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9023691d75
We are starting to deploy mmap_lock tracepoint monitoring across our fleet and the early results showed that these tracepoints are consuming significant amount of CPUs in kernfs_path_from_node when enabled. It seems like the kernel is trying to resolve the cgroup path in the fast path of the locking code path when the tracepoints are enabled. In addition for some application their metrics are regressing when monitoring is enabled. The cgroup path resolution can be slow and should not be done in the fast path. Most userspace tools, like bpftrace, provides functionality to get the cgroup path from cgroup id, so let's just trace the cgroup id and the users can use better tools to get the path in the slow path. Link: https://lkml.kernel.org/r/20241125171617.113892-1-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> Reviewed-by: Yosry Ahmed <yosryahmed@google.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Reviewed-by: Axel Rasmussen <axelrasmussen@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.