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From: | Alex-Uni |
Subject: | [Qemu-devel] Attempt for reproducible behavior |
Date: | Thu, 26 Feb 2009 13:44:15 +0100 |
User-agent: | Thunderbird 2.0.0.19 (Windows/20081209) |
Hello,I am trying to modify Qemu, so it offers reproducible behavior. I'm using the icounts for the time measurement.
For example:I have a simple code which measures the time before the start of a loop. The loop runs for an definite amount of rounds. In this case I let it count to 100000000 in a while-loop. Then the codes measures the time after the loop. Both times in milliseconds. The time difference is about 5000 milliseconds.
Now, while the loop is still running, i make a snapshot. Lets say at 2000 milliseconds. After loading this snapshot it the loop should run for 3000 milliseconds. But it doesnt, it's alway different.
I figured, that it depends on the value of next_tb and therefor on tcg_qemu_tb_exec(tc_ptr) in line 615 in the cpu-exec.c.
Now I have the problem, that I can't follow the code. I don't know why tcg_qemu_tb_exec(tc_ptr) produces different results
and where to look. I only found the define in the tcg.h. Can somebody help me with this problem? I'm working on the svn-version 5806. Thank you Alex (Please CC: me when replying, I am not on the list)
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