{"id":1233,"date":"2022-06-20T22:37:39","date_gmt":"2022-06-20T14:37:39","guid":{"rendered":"https:\/\/summid.icu\/?p=1233"},"modified":"2022-07-19T21:34:53","modified_gmt":"2022-07-19T13:34:53","slug":"the-performance-characteristics-of-async-methods","status":"publish","type":"post","link":"https:\/\/summid.icu\/index.php\/2022\/06\/20\/the-performance-characteristics-of-async-methods\/","title":{"rendered":"\u63a2\u8ba8C#\u5f02\u6b65\u65b9\u6cd5\u4e4b\u6027\u80fd"},"content":{"rendered":"

\u672c\u6587\u624b\u52a8\u7ffb\u8bd1\u81ea\uff1aThe performance characteristics of async methods in C# – Developer Support (microsoft.com)<\/a><\/p>\n

\u5728\u524d\u4e24\u7bc7\u6587\u7ae0\u4e2d\uff0c\u6211\u4eec\u5b66\u4e60\u4e86<\/span>C#\u5f02\u6b65\u65b9\u6cd5\u7684\u539f\u7406<\/span><\/a><\/span>\uff0c\u8fd8\u4ecb\u7ecd\u4e86<\/span>C#\u7f16\u8bd1\u5668\u63d0\u4f9b\u4e86\u54ea\u4e9b\u5f02\u6b65\u65b9\u6cd5\u7684\u6269\u5c55\u9014\u5f84<\/span><\/a><\/span>\uff0c\u8ba9\u6211\u4eec\u80fd\u591f\u4fee\u6539\u5f02\u6b65\u65b9\u6cd5\u7684\u5de5\u4f5c\u6d41\u7a0b\u3002\u4eca\u5929\u6211\u4eec\u5c06\u63a2\u8ba8\u6709\u5173C#\u5f02\u6b65\u65b9\u6cd5\u7684\u6027\u80fd\u95ee\u9898\u3002<\/span><\/p>\n

\u901a\u8fc7<\/span>\u7b2c\u4e00\u7bc7\u6587\u7ae0<\/span><\/a><\/span>\uff0c\u4f60\u77e5\u9053\u4e86\u5728\u7f16\u8bd1\u5668\u5927\u8d39\u5468\u7ae0\u5730\u4f18\u5316\u540e\uff0c\u5f02\u6b65\u7f16\u7a0b\u4f53\u9a8c\u5df2\u7ecf\u975e\u5e38\u8fd1\u4f3c\u4e8e\u540c\u6b65\u7f16\u7a0b\u4e86\u3002\u4e3a\u4e86\u505a\u5230\u8fd9\u4e00\u70b9\uff0c\u7f16\u8bd1\u5668\u521b\u5efa\u4e86\u4e00\u4e2a\u72b6\u6001\u673a\uff0c\u5e76\u5c06\u5b83\u4f20\u7ed9\u5f02\u6b65\u65b9\u6cd5\u6784\u5efa\u5668\u201c <\/span>builder<\/code><\/span> \u201d\uff0c\u800c <\/span>builder<\/code><\/span> \u53c8\u4f1a\u8c03\u7528 <\/span>task awaiter<\/code><\/span> \uff0c\u7b49\u7b49\u3002\u663e\u7136\u8fd9\u4e9b\u64cd\u4f5c\u90fd\u4f1a\u4ea7\u751f\u6027\u80fd\u5f00\u9500\uff0c\u4f46\u6211\u4eec\u4e3a\u4e86\u5f97\u5230\u8fd9\u9879\u201c\u9ad8\u9636\u9b54\u6cd5\u201d\uff0c\u5177\u4f53\u4ed8\u51fa\u4e86\u591a\u5c11\u4ee3\u4ef7\uff1f<\/span><\/p>\n

