Commit-ID: b7dbead4e06a6b9a7f74a7bd65e9e2f0770158b5
Gitweb: http://git.kernel.org/tip/b7dbead4e06a6b9a7f74a7bd65e9e2f0770158b5
Author: Prasad Joshi <prasadjoshi124@xxxxxxxxx>
AuthorDate: Fri, 10 Jun 2011 11:35:20 +0100
Committer: Pekka Enberg <penberg@xxxxxxxxxx>
CommitDate: Wed, 15 Jun 2011 16:59:37 +0300
kvm tools: Add IO delay option
Add a command line debug option to add a fix amount of delay in read and
write operation.
>From Ingo "the delays are *constant* [make sure you use a high-res timers
kernel], so they do not result in nearly as much measurement noise as real
block IO does.
[...]
This way you are basically 'emulating' a real disk drive but you will
emulate uniform latencies, which makes measurements a lot more
reliable - while still relevant to the end result."
Suggested-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Prasad Joshi <prasadjoshi124@xxxxxxxxx>
Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxx>
---
tools/kvm/disk/core.c | 8 ++++++++
tools/kvm/include/kvm/util.h | 7 +++++++
tools/kvm/kvm-run.c | 3 +++
3 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/tools/kvm/disk/core.c b/tools/kvm/disk/core.c
index f2b482a..965bbe5 100644
--- a/tools/kvm/disk/core.c
+++ b/tools/kvm/disk/core.c
@@ -1,6 +1,8 @@
#include "kvm/disk-image.h"
#include "kvm/qcow.h"
+int debug_iodelay;
+
struct disk_image *disk_image__new(int fd, u64 size, struct disk_image_operations *ops, int use_mmap)
{
struct disk_image *disk;
@@ -132,6 +134,9 @@ ssize_t disk_image__read(struct disk_image *disk, u64 sector, const struct iovec
ssize_t total = 0;
ssize_t nr;
+ if (debug_iodelay)
+ msleep(debug_iodelay);
+
if (disk->ops->read_sector_iov) {
/*
* Try mulitple buffer based operation first
@@ -170,6 +175,9 @@ ssize_t disk_image__write(struct disk_image *disk, u64 sector, const struct iove
ssize_t total = 0;
ssize_t nr;
+ if (debug_iodelay)
+ msleep(debug_iodelay);
+
if (disk->ops->write_sector_iov) {
/*
* Try writev based operation first
diff --git a/tools/kvm/include/kvm/util.h b/tools/kvm/include/kvm/util.h
index a9425cc..dc2e0b9 100644
--- a/tools/kvm/include/kvm/util.h
+++ b/tools/kvm/include/kvm/util.h
@@ -68,4 +68,11 @@ static inline const char *skip_prefix(const char *str, const char *prefix)
return strncmp(str, prefix, len) ? NULL : str + len;
}
+#define MSECS_TO_USECS(s) ((s) * 1000)
+
+/* Millisecond sleep */
+static inline void msleep(unsigned int msecs)
+{
+ usleep(MSECS_TO_USECS(msecs));
+}
#endif /* KVM__UTIL_H */
diff --git a/tools/kvm/kvm-run.c b/tools/kvm/kvm-run.c
index 201019a..f121a2b 100644
--- a/tools/kvm/kvm-run.c
+++ b/tools/kvm/kvm-run.c
@@ -76,6 +76,7 @@ static bool vnc;
static bool sdl;
extern bool ioport_debug;
extern int active_console;
+extern int debug_iodelay;
bool do_debug_print = false;
@@ -151,6 +152,8 @@ static const struct option options[] = {
"Enable single stepping"),
OPT_BOOLEAN('\0', "debug-ioport-debug", &ioport_debug,
"Enable ioport debugging"),
+ OPT_INTEGER('\0', "debug_iodelay", &debug_iodelay,
+ "Delay IO by millisecond"),
OPT_END()
};
--
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