554584 - Frequent calls to _semwait_signal cause Minefield to constantly use some CPU

Status: RESOLVED FIXED

(Firefox :: General, defect)

Description

[Bryan Blackburn]

User-Agent:       Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.3a4pre) Gecko/20100323 Minefield/3.7a4pre
Build Identifier: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.3a4pre) Gecko/20100323 Minefield/3.7a4pre

Noticed that after Minefield has finished all launching duties that it was continuing to take CPU (though not major, but about 3% or more), even with about:blank being the only page open.  A dtruss against the process shows a bunch of:

__semwait_signal(0x2703, 0x7C03, 0x1)		 = 0 0
__semwait_signal(0x2703, 0x7C03, 0x1)		 = -1 Err#60
__semwait_signal(0x7C03, 0x2703, 0x1)		 = 0 0
__semwait_signal(0x7C03, 0x2703, 0x1)		 = -1 Err#60
__semwait_signal(0x2703, 0x7C03, 0x1)		 = 0 0
__semwait_signal(0x2703, 0x7C03, 0x1)		 = 0 0
__semwait_signal(0x2703, 0x7C03, 0x1)		 = -1 Err#60
__semwait_signal(0x7C03, 0x2703, 0x1)		 = 0 0
__semwait_signal(0x7C03, 0x2703, 0x1)		 = -1 Err#60

going constantly; a sample output will also be attached.

Reproducible: Always

Steps to Reproduce:
1.  Launch Minefield with only about:blank loaded
2.  Wait for various startup bits to be done (talking to fontd seems to be the last bits, so once that disappears from processes using CPU, should be ready)
3.  firefix-bin should still be using CPU
Actual Results:  
CPU usage continues without any pages (except about:blank) loaded.

Expected Results:  
CPU usage usually should be 0%.

My previous nightly is definitely older (3.7a2pre 20100224) but has much better CPU usage.

Comment 1

[Bryan Blackburn]

Attachment: Sampling of Minefield using CPU for blank page

Comment 2

[Nickolay_Ponomarev]

The nightly you reported this with had bug 463695's fix in it, I think that was the reason of extensive cpu usage you noticed. (BTW, using https://developer.mozilla.org/en/DTrace would let you get a better diagnostics for the reason behind the CPU usage).

It should be much better in current nightlies (after bug 586216's fix).