0f0869bca3
Without this patch, mountd would delete/load all exports from the exports file(s) when it receives a SIGHUP. This works fine for small exports file(s), but can take several seconds to do when there are large numbers (10000+) of exported file systems. Most of this time is spent doing the system calls that delete/export each of these file systems. When the "-S" option has been specified (the default these days), the nfsd threads are suspended for several seconds while the reload is done. This patch changes mountd so that it only does system calls for file systems where the exports have been changed/added/deleted as compared to the exports done for the previous load/reload of the exports file(s). Basically, when SIGHUP is posted to mountd, it saves the exportlist structures from the previous load and creates a new set of structures from the current exports file(s). Then it compares the current with the previous and only does system calls for cases that have been changed/added/deleted. The nfsd threads do not need to be suspended until the comparison step is being done. This results in a suspension period of milliseconds for a server with 10000+ exported file systems. There is some code using a LOGDEBUG() macro that allow runtime debugging output via syslog(LOG_DEBUG,...) that can be enabled by creating a file called /var/log/mountd.debug. This code is expected to be replaced with code that uses dtrace by cy@ in the near future, once issues w.r.t. dtrace in stable/12 have been resolved. The patch should not change the usage of the exports file(s), but improves the performance of reloading large exports file(s) where there are only a small number of changes done to the file(s). Tested by: pen@lysator.liu.se PR: 237860 Reviewed by: kib MFC after: 1 month Relnotes: yes Differential Revision: https://reviews.freebsd.org/D20487 |
||
|---|---|---|
| .. | ||
| exports.5 | ||
| Makefile | ||
| Makefile.depend | ||
| mountd.8 | ||
| mountd.c | ||
| netgroup.5 | ||
| pathnames.h | ||