From f4cdf7ca9a1fdcca413157df19753f388a5a224e Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 19 Aug 2026 10:09:22 -0700 Subject: Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media Pull media updates from Mauro Carvalho Chehab: - v4l2-core: added ISP statistics support and per-block validation - v4l2-core: Allow unknown HDR10 white point and luminance - New camera sensors: Sony IMX678 and IMX471m, Himax HM1092 IR sensor - New codec: Milos: VPU v2.0 codec support - isp driver: gained support for Dreamchip RPPX1 ISP framework - vsp1 driver: gained support for RZ/T2H and RZ/N2H - Novalake driver: gained CVS support for new NVL hardware - dvb-core: fix feed leak on failed DMX_ADD_PID - several driver fixes, cleanups and minor improvements * tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (308 commits) media: ipu-bridge: check all DMI entries when overriding sensor rotation media: v4l2-async: avoid deleting unlinked ASC entry on link error media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement media: intel/ipu6: fix async notifier cleanup leak on parse error media: staging/ipu7: fix async notifier UAF on probe error path media: amd: isp4: fix self-deadlock in isp4sd_pwron_and_init() error path media: amd: isp4: release partial allocations in isp4if_alloc_fw_gpumem() media: rcar-isp: Fix VSPX reference leaks media: rcar-isp: Release ISPCORE resources media: i2c: imx415: Release runtime PM reference on VBLANK error media: i2c: imx415: Return test pattern write errors media: renesas: vsp1: Declare index variables in for loop statement media: renesas: vsp1: Make reset control optional to support platforms without a reset line media: dt-bindings: media: renesas,vsp1: Document RZ/T2H and RZ/N2H SoCs media: dt-bindings: media: renesas,fcp: Document RZ/T2H and RZ/N2H SoCs media: nxp: imx8-isi: Add additional 32-bit RGB format support media: nxp: imx8-isi: Add 16-bit raw Bayer format support media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams media: nxp: imx8-isi: Use BIT_ULL() for 64-bit stream masks media: nxp: imx8-isi: Correct color map between V4L2 and ISI ... --- .../admin-guide/device-mapper/statistics.rst | 225 +++++++++++++++++++++ 1 file changed, 225 insertions(+) create mode 100644 Documentation/admin-guide/device-mapper/statistics.rst (limited to 'Documentation/admin-guide/device-mapper/statistics.rst') diff --git a/Documentation/admin-guide/device-mapper/statistics.rst b/Documentation/admin-guide/device-mapper/statistics.rst new file mode 100644 index 000000000..41ded0bc5 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/statistics.rst @@ -0,0 +1,225 @@ +============= +DM statistics +============= + +Device Mapper supports the collection of I/O statistics on user-defined +regions of a DM device. If no regions are defined no statistics are +collected so there isn't any performance impact. Only bio-based DM +devices are currently supported. + +Each user-defined region specifies a starting sector, length and step. +Individual statistics will be collected for each step-sized area within +the range specified. + +The I/O statistics counters for each step-sized area of a region are +in the same format as `/sys/block/*/stat` or `/proc/diskstats` (see: +Documentation/admin-guide/iostats.rst). But two extra counters (12 and 13) are +provided: total time spent reading and writing. When the histogram +argument is used, the 14th parameter is reported that represents the +histogram of latencies. All these counters may be accessed by sending +the @stats_print message to the appropriate DM device via dmsetup. + +The reported times are in milliseconds and the granularity depends on +the kernel ticks. When the option precise_timestamps is used, the +reported times are in nanoseconds. + +Each region has a corresponding unique identifier, which we call a +region_id, that is assigned when the region is created. The region_id +must be supplied when querying statistics about the region, deleting the +region, etc. Unique region_ids enable multiple userspace programs to +request and process statistics for the same DM device without stepping +on each other's data. + +The creation of DM statistics will allocate memory via kmalloc or +fallback to using vmalloc space. At most, 1/4 of the overall system +memory may be allocated by DM statistics. The admin can see how much +memory is used by reading: + + /sys/module/dm_mod/parameters/stats_current_allocated_bytes + +Messages +======== + + @stats_create [ ...] [ []] + Create a new region and return the region_id. + + + "-" + whole device + "+" + a range of 512-byte sectors + starting with . + + + "" + the range is subdivided into areas each containing + sectors. + "/" + the range is subdivided into the specified + number of areas. + + + The number of optional arguments + + + The following optional arguments are supported: + + precise_timestamps + use precise timer with nanosecond resolution + instead of the "jiffies" variable. When this argument is + used, the resulting times are in nanoseconds instead of + milliseconds. Precise timestamps are a little bit slower + to obtain than jiffies-based timestamps. + histogram:n1,n2,n3,n4,... + collect histogram of latencies. The + numbers n1, n2, etc are times that represent the boundaries + of the histogram. If precise_timestamps is not used, the + times are in milliseconds, otherwise they are in + nanoseconds. For each range, the kernel will report the + number of requests that completed within this range. For + example, if we use "histogram:10,20,30", the kernel will + report four numbers a:b:c:d. a is the number of requests + that took 0-10 ms to complete, b is the number of requests + that took 10-20 ms to complete, c is the number of requests + that took 20-30 ms to complete and d is the number of + requests that took more than 30 ms to complete. + + + An optional parameter. A name that uniquely identifies + the userspace owner of the range. This groups ranges together + so that userspace programs can identify the ranges they + created and ignore those created by others. + The kernel returns this string back in the output of + @stats_list message, but it doesn't use it for anything else. + If we omit the number of optional arguments, program id must not + be a number, otherwise it would be interpreted as the number of + optional arguments. + + + An optional parameter. A word that provides auxiliary data + that is useful to the client program that created the range. + The kernel returns this string back in the output of + @stats_list message, but it doesn't use this value for anything. + + @stats_delete + Delete the region with the specified id. + + + region_id returned from @stats_create + + @stats_clear + Clear all the counters except the in-flight i/o counters. + + + region_id returned from @stats_create + + @stats_list [] + List all regions registered with @stats_create. + + + An optional parameter. + If this parameter is specified, only matching regions + are returned. + If it is not specified, all regions are returned. + + Output format: + : + + precise_timestamps histogram:n1,n2,n3,... + + The strings "precise_timestamps" and "histogram" are printed only + if they were specified when creating the region. + + @stats_print [ ] + Print counters for each step-sized area of a region. + + + region_id returned from @stats_create + + + The index of the starting line in the output. + If omitted, all lines are returned. + + + The number of lines to include in the output. + If omitted, all lines are returned. + + Output format for each step-sized area of a region: + + + + counters + + The first 11 counters have the same meaning as + `/sys/block/*/stat or /proc/diskstats`. + + Please refer to Documentation/admin-guide/iostats.rst for details. + + 1. the number of reads completed + 2. the number of reads merged + 3. the number of sectors read + 4. the number of milliseconds spent reading + 5. the number of writes completed + 6. the number of writes merged + 7. the number of sectors written + 8. the number of milliseconds spent writing + 9. the number of I/Os currently in progress + 10. the number of milliseconds spent doing I/Os + 11. the weighted number of milliseconds spent doing I/Os + + Additional counters: + + 12. the total time spent reading in milliseconds + 13. the total time spent writing in milliseconds + + @stats_print_clear [ ] + Atomically print and then clear all the counters except the + in-flight i/o counters. Useful when the client consuming the + statistics does not want to lose any statistics (those updated + between printing and clearing). + + + region_id returned from @stats_create + + + The index of the starting line in the output. + If omitted, all lines are printed and then cleared. + + + The number of lines to process. + If omitted, all lines are printed and then cleared. + + @stats_set_aux + Store auxiliary data aux_data for the specified region. + + + region_id returned from @stats_create + + + The string that identifies data which is useful to the client + program that created the range. The kernel returns this + string back in the output of @stats_list message, but it + doesn't use this value for anything. + +Examples +======== + +Subdivide the DM device 'vol' into 100 pieces and start collecting +statistics on them:: + + dmsetup message vol 0 @stats_create - /100 + +Set the auxiliary data string to "foo bar baz" (the escape for each +space must also be escaped, otherwise the shell will consume them):: + + dmsetup message vol 0 @stats_set_aux 0 foo\\ bar\\ baz + +List the statistics:: + + dmsetup message vol 0 @stats_list + +Print the statistics:: + + dmsetup message vol 0 @stats_print 0 + +Delete the statistics:: + + dmsetup message vol 0 @stats_delete 0 -- cgit v1.3.1