On 28 December 2011 00:43, Xin Tong <xerox.time.t...@gmail.com> wrote: > Which version of QEMU did you do your test on, and what are the tests.
It was whatever trunk qemu was a year or so ago, and the test was just "time to login prompt for ARM guest in system mode". > I modified QEMU to check for interrupt status at the end of every TB > and ran it on SPECINT2000 benchmarks with QEMU 0.15.0. The performance > is 70% of the unmodified one for some benchmarks on a x86_64 host. I don't suppose you could provide a brief set of instructions for setting up a benchmark setup like this? (Is this user-mode or system-mode?) > I > agree that the extra load-test-branch-not-taken per TB is minimal, but > what I found is that the average number of TB executed per TB enter is > low (~3.5 TBs), while the unmodified approach has ~10 TBs per TB > enter. this makes me wonder why. Maybe the mechanism i used to gather > this statistics is flawed. but the performance is indeed hindered. Odd. > By keeping a counter that decrements on every TB, and when the counter > reaches 0, the current executing TB checks for interrupt status. Decrementing a counter on every TB is going to be slower than just checking a flag, so you might as well just check the flag. (If the flag is set you need to handle the interrupt anyway so there's no point delaying it.) -- PMM
