Re: Socket recv behaviour in real-time context
Re: Socket recv behaviour in real-time context
- Subject: Re: Socket recv behaviour in real-time context
- From: Jeff Moore <email@hidden>
- Date: Sun, 15 Mar 2009 12:28:59 -0700
Basically, 50 milliseconds of latency means that your thread is not
running when you think it should be running. You'll want to use tools
that let you take a look at the scheduler activity. This means using
tools like the system trace profile in Shark or just plain old kernel
tracing.
You'll probably also want to find tools that can help you correlate
the thread activity with what's going on with the networking side of
things. Shark may help you a bit with that, since I'm sure there are
probably a few system calls involved with networking.
On Mar 15, 2009, at 12:16 PM, Stéphane Letz wrote:
Message: 1
Date: Sat, 14 Mar 2009 17:45:46 -0700
From: Jeff Moore <email@hidden>
Subject: Re: Socket recv behaviour in real-time context
To: CoreAudio API <email@hidden>
Message-ID: <email@hidden>
Content-Type: text/plain; charset=iso-8859-1; format=flowed;
delsp=yes
I don't really know a whole lot about sockets or our network stack.
But, your description of the problem sounds like there could be a
priority inversion problem on your slave machine. Even though the
thread you have servicing the socket is a real time thread, I'd bet
good money that the thread in the kernel that feeds the socket is
not.
This means that the more activity you have in your real time threads
(including the HAL's IO thread or any MIDI threads) will cause
scheduling latency for lower priority threads.
That said, 50 milliseconds seems completely crazy. You'd have to have
an awful lot of real time threads doing work to get that kind of
scheduling latency. Have you gotten any kernel traces?
On Mar 13, 2009, at 10:30 AM, Stéphane Letz wrote:
What kind of tools can be used in this case?
--
Jeff Moore
Core Audio
Apple
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