Hello,
It looks like powertop requires a kernel patch to display VFS ops/sec.
The last patch was for kernel v3.3.0. The patch needs to be updated,
otherwise powertop always displays 0 VFS ops/sec.
Considering changes starting with kernel v3.9, the kernel side patch
would look like as below. I have tested it with powertop and
linux-linaro-tracking branch (v3.14.0) and with this patch powertop
displays and updates VFS ops/sec properly.
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5584bea..c6a9832 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1141,6 +1141,9 @@ void __mark_inode_dirty(struct inode *inode, int flags)
if ((inode->i_state & flags) == flags)
return;
+ if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES))
+ trace_writeback_inode_dirty(inode, flags);
+
if (unlikely(block_dump > 1))
block_dump___mark_inode_dirty(inode);
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 464ea82..7956d8f 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -101,6 +101,35 @@ DEFINE_EVENT(writeback_dirty_inode_template,
writeback_dirty_inode,
TP_ARGS(inode, flags)
);
+/*
+ * Tracepoint for dirtying an inode; used by PowerTOP
+ */
+TRACE_EVENT(writeback_inode_dirty,
+
+ TP_PROTO(struct inode *inode, int flags),
+
+ TP_ARGS(inode, flags),
+
+ TP_STRUCT__entry(
+ __field( __kernel_dev_t, dev )
+ __field( ino_t, ino )
+ __field( u32, flags )
+ ),
+
+ TP_fast_assign(
+ __entry->dev = inode->i_sb->s_dev;
+ __entry->ino = inode->i_ino;
+ __entry->flags = flags;
+ ),
+
+ TP_printk("dev %d:%d ino %lu flags %d %s", MAJOR(__entry->dev),
+ MINOR(__entry->dev),
+ (unsigned long) __entry->ino,
+ __entry->flags,
+ show_inode_state(__entry->flags)
+ )
+);
+
DECLARE_EVENT_CLASS(writeback_write_inode_template,
TP_PROTO(struct inode *inode, struct writeback_control *wbc),
However, there is an alternative thought.
Starting with kernel v3.9, kernel provides a built in trace event
called - "writeback_dirty_inode" -
DEFINE_EVENT(writeback_dirty_inode_template, writeback_dirty_inode,
TP_PROTO(struct inode *inode, int flags),
TP_ARGS(inode, flags)
);
But since the event powertop expects is "writeback_inode_dirty" and
the names and output format don't match,
to take advantage of the built-in kernel trace event, the below two
patches together make it work.
powertop side patch is necessary to match the TRACE_EVENT name. Also,
checking for dev > 0 is not necessary,
since now there is name instead of device major and minor number in
kernel trace.
kernel side patch is necessary to account for DIRTY_PAGES.
powertop side patch -
diff --git a/src/process/do_process.cpp b/src/process/do_process.cpp
index ba164eb..2e2cbea 100644
--- a/src/process/do_process.cpp
+++ b/src/process/do_process.cpp
@@ -625,21 +625,14 @@ void
perf_process_bundle::handle_trace_point(void *trace, int cpu, uint64_t
time
consumer->gpu_ops++;
}
}
- else if (strcmp(event->name, "writeback_inode_dirty") == 0) {
- static uint64_t prev_time;
+ else if (strcmp(event->name, "writeback_dirty_inode") == 0) {
+ static uint64_t prev_time = 0;
class power_consumer *consumer = NULL;
- int dev;
consumer = current_consumer(cpu);
- ret = pevent_get_field_val(NULL, event, "dev", &rec, &val, 0);
- if (ret < 0)
-
- return;
- dev = (int)val;
-
if (consumer && strcmp(consumer->name(),
- "process")==0 && dev > 0) {
+ "process")==0) {
consumer->disk_hits++;
@@ -674,7 +667,7 @@ void start_process_measurement(void)
perf_events->add_event("workqueue:workqueue_execute_end");
perf_events->add_event("i915:i915_gem_ring_dispatch");
perf_events->add_event("i915:i915_gem_request_submit");
- perf_events->add_event("writeback:writeback_inode_dirty");
+ perf_events->add_event("writeback:writeback_dirty_inode");
}
first_stamp = ~0ULL;
kernel side patch -
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5584bea..c2ab700 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1141,6 +1141,9 @@ void __mark_inode_dirty(struct inode *inode, int flags)
if ((inode->i_state & flags) == flags)
return;
+ if (flags & I_DIRTY_PAGES)
+ trace_writeback_dirty_inode(inode, flags);
+
if (unlikely(block_dump > 1))
block_dump___mark_inode_dirty(inode);
I have tested both solutions and both displays and updates VFS
ops/sec. However, since second solution changes powertop,
that means powertop won't work with pre v3.9 kernel.
Any comment or thought on this?
--
Thanks,
-Meraj
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