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[Qemu-devel] Tracing concerns for concurrent execution


From: Prerna Saxena
Subject: [Qemu-devel] Tracing concerns for concurrent execution
Date: Wed, 26 May 2010 11:32:31 +0530
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Hi,
I am writing a tracing back-end that logs tracepoint-based traces to qemu-internal global buffers. I had zeroed in on a lockless buffer for logging traces(to prevent slowdowns 'cos of locks held while tracing). However, I'm not sure if qemu threads might need some synchronisation to access the global trace buffer. I think the vcpu threads run lock-step, but this lock-step behaviour is not guaranteed for some other types of threads, such as the aio helper threads ? Also, can there be concurrency issues while tracing dynamic translator ? While I'm doing my study, it would be good to have some pointers on what assumptions can / not be made for concurrent thread execution in qemu, and what could be done to safeguard tracing in such hot-paths ?

Regards,
--
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India



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