Documentation/kernel-hacking/false-sharing.rst

4 False Sharing
7 What is False Sharing
9 False sharing is related with cache mechanism of maintaining the data
44 reload the whole cache line over and over due to the 'sharing', even
48 false sharing.  One of these is a rw_semaphore 'mmap_lock' inside
52 There are two key factors for a harmful false sharing:
58 The sharing could be from totally unrelated kernel components, or
62 False Sharing Pitfalls
72 for false sharing:
85 False sharing could easily happen unless they are intentionally
87 critical workloads to detect false sharing affecting performance case
91 How to detect and analyze False Sharing
95 be further used to detect and pinpoint the possible false sharing
99 perf-c2c can capture the cache lines with most false sharing hits,
134 False sharing does not always need to be mitigated.  False sharing
140 False sharing hurting performance cases are seen more frequently with
154   sharing of other members.
156   - Commit 802f1d522d5f ("mm: page_counter: re-layout structure to reduce false sharing")
170 …ommit 7b1002f7cfe5 ("bcache: fixup bcache_dev_sectors_dirty_add() multithreaded CPU false sharing")
181 effects.  To avoid introducing false sharing when coding, it's better
190 and better add a comment stating the false sharing consideration.
192 One note is, sometimes even after a severe false sharing is detected
201 line sharing of data members.