Re: [PATCH v3 19/27] powerpc/powernv/pmem: Add an IOCTL to report controller statistics

["Alastair D'Silva" <alastair@au1.ibm.com>]

On Wed, 2020-03-04 at 10:25 +0100, Frederic Barrat wrote:
> 
> Le 21/02/2020 à 04:27, Alastair D'Silva a écrit :
> > From: Alastair D'Silva <alastair@d-silva.org>
> > 
> > The controller can report a number of statistics that are useful
> > in evaluating the performance and reliability of the card.
> > 
> > This patch exposes this information via an IOCTL.
> > 
> > Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
> > ---
> >   arch/powerpc/platforms/powernv/pmem/ocxl.c | 185
> > +++++++++++++++++++++
> >   include/uapi/nvdimm/ocxl-pmem.h            |  17 ++
> >   2 files changed, 202 insertions(+)
> > 
> > diff --git a/arch/powerpc/platforms/powernv/pmem/ocxl.c
> > b/arch/powerpc/platforms/powernv/pmem/ocxl.c
> > index 2cabafe1fc58..009d4fd29e7d 100644
> > --- a/arch/powerpc/platforms/powernv/pmem/ocxl.c
> > +++ b/arch/powerpc/platforms/powernv/pmem/ocxl.c
> > @@ -758,6 +758,186 @@ static int
> > ioctl_controller_dump_complete(struct ocxlpmem *ocxlpmem)
> >   				    GLOBAL_MMIO_HCI_CONTROLLER_DUMP_COL
> > LECTED);
> >   }
> >   
> > +/**
> > + * controller_stats_header_parse() - Parse the first 64 bits of
> > the controller stats admin command response
> > + * @ocxlpmem: the device metadata
> > + * @length: out, returns the number of bytes in the response
> > (excluding the 64 bit header)
> > + */
> > +static int controller_stats_header_parse(struct ocxlpmem
> > *ocxlpmem,
> > +	u32 *length)
> > +{
> > +	int rc;
> > +	u64 val;
> > +
> 
> unexpected empty line
> 

Ok

> 
> > +	u16 data_identifier;
> > +	u32 data_length;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset,
> > +				     OCXL_LITTLE_ENDIAN, &val);
> > +	if (rc)
> > +		return rc;
> > +
> > +	data_identifier = val >> 48;
> > +	data_length = val & 0xFFFFFFFF;
> > +
> > +	if (data_identifier != 0x4353) { // 'CS'
> > +		dev_err(&ocxlpmem->dev,
> > +			"Bad data identifier for controller stats,
> > expected 'CS', got '%-.*s'\n",
> > +			2, (char *)&data_identifier);
> 
> 
> Wow, I'm clueless what that string format looks like :-)
> 2 arguments? Did you check the kernel string formatter does what you
> want?
> You may consider unifying the format though, the error log patch uses
> a 
> simpler (better?) format for a similar message.
> 

Sorry, force of habit from my old job where we dealt with a lot of
variable length, non-NULL terminated buffers. FYI - it takes the string
length from the first argument.

I'll change it to a fixed length string like the others :)

