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.
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.
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" ?
Regards,
Tvrtko
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