could not be determined, this option is ignored.
.TP
.BI create_serialize \fR=\fPbool
If true, serialize the file creation for the jobs. This may be handy to
--
2.30.2
