other versions
- wheezy-backports 204-14~bpo70+1
- jessie 215-17+deb8u7
SYSTEMD-READAHEAD-REPLAY.SERVICE(8) | systemd-readahead-replay.service | SYSTEMD-READAHEAD-REPLAY.SERVICE(8) |
NAME¶
systemd-readahead-replay.service, systemd-readahead-collect.service, systemd-readahead-done.service, systemd-readahead-done.timer, systemd-readahead - Disk read ahead logicSYNOPSIS¶
systemd-readahead-replay.service systemd-readahead-collect.service systemd-readahead-done.service systemd-readahead-done.timer/usr/lib/systemd/systemd-readahead/systemd-readahead
[OPTIONS...] COMMAND [DIRECTORY | FILE]
DESCRIPTION¶
systemd-readahead-collect.service is a service that collects disk usage patterns at boot time. systemd-readahead-replay.service is a service that replays this access data collected at the subsequent boot. Since disks tend to be magnitudes slower than RAM this is intended to improve boot speeds by pre-loading early at boot all data on disk that is known to be read for the complete boot process. systemd-readahead-done.service is executed a short while after boot completed and signals systemd-readahead-collect.service to end data collection. On this signal this service will then sort the collected disk accesses and store information about them disk in /.readahead. Normally, both systemd-readahead-collect.service and systemd-readahead-replay.service are activated at boot so that access patterns from the preceding boot are replayed and new data collected for the subsequent boot. However, on read-only media where the collected data cannot be stored it might be a good idea to disable systemd-readahead-collect.service. On rotating media, when replaying disk accesses at early boot systemd-readahead-replay.service will order read requests by their location on disk. On non-rotating media, they will be ordered by their original access timestamp. If the file system supports it systemd-readahead-collect.service will also defragment and rearrange files on disk to optimize subsequent boot times.OPTIONS¶
systemd-readahead understands the following options: -h, --helpPrints a short help text and exits.
--max-files=
Maximum number of files to read ahead. Only
valid for thes collect command.
--file-size-max=
Maximum size of files (in bytes) to read
ahead. Only valid for the collect and replay commands.
--timeout=
Maximum time (in usec) to to spend collecting
data. Only valid for the collect command.
COMMANDS¶
The following commands are understood by systemd-readahead: collect [DIRECTORY]Collect read-ahead data on early boot. When
terminating it will write out a pack file to the indicated directory
containing the read-ahead data.
replay [DIRECTORY]
Perform read-ahead on the specified directory
tree.
analyze [FILE]
Dumps the content of the read-ahead pack file
to the terminal. The output lists approximately for each file how much will be
read-ahead by the replay command.
SEE ALSO¶
systemd 204 |