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Diffstat (limited to 'NEWS')
| -rw-r--r-- | NEWS | 25 |
1 files changed, 25 insertions, 0 deletions
@@ -27,6 +27,31 @@ CHANGES WITH 240 in spe: non-transient services (i.e. those defined with unit files on disk) we will continue to default to Type=simple. + * The Linux kernel's current default RLIMIT_NOFILE resource limit for + userspace processes is set to 1024 (soft) and 4096 + (hard). Previously, systemd passed this on unmodified to all + processes it forked off. With this systemd release the hard limit + systemd passes on is increased to 256K, overriding the kernel's + defaults and substantially increasing the number of simultaneous file + descriptors unprivileged userspace processes can allocate. Note that + the soft limit remains at 1024 for compatibility reasons: the + traditional UNIX select() call cannot deal with file descriptors >= + 1024 and increasing the soft limit globally might thus result in + programs unexpectedly allocating a high file descriptor and thus + failing abnormally when attempting to use it with select() (of + course, programs shouldn't use select() anymore, and prefer + poll()/epoll, but the call unfortunately remains undeservedly popular + at this time). This change reflects the fact that file descriptor + handling in the Linux kernel has been optimized in more recent + kernels and allocating large numbers of them should be much cheaper + both in memory and in performance than it used to be. Programs that + want to take benefit of the increased limit have to "opt-in" into + high file descriptors explicitly by setting their soft limit to the + hard limit during initialization. Of course, when doing that they + must do this acknowledging the fact that they cannot use select() + anymore (and neither can any shared library they use — or any shared + library used by any shared library they use and so on). + CHANGES WITH 239: * NETWORK INTERFACE DEVICE NAMING CHANGES: systemd-udevd's "net_id" |