Android 这个关于 VSS/RSS/PSS/USS 的解释准确吗？
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Is this explanation about VSS/RSS/PSS/USS accurate?
提问by Victor S
I read an explanation about VSS/RSS/PSS/USS:
我读了一篇关于 VSS/RSS/PSS/USS 的解释：
The aim of this post is to provide information that will assist in interpreting memory reports from various tools so the true memory usage for Linux processes and the system can be determined.
这篇文章的目的是提供有助于解释来自各种工具的内存报告的信息，以便确定 Linux 进程和系统的真实内存使用情况。
Android has a tool called procrank (/system/xbin/procrank), which lists out the memory usage of Linux processes in order from highest to lowest usage. The sizes reported per process are VSS, RSS, PSS, and USS.
Android 有一个工具叫 procrank (/system/xbin/procrank)，它按使用率从高到低的顺序列出了 Linux 进程的内存使用情况。每个进程报告的大小是 VSS、RSS、PSS 和 USS。
For the sake of simplicity in this description, memory will be expressed in terms of pages, rather than bytes. Linux systems like ours manage memory in 4096 byte pages at the lowest level.
为了在本描述中简单起见，存储器将以页而不是字节来表示。像我们这样的 Linux 系统在最低级别以 4096 字节的页面管理内存。
VSS (reported as VSZ from ps) is the total accessible address space of a process. This size also includes memory that may not be resident in RAM like mallocs that have been allocated but not written to. VSS is of very little use for determing real memory usage of a process.
VSS（从 ps 报告为 VSZ）是进程的总可访问地址空间。此大小还包括可能不会驻留在 RAM 中的内存，如已分配但未写入的 malloc。VSS 很少用于确定进程的实际内存使用情况。
RSS is the total memory actually held in RAM for a process. RSS can be misleading, because it reports the total all of the shared libraries that the process uses, even though a shared library is only loaded into memory once regardless of how many processes use it. RSS is not an accurate representation of the memory usage for a single process.
RSS 是进程实际在 RAM 中保存的总内存。RSS 可能会产生误导，因为它报告了进程使用的所有共享库的总数，即使共享库只加载到内存中而不管有多少进程使用它。RSS 不能准确表示单个进程的内存使用情况。
PSS differs from RSS in that it reports the proportional size of its shared libraries, i.e. if three processes all use a shared library that has 30 pages, that library will only contribute 10 pages to the PSS that is reported for each of the three processes. PSS is a very useful number because when the PSS for all processes in the system are summed together, that is a good representation for the total memory usage in the system. When a process is killed, the shared libraries that contributed to its PSS will be proportionally distributed to the PSS totals for the remaining processes still using that library. In this way PSS can be slightly misleading, because when a process is killed, PSS does not accurately represent the memory returned to the overall system.
PSS 与 RSS 的不同之处在于它报告其共享库的比例大小，即如果三个进程都使用一个具有 30 页的共享库，则该库将只向 PSS 贡献 10 页，而这三个进程中的每一个都报告。PSS 是一个非常有用的数字，因为当系统中所有进程的 PSS 相加时，它可以很好地表示系统中的总内存使用量。当一个进程被终止时，为其 PSS 做出贡献的共享库将按比例分配到仍在使用该库的其余进程的 PSS 总数。这样 PSS 可能会有点误导，因为当一个进程被杀死时，PSS 并不能准确地表示返回给整个系统的内存。
USS is the total private memory for a process, i.e. that memory that is completely unique to that process. USS is an extremely useful number because it indicates the true incremental cost of running a particular process. When a process is killed, the USS is the total memory that is actually returned to the system. USS is the best number to watch when initially suspicious of memory leaks in a process.
USS 是进程的总私有内存，即该进程完全唯一的内存。USS 是一个非常有用的数字，因为它表示运行特定流程的真实增量成本。当一个进程被杀死时，USS 是实际返回给系统的总内存。当最初怀疑进程中的内存泄漏时，USS 是最好的观察数字。
For systems that have Python available, there is also a nice tool called smem that will report memory statistics including all of these categories.
对于具有可用 Python 的系统，还有一个名为 smem 的好工具，它将报告包括所有这些类别的内存统计信息。
# procrank
procrank
PID Vss Rss Pss Uss cmdline
481 31536K 30936K 14337K 9956K system_server
475 26128K 26128K 10046K 5992K zygote
526 25108K 25108K 9225K 5384K android.process.acore
523 22388K 22388K 7166K 3432K com.android.phone
574 21632K 21632K 6109K 2468K com.android.settings
521 20816K 20816K 6050K 2776K jp.co.omronsoft.openwnn
474 3304K 3304K 1097K 624K /system/bin/mediaserver
37 304K 304K 289K 288K /sbin/adbd
29 720K 720K 261K 212K /system/bin/rild
601 412K 412K 225K 216K procrank
1 204K 204K 185K 184K /init
35 388K 388K 182K 172K /system/bin/qemud
284 384K 384K 160K 148K top
27 376K 376K 148K 136K /system/bin/vold
261 332K 332K 123K 112K logcat
33 396K 396K 105K 80K /system/bin/keystore
32 316K 316K 100K 88K /system/bin/installd
269 328K 328K 95K 72K /system/bin/sh
26 280K 280K 93K 84K /system/bin/servicemanager
45 304K 304K 91K 80K /system/bin/qemu-props
34 324K 324K 91K 68K /system/bin/sh
260 324K 324K 91K 68K /system/bin/sh
600 324K 324K 91K 68K /system/bin/sh
25 308K 308K 88K 68K /system/bin/sh
28 232K 232K 67K 60K /system/bin/debuggerd
#
But I cannot find the original of this article, and I would like to know whether this explanation is accurate.
但是我找不到这篇文章的原文，我想知道这个解释是否准确。
采纳答案by Skeets
That sounds correct and also lines up with the description found here: http://elinux.org/Android_Memory_Usage
这听起来是正确的，并且与此处的描述一致：http: //elinux.org/Android_Memory_Usage
From the page...
从页面...
- Vss = virtual set size
- Rss = resident set size
- Pss = proportional set size
- Uss = unique set size
- Vss = 虚拟集大小
- Rss = 常驻集大小
- Pss = 比例集大小
- Uss = 独特的套装尺寸
