user/sven/linux.git/Documentation/block/queue-sysfs.txt, branch v4.14.136

block: remove the discard_zeroes_data flag

2017-04-08T17:25:38Z

Now that we use the proper REQ_OP_WRITE_ZEROES operation everywhere we can kill this hack. Signed-off-by: Christoph Hellwig Reviewed-by: Martin K. Petersen Reviewed-by: Hannes Reinecke Signed-off-by: Jens Axboe

blk-throttle: make throtl_slice tunable

2017-03-28T14:02:20Z

throtl_slice is important for blk-throttling. It's called slice internally but it really is a time window blk-throttling samples data. blk-throttling will make decision based on the samplings. An example is bandwidth measurement. A cgroup's bandwidth is measured in the time interval of throtl_slice. A small throtl_slice meanse cgroups have smoother throughput but burn more CPUs. It has 100ms default value, which is not appropriate for all disks. A fast SSD can dispatch a lot of IOs in 100ms. This patch makes it tunable. Since throtl_slice isn't a time slice, the sysfs name 'throttle_sample_time' reflects its character better. Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe

block: fix up io_poll documentation

2017-01-03T23:47:13Z

/sys/block//queue/io_poll is a boolean. Fix the docs. Signed-off-by: Jeff Moyer Signed-off-by: Jens Axboe

blk-wbt: allow reset of default latency through sysfs

2016-11-28T17:27:03Z

Allow a write of '-1' to reset the default latency target for a given device. This removes knowledge of the different default settings for rotational vs non-rotational from user space. Signed-off-by: Jens Axboe

block: document the 'io_poll_delay' queue sysfs file

2016-11-18T05:23:02Z

This was documented in the original commit, 64f1c21e86f7, but it never made it into the proper location for queue sysfs files. Signed-off-by: Jens Axboe

block: hook up writeback throttling

2016-11-10T20:53:40Z

Enable throttling of buffered writeback to make it a lot more smooth, and has way less impact on other system activity. Background writeback should be, by definition, background activity. The fact that we flush huge bundles of it at the time means that it potentially has heavy impacts on foreground workloads, which isn't ideal. We can't easily limit the sizes of writes that we do, since that would impact file system layout in the presence of delayed allocation. So just throttle back buffered writeback, unless someone is waiting for it. The algorithm for when to throttle takes its inspiration in the CoDel networking scheduling algorithm. Like CoDel, blk-wb monitors the minimum latencies of requests over a window of time. In that window of time, if the minimum latency of any request exceeds a given target, then a scale count is incremented and the queue depth is shrunk. The next monitoring window is shrunk accordingly. Unlike CoDel, if we hit a window that exhibits good behavior, then we simply increment the scale count and re-calculate the limits for that scale value. This prevents us from oscillating between a close-to-ideal value and max all the time, instead remaining in the windows where we get good behavior. Unlike CoDel, blk-wb allows the scale count to to negative. This happens if we primarily have writes going on. Unlike positive scale counts, this doesn't change the size of the monitoring window. When the heavy writers finish, blk-bw quickly snaps back to it's stable state of a zero scale count. The patch registers a sysfs entry, 'wb_lat_usec'. This sets the latency target to me met. It defaults to 2 msec for non-rotational storage, and 75 msec for rotational storage. Setting this value to '0' disables blk-wb. Generally, a user would not have to touch this setting. We don't enable WBT on devices that are managed with CFQ, and have a non-root block cgroup attached. If we have a proportional share setup on this particular disk, then the wbt throttling will interfere with that. We don't have a strong need for wbt for that case, since we will rely on CFQ doing that for us. Signed-off-by: Jens Axboe

doc: update block/queue-sysfs.txt entries

2016-08-11T15:37:23Z

Add descriptions for dax, io_poll, and write_same_max_bytes files. Signed-off-by: Joe Lawrence Signed-off-by: Jens Axboe

Doc: block: Fix a typo in queue-sysfs.txt

2016-06-28T20:14:16Z

This patch fix a spelling typo found in queue-sysfs.txt. Signed-off-by: Masanari Iida Signed-off-by: Jens Axboe

block: add ability to flag write back caching on a device

2016-04-12T21:46:27Z

Add an internal helper and flag for setting whether a queue has write back caching, or write through (or none). Add a sysfs file to show this as well, and make it changeable from user space. This will replace the (awkward) blk_queue_flush() interface that drivers currently use to inform the block layer of write cache state and capabilities. Signed-off-by: Jens Axboe Reviewed-by: Christoph Hellwig

block: make /sys/block//queue/discard_max_bytes writeable

2015-07-17T14:41:53Z

Lots of devices support huge discard sizes these days. Depending on how the device handles them internally, huge discards can introduce massive latencies (hundreds of msec) on the device side. We have a sysfs file, discard_max_bytes, that advertises the max hardware supported discard size. Make this writeable, and split the settings into a soft and hard limit. This can be set from 'discard_granularity' and up to the hardware limit. Add a new sysfs file, 'discard_max_hw_bytes', that shows the hw set limit. Reviewed-by: Jeff Moyer Signed-off-by: Jens Axboe