core.packet: configurable freelist size

src/core/packet.lua

@@ -52,24 +52,28 @@ end
 
 -- Freelist containing empty packets ready for use.
 
-local max_packets = 1e6
+local default_max_packets = 1e6
 
 ffi.cdef([[
 struct freelist {
  int nfree;
  int max;
- struct packet *list[]]..max_packets..[[];
+ struct packet *list[?];
 };
 ]])
 
-local function freelist_create(name)
- local fl = shm.create(name, "struct freelist")
+local function freelist_create(name, max_packets)
+ max_packets = max_packets or default_max_packets
+ local fl = shm.create(name, "struct freelist", max_packets)
  fl.max = max_packets
  return fl
 end
 
 local function freelist_open(name, readonly)
- return shm.open(name, "struct freelist", readonly)
+ local fl = shm.open(name, "struct freelist", 'read-only', 1)
+ local max = fl.max
+ shm.unmap(fl)
+ return shm.open(name, "struct freelist", readonly, max)
 end
 
 local function freelist_full(freelist)
@@ -104,8 +108,13 @@ local packets_allocated = 0
 local packets_fl, group_fl
 
 -- Call to ensure packet freelist is enabled.
-function initialize ()
- packets_fl = freelist_create("engine/packets.freelist")
+function initialize (max_packets)
+ if packets_fl then
+ assert(packets_fl.nfree == 0, "freelist is already in use")
+ shm.unmap(packets_fl)
+ shm.unlink("engine/packets.freelist")
+ end
+ packets_fl = freelist_create("engine/packets.freelist", max_packets)
 end
 
 -- Call to ensure group freelist is enabled.
@@ -310,7 +319,7 @@ end
 
 function preallocate_step()
  assert(packets_allocated + packet_allocation_step
- <= max_packets - group_fl_chunksize,
+ <= packets_fl.max - group_fl_chunksize,
  "packet allocation overflow")
 
  for i=1, packet_allocation_step do
@@ -321,6 +330,12 @@ function preallocate_step()
 end
 
 function selftest ()
+ initialize(10000)
+ assert(packets_fl.max == 10000)
+ allocate()
+ local ok, err = pcall(initialize)
+ assert(not ok and err:match("freelist is already in use"))
+
  assert(is_aligned(0, 1))
  assert(is_aligned(1, 1))
  assert(is_aligned(2, 1))