mirror of
https://github.com/torvalds/linux.git
synced 2024-12-27 05:11:48 +00:00
64 lines
2.3 KiB
Plaintext
64 lines
2.3 KiB
Plaintext
Queue sysfs files
|
|
=================
|
|
|
|
This text file will detail the queue files that are located in the sysfs tree
|
|
for each block device. Note that stacked devices typically do not export
|
|
any settings, since their queue merely functions are a remapping target.
|
|
These files are the ones found in the /sys/block/xxx/queue/ directory.
|
|
|
|
Files denoted with a RO postfix are readonly and the RW postfix means
|
|
read-write.
|
|
|
|
hw_sector_size (RO)
|
|
-------------------
|
|
This is the hardware sector size of the device, in bytes.
|
|
|
|
max_hw_sectors_kb (RO)
|
|
----------------------
|
|
This is the maximum number of kilobytes supported in a single data transfer.
|
|
|
|
max_sectors_kb (RW)
|
|
-------------------
|
|
This is the maximum number of kilobytes that the block layer will allow
|
|
for a filesystem request. Must be smaller than or equal to the maximum
|
|
size allowed by the hardware.
|
|
|
|
nomerges (RW)
|
|
-------------
|
|
This enables the user to disable the lookup logic involved with IO merging
|
|
requests in the block layer. Merging may still occur through a direct
|
|
1-hit cache, since that comes for (almost) free. The IO scheduler will not
|
|
waste cycles doing tree/hash lookups for merges if nomerges is 1. Defaults
|
|
to 0, enabling all merges.
|
|
|
|
nr_requests (RW)
|
|
----------------
|
|
This controls how many requests may be allocated in the block layer for
|
|
read or write requests. Note that the total allocated number may be twice
|
|
this amount, since it applies only to reads or writes (not the accumulated
|
|
sum).
|
|
|
|
read_ahead_kb (RW)
|
|
------------------
|
|
Maximum number of kilobytes to read-ahead for filesystems on this block
|
|
device.
|
|
|
|
rq_affinity (RW)
|
|
----------------
|
|
If this option is enabled, the block layer will migrate request completions
|
|
to the CPU that originally submitted the request. For some workloads
|
|
this provides a significant reduction in CPU cycles due to caching effects.
|
|
|
|
scheduler (RW)
|
|
--------------
|
|
When read, this file will display the current and available IO schedulers
|
|
for this block device. The currently active IO scheduler will be enclosed
|
|
in [] brackets. Writing an IO scheduler name to this file will switch
|
|
control of this block device to that new IO scheduler. Note that writing
|
|
an IO scheduler name to this file will attempt to load that IO scheduler
|
|
module, if it isn't already present in the system.
|
|
|
|
|
|
|
|
Jens Axboe <jens.axboe@oracle.com>, February 2009
|