1371205 - Add telemetry about MediaCacheStream initial notified lengths (from HTTP header)

Status: RESOLVED FIXED

(Core :: Audio/Video: Playback, enhancement)

Description

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

An upcoming bug will aim to keep small-enough media resources completely in memory, bypassing the shared MediaCache. We will need to decide on a default "small-enough" threshold.

We already know from MEDIACACHESTREAM_LENGTH_KB (bug 1369538) that 94% of all MediaCacheStreams only use 16MB or less, but the probe is not very precise and we only have two buckets covering 16MB.

The new probe will capture the initial length notification only (from the HTTP header), as that is what we will use in the upcoming feature, up to 16MB.
This should give us a good spread of numbers (64 buckets of 256KB), to select the best default. -- Caching more in memory would probably be too greedy for now!

Comment 1

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Attachment: Bug 1371205 - MEDIACACHESTREAM_NOTIFIED_LENGTH captures the HTTP header length given to MediaCacheStream -

Review commit: https://reviewboard.mozilla.org/r/147064/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/147064/

Comment 2

[JW Wang [:jwwang] [:jw_wang]]

Comment on attachment 8875639 [details]
Bug 1371205 - MEDIACACHESTREAM_NOTIFIED_LENGTH captures the HTTP header length given to MediaCacheStream -

https://reviewboard.mozilla.org/r/147064/#review151200

::: dom/media/MediaCache.cpp:1766
(Diff revision 1)
>  void
>  MediaCacheStream::NotifyDataLength(int64_t aLength)
>  {
>    NS_ASSERTION(NS_IsMainThread(), "Only call on main thread");
>  
> +  if (mStreamLength < 0 && aLength >= 0) {

Why checking |mStreamLength < 0|?

Comment 3

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Comment on attachment 8875639 [details]
Bug 1371205 - MEDIACACHESTREAM_NOTIFIED_LENGTH captures the HTTP header length given to MediaCacheStream -

https://reviewboard.mozilla.org/r/147064/#review151200

> Why checking |mStreamLength < 0|?

I want to capture the very first notification, before mStreamLength could have been set by another notification, or by actual data arriving.

Comment 4

[François Marier [:francois]]

Comment on attachment 8875639 [details]
Bug 1371205 - MEDIACACHESTREAM_NOTIFIED_LENGTH captures the HTTP header length given to MediaCacheStream -

https://reviewboard.mozilla.org/r/147064/#review151402

datareview+

Comment 5

[Chris Pearce [:cpearce (Not reading bugmail)]]

Comment on attachment 8875639 [details]
Bug 1371205 - MEDIACACHESTREAM_NOTIFIED_LENGTH captures the HTTP header length given to MediaCacheStream -

https://reviewboard.mozilla.org/r/147064/#review152180

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/acacb9c914f1
MEDIACACHESTREAM_NOTIFIED_LENGTH captures the HTTP header length given to MediaCacheStream - r=cpearce,francois

Comment 7

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/acacb9c914f1