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Interlink: optimize rebalance #62

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Interlink: optimize rebalance #62

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8f5569b
struct freelist: change nfree/max to 32-bit uint (from 64-bit)
eugeneia Nov 8, 2018
a62efa7
core.packet: use ffi.copy to rebalance freelists
eugeneia Nov 8, 2018
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45 changes: 35 additions & 10 deletions src/core/packet.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -52,8 +52,7 @@ local max_packets = 1e6
ffi.cdef([[
struct freelist {
int32_t lock[1];
uint64_t nfree;
uint64_t max;
uint32_t nfree, max;
struct packet *list[]]..max_packets..[[];
};
]])
Expand Down Expand Up @@ -84,6 +83,22 @@ local function freelist_nfree(freelist)
return freelist.nfree
end

local function freelist_room(freelist)
return freelist.max - freelist.nfree
end

local function freelist_move (dst, src, n)
-- Safety check
if _G.developer_debug then
assert(dst.nfree + n <= dst.max, "freelist overflow")
assert(n <= src.nfree, "freelist underflow")
end
ffi.copy(dst.list + dst.nfree, src.list + (src.nfree-n),
n * ffi.sizeof("struct packet *"))
dst.nfree = dst.nfree + n
src.nfree = src.nfree - n
end

local function freelist_lock(freelist)
sync.lock(freelist.lock)
end
Expand All @@ -109,10 +124,9 @@ end
function rebalance_freelists ()
if group_fl and freelist_nfree(packets_fl) > packets_allocated then
freelist_lock(group_fl)
while freelist_nfree(packets_fl) > packets_allocated
and not freelist_full(group_fl) do
freelist_add(group_fl, freelist_remove(packets_fl))
end
local surplus = math.min(freelist_nfree(packets_fl) - packets_allocated,
freelist_room(group_fl))
freelist_move(group_fl, packets_fl, surplus)
freelist_unlock(group_fl)
end
end
Expand All @@ -122,10 +136,8 @@ function allocate ()
if freelist_nfree(packets_fl) == 0 then
if group_fl then
freelist_lock(group_fl)
while freelist_nfree(group_fl) > 0
and freelist_nfree(packets_fl) < packets_allocated do
freelist_add(packets_fl, freelist_remove(group_fl))
end
local deficit = math.min(packets_allocated, freelist_nfree(group_fl))
freelist_move(packets_fl, group_fl, deficit)
freelist_unlock(group_fl)
end
if freelist_nfree(packets_fl) == 0 then
Expand Down Expand Up @@ -320,4 +332,17 @@ function selftest ()
default_headroom + 2, packet_alignment - 2)
check_slow_shift(packet_alignment, shiftleft,
packet_alignment - default_headroom, default_headroom)

local fl1 = freelist_create("test.freelist")
local fl2 = freelist_create("test2.freelist")
freelist_add(fl1, ffi.cast("struct packet *", 42))
freelist_add(fl1, ffi.cast("struct packet *", 43))
freelist_add(fl2, ffi.cast("struct packet *", 44))
freelist_move(fl2, fl1, 2)
assert(freelist_nfree(fl1) == 0)
assert(freelist_nfree(fl2) == 3)
assert(freelist_remove(fl2) == ffi.cast("struct packet *", 43))
assert(freelist_remove(fl2) == ffi.cast("struct packet *", 42))
assert(freelist_remove(fl2) == ffi.cast("struct packet *", 44))
assert(freelist_nfree(fl2) == 0)
end