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Although the code already uses lua_pcall() to call the Lua function lookup_policy(), it does not protect the code that sets the call frame of lookup_policy(). Therefore, if Lua runs out of memory (or any other error), the Lua state panics. Not only does this commit protect the code that sets the call frame of lookup_policy(), but it also runs Lua's garbage collector and retries lookup_policy() if the failure was due to a lack of memory.
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This commit closes #212
The TBL24 present in a FIB head takes 64MB. A Lua policy may have 4 FIBs: IPv4 source, IPv4 destination, IPv6 source, IPv6 destination. Therefore, an instance of a Lua policy may take more than 4 * 64MB = 256MB. A typical Grantor server has 2 instances of the GT Block. Therefore, The instances of a Lua policy may take more than 2 * 256MB = 512MB. During reloads or recreation of FIBs, the number of FIBs may double. Which requires more than 1GB of memory and reaches LuaJIT's limit of 1GB per process. This patch moves FIB heads to huge pages to avoid the problem decribed above. Moreover, having TBL24s in huge pages is also a performance improvement since it puts less load on the virtual memory subsystem and it is NUMA aware.
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This pull request has successfully reduced the memory pressure on Lua policies in production. |
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As Lua policies evolve, they may increase the memory pressure on Lua. This pull request releases some of this pressure.
The long-term solution is to upgrade to LuaJIT v2.1 and to enable GC64 once LuaJIT v2.1 is stable.