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| 1998 | There is no support for kqueue, as apparently it cannot be used to |
1998 | There is no support for kqueue, as apparently it cannot be used to |
| 1999 | implement this functionality, due to the requirement of having a file |
1999 | implement this functionality, due to the requirement of having a file |
| 2000 | descriptor open on the object at all times, and detecting renames, unlinks |
2000 | descriptor open on the object at all times, and detecting renames, unlinks |
| 2001 | etc. is difficult. |
2001 | etc. is difficult. |
| 2002 | |
2002 | |
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2003 | =head3 C<stat ()> is a synchronous operation |
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2004 | |
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2005 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
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2006 | the process. The exception are C<ev_stat> watchers - those call C<stat |
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2007 | ()>, which is a synchronous operation. |
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2008 | |
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2009 | For local paths, this usually doesn't matter: unless the system is very |
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2010 | busy or the intervals between stat's are large, a stat call will be fast, |
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2011 | as the path data is suually in memory already (except when starting the |
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2012 | watcher). |
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2013 | |
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2014 | For networked file systems, calling C<stat ()> can block an indefinite |
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2015 | time due to network issues, and even under good conditions, a stat call |
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2016 | often takes multiple milliseconds. |
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2017 | |
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2018 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
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2019 | paths, although this is fully supported by libev. |
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2020 | |
| 2003 | =head3 The special problem of stat time resolution |
2021 | =head3 The special problem of stat time resolution |
| 2004 | |
2022 | |
| 2005 | The C<stat ()> system call only supports full-second resolution portably, |
2023 | The C<stat ()> system call only supports full-second resolution portably, |
| 2006 | and even on systems where the resolution is higher, most file systems |
2024 | and even on systems where the resolution is higher, most file systems |
| 2007 | still only support whole seconds. |
2025 | still only support whole seconds. |
