| page.title=Data Usage Tags Explained |
| @jd:body |
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| <p>Tags represent one of the metrics the data usage counters will be |
| tracked against. By default, and implicitly, a tag is just based on |
| the UID. The UID is used as the base for policing, and cannot be |
| ignored. So a tag will always at least represent a UID (uid_tag). A |
| tag can be explicitly augmented with an "accounting tag" which is |
| associated with a UID. User space can use |
| <code>TrafficStats.setThreadStatsTag()</code> to set the acct_tag portion of the |
| tag which is then used with sockets: all data belonging to that |
| socket will be counted against the tag. The policing is then based on |
| the tag's uid_tag portion, and stats are collected for the acct_tag |
| portion separately.</p> |
| <p>Without explicit tagging, the qtaguid module will assume the |
| <code>default_tag: {acct_tag=0, uid_tag=10003}</code></p> |
| <pre><code> a: {acct_tag=1, uid_tag=10003} |
| b: {acct_tag=2, uid_tag=10003} |
| c: {acct_tag=3, uid_tag=10003} |
| </code></pre> |
| <p><code>a, b, c…</code> represent explicit tags associated with specific sockets.</p> |
| <p><code>default_tag (acct_tag=0)</code> is the default accounting tag that contains |
| the total traffic for that uid, including all untagged |
| traffic, and is typically used to enforce policing/quota rules.</p> |
| <p>These tags can be used to profile the network traffic of an |
| application into separate logical categories (at a network socket |
| level). Such tags can be removed, reapplied, or modified during |
| runtime.</p> |
| <p>The qtaguid module has been implemented on <a href="https://android-review.googlesource.com/#/q/project:kernel/common+branch:android-3.0,n,z">kernel/common branch of |
| android-3.0</a></p> |
