In the pat_ref_elt struct, the pattern string is stored outside of the
node element, using a pointer to an strdup(). Not only this needlessly
wastes at least 16-24 bytes per entry (8 for the pointer, 8-16 for the
allocator), it also makes the tree descent less efficient since both
the node and the string have to be visited for each layer (hence at least
two cache lines). Let's use an ebmb storage and place the pattern right
at the end of the pat_ref_elt, making it a variable-sized element instead.
The set-map test below jumps from 173 to 182 kreq/s/core, and the memory
usage drops from 356 MB to 324 MB:
http-request set-map(/dev/null) %[rand(1000000)] 1
This is even more visible with large maps: after loading 16M IP addresses
into a map, the process uses this amount of memory:
- 3.15 GB with haproxy-2.8
- 4.21 GB with haproxy-2.9-dev11
- 3.68 GB with this patch
So that's a net saving of 32 bytes per entry here, which cuts in half the
extra cost of the tree, and loading a large map takes about 20% less time.
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