diff options
Diffstat (limited to 'man')
| -rw-r--r-- | man/sd_journal_get_fd.xml | 24 |
1 files changed, 12 insertions, 12 deletions
diff --git a/man/sd_journal_get_fd.xml b/man/sd_journal_get_fd.xml index 52360c76c3..6ca45c4e8e 100644 --- a/man/sd_journal_get_fd.xml +++ b/man/sd_journal_get_fd.xml @@ -151,18 +151,18 @@ else { <function>poll()</function> and <function>sd_journal_process()</function> into one.</para> - <para><function>sd_journal_reliable_fd()</function> may be used to - check whether the wakeup events from the file descriptor returned - by <function>sd_journal_get_fd()</function> are known to be - immediately triggered. On certain file systems where file change - events from the OS are not available (such as NFS) changes need to - be polled for repeatedly, and hence are detected only with a - certain latency. This call will return a positive value if the - journal changes are detected immediately and zero when they need - to be polled for and hence might be noticed only with a certain - latency. Note that there is usually no need to invoke this function - directly as <function>sd_journal_get_timeout()</function> on these - file systems will ask for timeouts explicitly anyway.</para> + <para><function>sd_journal_reliable_fd()</function> may be used to check whether the wake-up events from + the file descriptor returned by <function>sd_journal_get_fd()</function> are known to be quickly + triggered. On certain file systems where file change events from the OS are not available (such as NFS) + changes need to be polled for repeatedly, and hence are detected only with a considerable latency. This + call will return a positive value if the journal changes are detected quickly and zero when they need to + be polled for. Note that there is usually no need to invoke this function directly as + <function>sd_journal_get_timeout()</function> will request appropriate timeouts anyway.</para> + + <para>Note that all of the above change notification interfaces do not report changes + instantly. Latencies are introduced for multiple reasons: as mentioned certain storage backends require + time-based polling, in other cases wake-ups are optimized by coalescing events, and the OS introduces + additional IO/CPU scheduling latencies.</para> </refsect1> <refsect1> |