Domenico Cerasuolo d5dca19776 sched/psi: Allow unprivileged polling of N*2s period ... [ Upstream commit d82caa2735 ] PSI offers 2 mechanisms to get information about a specific resource pressure. One is reading from /proc/pressure/<resource>, which gives average pressures aggregated every 2s. The other is creating a pollable fd for a specific resource and cgroup. The trigger creation requires CAP_SYS_RESOURCE, and gives the possibility to pick specific time window and threshold, spawing an RT thread to aggregate the data. Systemd would like to provide containers the option to monitor pressure on their own cgroup and sub-cgroups. For example, if systemd launches a container that itself then launches services, the container should have the ability to poll() for pressure in individual services. But neither the container nor the services are privileged. This patch implements a mechanism to allow unprivileged users to create pressure triggers. The difference with privileged triggers creation is that unprivileged ones must have a time window that's a multiple of 2s. This is so that we can avoid unrestricted spawning of rt threads, and use instead the same aggregation mechanism done for the averages, which runs independently of any triggers. Suggested-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Link: https://lore.kernel.org/r/20230330105418.77061-5-cerasuolodomenico@gmail.com Stable-dep-of: aff037078e ("sched/psi: use kernfs polling functions for PSI trigger polling") Signed-off-by: Sasha Levin <sashal@kernel.org>		2023-07-27 08:50:38 +02:00
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cgroupstats.rst	Documentation: Replace lkml.org links with lore	2021-01-11 12:47:38 -07:00
delay-accounting.rst	filemap: make the accounting of thrashing more consistent	2022-09-26 19:46:06 -07:00
index.rst	docs: add some documentation dirs to the driver-api book	2019-07-15 11:03:02 -03:00
psi.rst	sched/psi: Allow unprivileged polling of N*2s period	2023-07-27 08:50:38 +02:00
taskstats-struct.rst	docs: accounting: convert to ReST	2019-07-15 09:20:25 -03:00
taskstats.rst	docs: accounting: convert to ReST	2019-07-15 09:20:25 -03:00