X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=man%2Fsystemd-readahead-replay.service.xml;h=67b41f5b26b5cff86ceb054d84cb6ae20a977c79;hp=3d7d9f542492564dd1185f64a5c014f4135c7b11;hb=05a2f6fefedd7254fd799502191d025d2908cf74;hpb=56ba3c78ae35065064c4289a0c8e22a81256af20 diff --git a/man/systemd-readahead-replay.service.xml b/man/systemd-readahead-replay.service.xml index 3d7d9f542..67b41f5b2 100644 --- a/man/systemd-readahead-replay.service.xml +++ b/man/systemd-readahead-replay.service.xml @@ -21,7 +21,8 @@ along with systemd; If not, see . --> - + systemd-readahead-replay.service @@ -56,7 +57,12 @@ systemd-readahead-collect.service systemd-readahead-done.service systemd-readahead-done.timer - /usr/lib/systemd/systemd-readahead + + /usr/lib/systemd/systemd-readahead/systemd-readahead + OPTIONS + COMMAND + DIRECTORY | FILE + @@ -67,7 +73,7 @@ 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 + 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. @@ -75,9 +81,9 @@ 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 + to end data collection. On this signal, this service will then sort the collected disk accesses and store - information about them disk in + information about them in /.readahead. Normally, both @@ -87,22 +93,106 @@ 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 + 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 + 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 + 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: + + + + + + Maximum number of + files to read ahead. Only valid + for thes collect + command. + + + + + + Maximum size of files + in bytes to read ahead. Only valid + for the collect + and replay + commands. + + + + + + Maximum time in microseconds + 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. For each file, the + output lists approximately how + much will be read ahead by + the replay + command. + + + + + + See Also