> 
> 
> > +		return -EINVAL;
> > +	}
> > +
> > +	*length = data_length;
> > +	return 0;
> > +}
> > +
> > +static int ioctl_controller_stats(struct ocxlpmem *ocxlpmem,
> > +				  struct
> > ioctl_ocxl_pmem_controller_stats __user *uarg)
> > +{
> > +	struct ioctl_ocxl_pmem_controller_stats args;
> > +	u32 length;
> > +	int rc;
> > +	u64 val;
> > +
> > +	memset(&args, '\0', sizeof(args));
> > +
> > +	mutex_lock(&ocxlpmem->admin_command.lock);
> > +
> > +	rc = admin_command_request(ocxlpmem,
> > ADMIN_COMMAND_CONTROLLER_STATS);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = ocxl_global_mmio_write64(ocxlpmem->ocxl_afu,
> > +				      ocxlpmem-
> > >admin_command.request_offset + 0x08,
> > +				      OCXL_LITTLE_ENDIAN, 0);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = admin_command_execute(ocxlpmem);
> > +	if (rc)
> > +		goto out;
> > +
> > +
> > +	rc = admin_command_complete_timeout(ocxlpmem,
> > +					    ADMIN_COMMAND_CONTROLLER_ST
> > ATS);
> > +	if (rc < 0) {
> > +		dev_warn(&ocxlpmem->dev, "Controller stats timed
> > out\n");
> > +		goto out;
> > +	}
> > +
> > +	rc = admin_response(ocxlpmem);
> > +	if (rc < 0)
> > +		goto out;
> > +	if (rc != STATUS_SUCCESS) {
> > +		warn_status(ocxlpmem,
> > +			    "Unexpected status from controller stats",
> > rc);
> > +		goto out;
> > +	}
> 
> All those ioctls commands follow the same pattern:
> 1. admin_command_request()
> 2. optionnaly, set some mmio registers specific to the command
> 3. admin_command_execute()
> 4. admin_command_complete_timeout()
> 5. admin_response()
> 
> By swapping 1 and 2, we could then factorize steps 1, 3, 4 and 5 in
> a 
> function and simplify/shorten the code each time a command is called.
> 
> Regarding step 2 (and that's true for all similar patches), a
> comment 
> about what the mmio tuning does would help and avoid looking up the 
> spec. Looking up the spec during the review is expected, but it will 
> ease reading the code 6 months from now.
> 
> 

I'll rework this and add a wrapper in the Admin Commands patch.

> 
> > +
> > +	rc = controller_stats_header_parse(ocxlpmem, &length);
> > +	if (rc)
> > +		goto out;
> > +
> > +	if (length != 0x140)
> > +		warn_status(ocxlpmem,
> > +			    "Unexpected length for controller stats
> > data, expected 0x140, got 0x%x",
> > +			    length);
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x08,
> > +				     OCXL_LITTLE_ENDIAN, &val);
> > +	if (rc)
> > +		goto out;
> > +
> > +	args.reset_count = val >> 32;
> > +	args.reset_uptime = val & 0xFFFFFFFF;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x10,
> > +				     OCXL_LITTLE_ENDIAN, &val);
> > +	if (rc)
> > +		goto out;
> > +
> > +	args.power_on_uptime = val >> 32;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x40 + 0x08,
>  > +				     OCXL_LITTLE_ENDIAN,
> &args.host_load_count);
> 
> 
> Those offsets are hard to understand, even with the spec next to me.
> And 
> it seems that we could harden things a bit:
> each block as a "statistics parameter ID" and the length of the data
> for 
> that block. We should check that and make sure we're reading what we
> expect.
> For example, from the spec I'm looking (110d), I would expect the
> host 
> load count to be at offset 0x10. It's entirely possible I'm
> misreading 
> it though.
> 

I'll rework this too.

> 
> 
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x40 + 0x10,
> > +				     OCXL_LITTLE_ENDIAN,
> > &args.host_store_count);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x40 + 0x18,
> > +				     OCXL_LITTLE_ENDIAN,
> > &args.media_read_count);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x40 + 0x20,
> > +				     OCXL_LITTLE_ENDIAN,
> > &args.media_write_count);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x40 + 0x28,
> > +				     OCXL_LITTLE_ENDIAN,
> > &args.cache_hit_count);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x40 + 0x30,
> > +				     OCXL_LITTLE_ENDIAN,
> > &args.cache_miss_count);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x40 + 0x38,
> > +				     OCXL_LITTLE_ENDIAN,
> > &args.media_read_latency);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x40 + 0x40,
> > +				     OCXL_LITTLE_ENDIAN,
> > &args.media_write_latency);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x40 + 0x48,
> > +				     OCXL_LITTLE_ENDIAN,
> > &args.cache_read_latency);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +				     ocxlpmem-
> > >admin_command.data_offset + 0x08 + 0x40 + 0x50,
> > +				     OCXL_LITTLE_ENDIAN,
> > &args.cache_write_latency);
> > +	if (rc)
> > +		goto out;
> > +
> > +	if (copy_to_user(uarg, &args, sizeof(args))) {
> > +		rc = -EFAULT;
> > +		goto out;
> > +	}
> > +
> > +	rc = admin_response_handled(ocxlpmem);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = 0;
> > +	goto out;
> 
> That may be more of a personal habit, but that final goto disrupts
> the 
> "good case" flow. And I think it's pretty unusual within the kernel.
> 

