Android 最佳缓冲区大小
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Android Optimal Buffer Size
提问by L7ColWinters
In java there is an optimal buffer size of 32 Kb which is based solely on the cpu architecture being used. On Android phones does the Dalvik VM dynamically know the proper cache of the cpu to get the largest buffer size independent of the many different phones out there? If so how would I figure that out at runtime?
在 java 中有一个 32 Kb 的最佳缓冲区大小，它完全基于所使用的 CPU 架构。在 Android 手机上，Dalvik VM 是否动态地知道 CPU 的正确缓存，以获得独立于许多不同手机的最大缓冲区大小？如果是这样，我将如何在运行时弄清楚？
Say I want to optimize a audio recording activity by making the buffer the largest it can be and also the fastest. I know you can get the minimal size for it but what about the optimal size?
假设我想通过使缓冲区最大和最快来优化录音活动。我知道你可以获得最小的尺寸，但最佳尺寸呢？
回答by Joon Hong
Maybe it depends on what device you have or mind.
也许这取决于您拥有或介意的设备。
However, experimentally, 8K < buffer size < 32Kdoes work well and there are significant performance improvements under 8K. Somewhat interesting is that some data with buffer > 64K showed poorer performance than data with under 64K buffer
但是，在实验上，8K < 缓冲区大小 < 32K效果很好，并且在 8K 下有显着的性能改进。有趣的是，一些缓冲区大于 64K 的数据表现出比缓冲区低于 64K 的数据更差的性能
(I've tested on several android devices and tried to read 20MB binary file with various buffer size.)
（我已经在多个 android 设备上进行了测试，并尝试读取具有各种缓冲区大小的 20MB 二进制文件。）
Here's exp result and you'd better to paste them to spreadsheet if you wanna convert data in pretty form. header means buffer sizeand units are millisecond
这是 exp 结果，如果您想以漂亮的形式转换数据，最好将它们粘贴到电子表格中。标头表示缓冲区大小，单位为毫秒
graph: http://fb.com/photo.php?fbid=468345876512381
图：http: //fb.com/photo.php?fbid=468345876512381
128 256 512 1K 2K 4K 8K 16K 32K 64K 128K 256K 512K 1M 2M 4M 8M 16M
Galaxy S 4047 3060 269 155 100 65 64 52 51 45 47 50 49 43 44 46 45 58
Optimus LTE 1178 617 322 172 101 65 47 42 41 35 36 39 44 61 56 51 72 60
HTC EVO 3971 1884 941 480 251 141 95 69 56 50 48 55 50 49 48 48 48 47
Galaxy S2 750 383 210 123 74 50 41 37 35 34 34 37 39 44 46 44 45 44
Galaxy Nexus 2272 1216 659 341 187 108 70 52 41 38 38 45 44 54 56 66 68 58
Galaxy Note 1549 799 404 220 127 75 58 54 52 56 52 45 44 62 43 39 44 46
InputStream in = openFileInput(FILE_NAME);
startTime = System.currentTimeMillis();
while (in.read(buffer) > 0) {
readCount++;
}
elapsedTime = System.currentTimeMillis() - startTime;
