982968 - [buri] run gralloc framebuffer thread at RT priority to minimize fb_lockBuffer()

Status: RESOLVED INCOMPLETE

(Firefox OS Graveyard :: GonkIntegration, defect, P3)

Description

[Ben Kelly [:bkelly, not reviewing]]

Attachment: fb_rt_priority.patch

As discussed in bug 980027 we would like the ability to possibly run the gecko compositor thread at RT priority.  Currently, however, the buri gonk firmware interacts poorly with this schedule policy.

In particular it forces us into a state where we hit the fb_lockBuffer() issue described in bug 980171.  For example, see this profile:

  http://people.mozilla.org/~bgirard/cleopatra/#report=3948400a8133b559f3850e164f7e28b27c57d9ff

This is quite bad with composites consistently taking 30ms.

If we update the disp_loop() thread priority in the gralloc framebuffer to the same RT priority, however, things get dramatically better.  Not only do we avoid the 30ms composites, but we see a reduction of the delays currently experienced in bug 980171.

  http://people.mozilla.org/~bgirard/cleopatra/#report=af28b72e2a28a81637691799f5d7b0149367a369

Whats more, it appears that the framebuffer thread at RT1 and the compositor thread without RT priority also works very well:

  http://people.mozilla.org/~bgirard/cleopatra/#report=1dbfd12c36c0b7d6a6223a8b24d4dff8965ef13a

Therefore I think we should investigate ways to change the gralloc framebuffer's disp_loop() thread to RT priority 1.

The attached patch shows the change I made to the gralloc library.

Comment 1

[Ben Kelly [:bkelly, not reviewing]]

Comment on attachment 8390193 [details] [diff] [review]
fb_rt_priority.patch

Sushil, I know buri is not a priority at the moment, but what is the possibility of getting a patch like this upstreamed?  Or is there another way for us to get its thread ID and manually adjust its priority from gecko?

Thanks!

Comment 2

[Sushil]

Ben,

If you are not seeing any issues in any other IOCTL by bumping up the priority, it should be OK to have this. Regarding patch up-streaming, Diego should comment on this because I do not know if we officially support ICS HAL based devices currently.

Comment 3

[Diego Wilson [:diego]]

Are you planning on doing this in v1.3 or v1.4? Maybe mvines can comment on the state of CAF ICS support for those baselines.

Comment 4

[Michael Vines [:m1] [:evilmachines]]

Our current focus is not on this baseline.

Comment 5

[Kartikaya Gupta (email:[e-mail])]

Pretty sure this is not going to get fixed at this point if it's buri-only.