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Diffstat (limited to 'Documentation/bpf/map_hash.rst')
| -rw-r--r-- | Documentation/bpf/map_hash.rst | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/Documentation/bpf/map_hash.rst b/Documentation/bpf/map_hash.rst index d2343952f2cb..8606bf958a8c 100644 --- a/Documentation/bpf/map_hash.rst +++ b/Documentation/bpf/map_hash.rst @@ -233,10 +233,16 @@ attempts in order to enforce the LRU property which have increasing impacts on other CPUs involved in the following operation attempts: - Attempt to use CPU-local state to batch operations -- Attempt to fetch free nodes from global lists +- Attempt to fetch ``target_free`` free nodes from global lists - Attempt to pull any node from a global list and remove it from the hashmap - Attempt to pull any node from any CPU's list and remove it from the hashmap +The number of nodes to borrow from the global list in a batch, ``target_free``, +depends on the size of the map. Larger batch size reduces lock contention, but +may also exhaust the global structure. The value is computed at map init to +avoid exhaustion, by limiting aggregate reservation by all CPUs to half the map +size. With a minimum of a single element and maximum budget of 128 at a time. + This algorithm is described visually in the following diagram. See the description in commit 3a08c2fd7634 ("bpf: LRU List") for a full explanation of the corresponding operations: |