allow IOBuf::append_user_data specifying any valid address in registered rdma memory region #1999
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… rdma memory region
Tuvie
changed the title
wwbmmm
reviewed
Nov 17, 2022
| @@ -99,37 +99,41 @@ static ibv_device** g_devices = NULL; | |||
| static ibv_context* g_context = NULL; | |||
| static SocketId g_async_socket; | |||
| static ibv_pd* g_pd = NULL; | |||
| static std::vector<ibv_mr*>* g_mrs = NULL; | |||
| static std::vector<ibv_mr*>* g_mrs = NULL; // mr registered by brpc | |||
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可以按照地址排列成有序集合，用二分法查找更快
这么用是为了避免在后续GetLkey的时候上锁，数组虽然效率不好但是线程间竞争影响可忽略。高级一点的数据结构无锁化高效实现没想好怎么做。或者就是把线程竞争的处理留给上层的应用去考虑。有什么建议么？
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其实针对这个问题，我有点想把IOBuf的结构改改。每一段user_data可能对应不同的lkey。如果这个lkey能存放在IOBuf的元数据里面，就不需要这个lookup了。你觉得如何？
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append_user_data加个lkey的参数么？我觉得ok，可以问问那个用户
| @@ -1061,7 +1068,10 @@ TEST_F(RdmaTest, server_miss_after_ack) { | |||
| usleep(100000); | |||
| ASSERT_EQ(rdma::RdmaEndpoint::ESTABLISHED, s->_rdma_ep->_state); | |||
| ASSERT_EQ(4, read(acc_fd, data, 4)); | |||
| #pragma GCC diagnostic push | |||
| #pragma GCC diagnostic ignored "-Wstrict-aliasing" | |||
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(uint32_t*)data改成(uint32_t*)(void*)data应该就不会报错了
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What problem does this PR solve?
Issue Number: 1995
Problem Summary: When using IOBuf::append_user_data, if the application specify a buffer with an offset over the base address registered with rdma::RegisterMemoryForRdma, brpc reports a failure for invalid memory region.
What is changed and the side effects?
Changed: Use a fixed-length array to manage the user-defined memory regions. To lookup the lkey for a buffer specified in append_user_data, brpc scans the array to find the correct region. To guarantee the performance of lkey lookup, we avoid using mutex for the lookup in this array.
Side effects:
Performance effects(性能影响):
Breaking backward compatibility(向后兼容性): To guarantee the performance of lkey (linear) lookup, brpc only support at most 16 user-defined memory regions. The application should maintain the user-defined buffer with a memory pool and register the pool one time. And since the lookup is not guarded with a mutex, the application should try not to register or deregister memory during rpc processing.
Check List: