1 /*
2  * Copyright (C) 2023 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <stdint.h>
20 #include <string>
21 
22 #include "utils/LruCache.h"
23 
24 // An interface to associate pid to a name. Implemented by looking up /proc/PID.
25 // To lower syscall impact, results are cached.
26 class ProcessNames {
27   public:
ProcessNames()28     ProcessNames() : cache(kMaxCacheEntries) {}
29 
30     ~ProcessNames() = default;
31 
32     // Returns the executable name or in the case of an app, the package name associated
33     // with a process pid.
34     std::string Get(uint64_t pid);
35 
36   private:
37     const std::string ReadCmdline(uint64_t pid);
38     const std::string ReadComm(uint64_t pid);
39     const std::string Resolve(uint64_t pid);
40 
41     // kMaxCacheEntries should be picked to keep the memory footprint low (1) and yield a
42     // high cache hit rate (2).
43     // 1. We cache executable name or package name, which account for roughly 20 characters
44     //    each. Using a 100 figure results in 2 KiB for cache storage.
45     // 2. Difficult to tune since it depends on how many process are alive and how much they
46     //    generate towards liblob. From manual testing, 100 entries resulted in 99% cache hit
47     //    with AOSP 34, right after boot, and one app active. We could monitor this value by
48     //    augmenting the protobuffer and have a cache hit boolean to generate a cache hit figure
49     //    on the workstation.
50     static const uint64_t kMaxCacheEntries = 100;
51     android::LruCache<uint64_t, std::string> cache;
52 };
53