Ok

> 
> > +
> > +out:
> > +	mutex_unlock(&ocxlpmem->admin_command.lock);
> > +	return rc;
> > +}
> > +
> >   static long file_ioctl(struct file *file, unsigned int cmd,
> > unsigned long args)
> >   {
> >   	struct ocxlpmem *ocxlpmem = file->private_data;
> > @@ -781,6 +961,11 @@ static long file_ioctl(struct file *file,
> > unsigned int cmd, unsigned long args)
> >   	case IOCTL_OCXL_PMEM_CONTROLLER_DUMP_COMPLETE:
> >   		rc = ioctl_controller_dump_complete(ocxlpmem);
> >   		break;
> > +
> > +	case IOCTL_OCXL_PMEM_CONTROLLER_STATS:
> > +		rc = ioctl_controller_stats(ocxlpmem,
> > +					    (struct
> > ioctl_ocxl_pmem_controller_stats __user *)args);
> > +		break;
> >   	}
> >   
> >   	return rc;
> > diff --git a/include/uapi/nvdimm/ocxl-pmem.h
> > b/include/uapi/nvdimm/ocxl-pmem.h
> > index d4d8512d03f7..add223aa2fdb 100644
> > --- a/include/uapi/nvdimm/ocxl-pmem.h
> > +++ b/include/uapi/nvdimm/ocxl-pmem.h
> > @@ -50,6 +50,22 @@ struct ioctl_ocxl_pmem_controller_dump_data {
> >   	__u64 reserved[8];
> >   };
> >   
> > +struct ioctl_ocxl_pmem_controller_stats {
> > +	__u32 reset_count;
> > +	__u32 reset_uptime; /* seconds */
> > +	__u32 power_on_uptime; /* seconds */
> 
> Same as before, we're going to have some padding here.
> 
>    Fred
> 
Ok

> 
> > +	__u64 host_load_count;
> > +	__u64 host_store_count;
> > +	__u64 media_read_count;
> > +	__u64 media_write_count;
> > +	__u64 cache_hit_count;
> > +	__u64 cache_miss_count;
> > +	__u64 media_read_latency; /* nanoseconds */
> > +	__u64 media_write_latency; /* nanoseconds */
> > +	__u64 cache_read_latency; /* nanoseconds */
> > +	__u64 cache_write_latency; /* nanoseconds */
> > +};
> > +
> >   /* ioctl numbers */
> >   #define OCXL_PMEM_MAGIC 0x5C
> >   /* SCM devices */
> > @@ -57,5 +73,6 @@ struct ioctl_ocxl_pmem_controller_dump_data {
> >   #define IOCTL_OCXL_PMEM_CONTROLLER_DUMP			_IO(OCX
> > L_PMEM_MAGIC, 0x02)
> >   #define IOCTL_OCXL_PMEM_CONTROLLER_DUMP_DATA		_IOWR(O
> > CXL_PMEM_MAGIC, 0x03, struct ioctl_ocxl_pmem_controller_dump_data)
> >   #define IOCTL_OCXL_PMEM_CONTROLLER_DUMP_COMPLETE	_IO(OCXL_PMEM_M
> > AGIC, 0x04)
> > +#define IOCTL_OCXL_PMEM_CONTROLLER_STATS		_IO(OCXL_PMEM_M
> > AGIC, 0x05)
> >   
> >   #endif /* _UAPI_OCXL_SCM_H */
> > 
-- 
Alastair D'Silva
Open Source Developer
Linux Technology Centre, IBM Australia
mob: 0423 762 819