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Diffstat (limited to 'Documentation/block/queue-sysfs.txt')
| -rw-r--r-- | Documentation/block/queue-sysfs.txt | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt index 2a3904030dea..51642159aedb 100644 --- a/Documentation/block/queue-sysfs.txt +++ b/Documentation/block/queue-sysfs.txt @@ -58,6 +58,20 @@ When read, this file shows the total number of block IO polls and how many returned success. Writing '0' to this file will disable polling for this device. Writing any non-zero value will enable this feature. +io_poll_delay (RW) +------------------ +If polling is enabled, this controls what kind of polling will be +performed. It defaults to -1, which is classic polling. In this mode, +the CPU will repeatedly ask for completions without giving up any time. +If set to 0, a hybrid polling mode is used, where the kernel will attempt +to make an educated guess at when the IO will complete. Based on this +guess, the kernel will put the process issuing IO to sleep for an amount +of time, before entering a classic poll loop. This mode might be a +little slower than pure classic polling, but it will be more efficient. +If set to a value larger than 0, the kernel will put the process issuing +IO to sleep for this amont of microseconds before entering classic +polling. + iostats (RW) ------------- This file is used to control (on/off) the iostats accounting of the @@ -169,5 +183,14 @@ This is the number of bytes the device can write in a single write-same command. A value of '0' means write-same is not supported by this device. +wb_lat_usec (RW) +---------------- +If the device is registered for writeback throttling, then this file shows +the target minimum read latency. If this latency is exceeded in a given +window of time (see wb_window_usec), then the writeback throttling will start +scaling back writes. Writing a value of '0' to this file disables the +feature. Writing a value of '-1' to this file resets the value to the +default setting. + Jens Axboe <jens.axboe@oracle.com>, February 2009 |