\u5728 <\/span>Task<\/code><\/span> \u5e93\u8bde\u751f\u4e4b\u524d\uff0c\u5f02\u6b65\u64cd\u4f5c\u901a\u5e38\u662f\u975e\u5e38<\/span>\u7c97\u7c92\u5ea6<\/span><\/strong><\/span>\u7684\uff0c\u56e0\u6b64\u8fd9\u4e9b\u5f02\u6b65\u5bfc\u81f4\u7684\u6027\u80fd\u5f00\u9500\u51e0\u4e4e\u53ef\u4ee5\u88ab\u5ffd\u7565\u6389\u3002\u800c\u5230\u4e86\u4eca\u5929\uff0c\u751a\u81f3\u662f\u76f8\u5bf9\u7b80\u5355\u7684\u5e94\u7528\u7a0b\u5e8f\uff0c\u4e5f\u53ef\u80fd\u6bcf\u79d2\u6267\u884c\u7740\u6210\u767e\u4e0a\u5343\u6b21\u7684\u5f02\u6b65\u64cd\u4f5c\u3002<\/span>Task<\/code><\/span> \u5e93\u7684\u8bbe\u8ba1\u8003\u8651\u5230\u4e86\u5982\u6b64\u5e9e\u5927\u7684\u5de5\u4f5c\u8d1f\u8f7d\uff0c\u4f46\u5b83\u5176\u5b9e\u5e76\u4e0d\u662f\u9b54\u6cd5\uff0c\u5b83\u6709\u6027\u80fd\u4ee3\u4ef7\u3002\u901a\u5e38\u7528\u5f97\u5f88\u723d\u7684\u6280\u672f\uff0c\u4e00\u65e6\u6ee5\u7528\u8d77\u6765\u4e5f\u53ef\u80fd\u5bfc\u81f4\u5357\u8f95\u5317\u8f99\u7684\u540e\u679c\u3002<\/span><\/p>\n

\u4e3a\u4e86\u68c0\u6d4b\u5f02\u6b65\u65b9\u6cd5\u7684\u6027\u80fd\u5f00\u9500\uff0c\u6211\u4eec\u4f1a\u7528\u5230\u7b2c\u4e00\u7bc7\u6587\u7ae0\u4e2d\u7684\u7a0d\u4f5c\u4fee\u6539\u7684\u4f8b\u5b50\uff1a<\/span><\/p>\n\n\n

