On 7/18/2016 6:36 PM, Tvrtko Ursulin wrote:
On 18/07/16 13:19, Goel, Akash wrote:
On 7/18/2016 3:36 PM, Tvrtko Ursulin wrote:
On 15/07/16 16:36, Goel, Akash wrote:
On 7/15/2016 4:45 PM, Tvrtko Ursulin wrote:
On 10/07/16 14:41, akash.goel@xxxxxxxxx wrote:
From: Akash Goel <akash.goel@xxxxxxxxx>
On recieving the log buffer flush interrupt from GuC firmware, Driver
stores the snapshot of the log buffer in a local buffer, from which
Userspace can pull the logs. By default Driver store, up to, 4
snapshots
of the log buffer in a local buffer (managed by relay).
Added a new module (read only) param, 'guc_log_size', through which
User
can specify the number of snapshots of log buffer to be stored in
local
buffer. This can be used to ensure capturing of all boot time logs
even
with high verbosity level.
v2: Rename module param to more apt name 'guc_log_buffer_nr'.
(Nikula)
Suggested-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Akash Goel <akash.goel@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_guc_submission.c | 3 +--
drivers/gpu/drm/i915/i915_params.c | 5 +++++
drivers/gpu/drm/i915/i915_params.h | 1 +
3 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c
b/drivers/gpu/drm/i915/i915_guc_submission.c
index 2e3b723..009d7c0 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -1046,8 +1046,7 @@ static int guc_create_log_relay_file(struct
intel_guc *guc)
/* Keep the size of sub buffers same as shared log buffer */
subbuf_size = guc->log.obj->base.size;
- /* TODO: Decide based on the User's input */
- n_subbufs = 4;
+ n_subbufs = i915.guc_log_buffer_nr;
guc_log_relay_chan = relay_open("guc_log", log_dir,
subbuf_size, n_subbufs, &relay_callbacks, dev);
diff --git a/drivers/gpu/drm/i915/i915_params.c
b/drivers/gpu/drm/i915/i915_params.c
index 8b13bfa..d30c972 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -57,6 +57,7 @@ struct i915_params i915 __read_mostly = {
.enable_guc_loading = -1,
.enable_guc_submission = -1,
.guc_log_level = -1,
+ .guc_log_buffer_nr = 4,
.enable_dp_mst = true,
.inject_load_failure = 0,
.enable_dpcd_backlight = false,
@@ -214,6 +215,10 @@ module_param_named(guc_log_level,
i915.guc_log_level, int, 0400);
MODULE_PARM_DESC(guc_log_level,
"GuC firmware logging level (-1:disabled (default),
0-3:enabled)");
+module_param_named(guc_log_buffer_nr, i915.guc_log_buffer_nr, int,
0400);
+MODULE_PARM_DESC(guc_log_buffer_nr,
+ "Number of sub buffers to store GuC firmware logs (default:
4)");
+
module_param_named_unsafe(enable_dp_mst, i915.enable_dp_mst, bool,
0600);
MODULE_PARM_DESC(enable_dp_mst,
"Enable multi-stream transport (MST) for new DisplayPort sinks.
(default: true)");
diff --git a/drivers/gpu/drm/i915/i915_params.h
b/drivers/gpu/drm/i915/i915_params.h
index 0ad020b..14ca855 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -48,6 +48,7 @@ struct i915_params {
int enable_guc_loading;
int enable_guc_submission;
int guc_log_level;
+ int guc_log_buffer_nr;
int use_mmio_flip;
int mmio_debug;
int edp_vswing;
I did not figure out after a quick read of
Documentation/filesystems/relay.txt whether we really need this to be
configurable?
If I got it right number of sub-buffers here only has a relation to
the
userspace relay consumer latency. If the userspace is responsive
should
just two be enough? Or the existing default of four was shown in
practice that it is better and good enough?
Yes one of the use of this module parameter is to give User some leeway
i.e. more time to collect logs from the relay buffer. User may not be
always able to match the rate at which logs are being produced from the
GuC side.
2 could be too less.
Even 4, when running a benchmark, was proving less and not able to
match
the Driver rate (this might change after some optimization is done from
User space side also, like splice).
Okay, it makes sense for it to be bigger than four by default then,
correct?
The other use is to ensure capturing of all boot time logs, even with
maximum verbosity level. The default number of sub buffers may not
always be sufficient to store all the logs from boot, by the time User
is ready to capture the logs.
Saw about 8 flush interrupts coming from GuC during the boot.
How important it is for a default value to capture all activity since
boot?
I think we need to keep in mind here that amount of that activity may be
a lot different with different setups so it might not be that
interesting after all.
Someone will log in via a display manager, which may generate a widely
differing amount of GPU activity, until they start the logger. Someone
else on the other hand might be booting to vt only, starting the logger,
and only then starting the graphical UI.
Agree, that's why its useful to have a provision for altering the
size of buffer.
Maybe. :) I have to be critical here since bar for adding new params is
high. If we can have a default value which works for everyone it would
be better. Of course if the size is not too big then.
Sorry that's what I unable to say right now, a default value which can
cater to most workloads and is not too high also.
That's why I asked how important is being able to capture everything
since boot. Is that a real use case and how important it is?
It might be needed in certain cases, probably while enabling new platforms.
I am just not sure this is a useful module parameter without some more
data.
Even if it is needed, as minimum I think the name should reflect
this is
about the relay side of things and not the GuC log buffer itself. So
something like i915.guc_relay_log_subbuf_nr or something.
Fine will use this name.
With the matching description of course.
Is the current description not apt ?
"Number of sub buffers to store GuC firmware logs (default: 4)");"
My thinking is, what will this parameter mostly be used for? I think the
default needs to be such that a reasonable implementation of an
userspace logger can cope with the flush rate. I am not so sure that
capturing boot time activity by default is that critical.
The default value can be kept as 2 also, as you suggested .
But you said even 4 was not enough to ensure userspace logger can keep up?
Yes 4 doesn't seems to be enough for runtime logging with certain
benchmarks at least.
Actually since logging would generally be disabled by default, so if
User has a need to capture all boot time logs, it will have to anyways
enable the logging (i915.guc_log_level >= 0) first and so at that time
it can also chose a suitable i915.guc_relay_log_subbuf_nr value.
The logging stats from the output of 'i915_guc_info' debugfs can be used
to know how many sub buffers will be required to capture all boot time
logs.
Similarly for run time logging, User can tune the value according to the
benchmarks, as for some of the benchmarks the amount of logs
generated is comparatively much more.
I don't see why would they need to tune this depending on the benchmark.
My assumption is they start the logger and then start the benchmark. The
only important thing it that number of sub-buffers is large enough for
userspace to cope with the flush rate.
Yes if a reasonable default value can be figured out, which can cover
most workloads, then no need of this parameter.
Assuming you find a value to satisfy the above, what are the scenarios
someone will need/want to tweak it and what description of the tunable
would help them understand what it is for?
Should we say, in the description, something like "increase this if you
want to capture all boot time activity until you can start the logging"
and/or "increase this if experiencing logging drops" ?
Yes this would be much better description, in fact I myself wanted to
use a similar description initially, but for brevity sake did not use it
(though sorry could have captured that in commit message).
Will use this only now.
Cool.
Regards,
Tvrtko
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