public class StockPrices\n{\n    private const int Count = 100;\n    private List<(string name, decimal price)> _stockPricesCache;\n \n    \/\/ Async version\n    public async Task<decimal> GetStockPriceForAsync(string companyId)\n    {\n        await InitializeMapIfNeededAsync();\n        return DoGetPriceFromCache(companyId);\n    }\n \n    \/\/ Sync version that calls async init\n    public decimal GetStockPriceFor(string companyId)\n    {\n        InitializeMapIfNeededAsync().GetAwaiter().GetResult();\n        return DoGetPriceFromCache(companyId);\n    }\n \n    \/\/ Purely sync version\n    public decimal GetPriceFromCacheFor(string companyId)\n    {\n        InitializeMapIfNeeded();\n        return DoGetPriceFromCache(companyId);\n    }\n \n    private decimal DoGetPriceFromCache(string name)\n    {\n        foreach (var kvp in _stockPricesCache)\n        {\n            if (kvp.name == name)\n            {\n                return kvp.price;\n            }\n        }\n \n        throw new InvalidOperationException($\"Can't find price for '{name}'.\");\n    }\n \n    [MethodImpl(MethodImplOptions.NoInlining)]\n    private void InitializeMapIfNeeded()\n    {\n        \/\/ Similar initialization logic.\n    }\n \n    private async Task InitializeMapIfNeededAsync()\n    {\n        if (_stockPricesCache != null)\n        {\n            return;\n        }\n \n        await Task.Delay(42);\n \n        \/\/ Getting the stock prices from the external source.\n        \/\/ Generate 1000 items to make cache hit somewhat expensive\n        _stockPricesCache = Enumerable.Range(1, Count)\n            .Select(n => (name: n.ToString(), price: (decimal)n))\n            .ToList();\n        _stockPricesCache.Add((name: \"MSFT\", price: 42));\n    }\n}<\/code><\/pre>\n\n\n
StockPrices<\/code><\/span> \u7c7b\u5bf9\u5916\u63d0\u4f9b\u67e5\u8be2\u80a1\u7968\u4ef7\u683c\u7684\u63a5\u53e3\uff0c\u5e76\u5728\u67e5\u8be2\u524d\u4f1a\u6839\u636e\u9700\u8981\u521d\u59cb\u5316\u7f13\u5b58\u3002\u8fd9\u4e2a\u4f8b\u5b50\u4e0e\u7b2c\u4e00\u7bc7\u6587\u7ae0\u7684\u533a\u522b\u662f\u5c06\u7f13\u5b58\u7684\u7ed3\u6784\u4ece\u5b57\u5178\u6362\u6210\u4e86\u6570\u7ec4\u3002\u4e3a\u4e86\u68c0\u6d4b\u5e76\u6bd4\u8f83\u5f02\u6b65\u65b9\u6cd5\u548c\u540c\u6b65\u65b9\u6cd5\u4e8c\u8005\u6027\u80fd\u5f00\u9500\u7684\u4f18\u52a3\uff0c\u8fd9\u4e9b\u201c\u65b9\u6cd5\u201d\u81f3\u5c11\u5f97\u505a\u4e00\u4e9b\uff08\u8017\u65f6\uff09\u5de5\u4f5c\uff0c\u6bd4\u5982\u5728\u80a1\u7968\u4ef7\u683c\u6a21\u578b\u4e2d\u8fdb\u884c\u7ebf\u6027\u641c\u7d22\u4e4b\u7c7b\u7684\u3002<\/span><\/p>\n
DoGetPriceFromCache<\/code><\/span> \u65b9\u6cd5\u662f\u6709\u610f\u4f7f\u7528\u666e\u901a\u5faa\u73af\u6784\u5efa\u7684\uff0c\u4ee5\u907f\u514d\u4efb\u4f55\u5185\u5b58\u5206\u914d\u3002<\/span><\/p>\n
\u9e7f\u6b7b\u8ab0\u624b\uff1f\uff01\u540c\u6b65\u65b9\u6cd5\u8207\u7570\u6b65\u65b9\u6cd5\u306e\u7d42\u6975\u5c0d\u6c7a\uff01<\/span><\/h2>\n
\u5728\u7b2c\u4e00\u4e2a <\/span>benchmark<\/code><\/span> \u4e2d\uff0c\u6211\u4eec\u4f1a\u6bd4\u8f83\u4e09\u4e2a\u5177\u4f53\u7684\u65b9\u6cd5\uff1a\u8c03\u7528\u4e86\u5f02\u6b65\u521d\u59cb\u5316\u65b9\u6cd5\u7684 <\/span>GetStockPriceForAsync<\/code><\/span> \uff1b\u540c\u6837\u8c03\u7528\u5f02\u6b65\u521d\u59cb\u5316\u65b9\u6cd5\uff0c\u4f46\u81ea\u8eab\u4e3a\u540c\u6b65\u65b9\u6cd5\u7684 <\/span>GetStockPriceFor<\/code><\/span> \uff1b\u4ee5\u53ca\u81ea\u8eab\u548c\u521d\u59cb\u5316\u65b9\u6cd5\u90fd\u4e3a\u540c\u6b65\u65b9\u6cd5\u7684 <\/span>GetPriceFromCacheFor<\/code><\/span> \u3002<\/span><\/p>\n\n\n
private readonly StockPrices _stockPrices = new StockPrices();\n \npublic SyncVsAsyncBenchmark()\n{\n    \/\/ Warming up the cache\n    _stockPrices.GetStockPriceForAsync(\"MSFT\").GetAwaiter().GetResult();\n}\n \n[Benchmark]\npublic decimal GetPricesDirectlyFromCache()\n{\n    return _stockPrices.GetPriceFromCacheFor(\"MSFT\");\n}\n \n[Benchmark(Baseline = true)]\npublic decimal GetStockPriceFor()\n{\n    return _stockPrices.GetStockPriceFor(\"MSFT\");\n}\n \n[Benchmark]\npublic decimal GetStockPriceForAsync()\n{\n    return _stockPrices.GetStockPriceForAsync(\"MSFT\").GetAwaiter().GetResult();\n}<\/code><\/pre>\n\n\n
\u7ed3\u679c\u5982\u4e0b\uff1a<\/p>\n\n\n
Method<\/th>Mean<\/th>Scaled<\/th>Gen0<\/th>Allocated<\/th><\/tr><\/thead>
GetPricesDirectlyFromCache<\/code><\/td>2.177us<\/td>0.96<\/td>–<\/td>0B<\/td><\/tr>
GetStockPriceFor<\/code><\/td>2.268us<\/td>1.00<\/td>–<\/td>0B<\/td><\/tr>
GetStockPriceForAsync<\/code><\/td>2.523us<\/td>1.11<\/td>0.0267<\/td>88B<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n
\u5f97\u51fa\u7684\u6570\u636e\u6709\u70b9\u610f\u601d\uff1a<\/span><\/p>\n