Pavel Dovgalyuk <dovga...@ispras.ru> writes: > I also encountered icount problems with new MTTCG patches. > > Record/replay now cannot work, because iothread requests timers > without kicking the CPU. And cpu thread updates icount (that > are used for the clock).
The interaction of kicking the vCPU while grabbing the BQL was a side-effect. This is now done explicitly for single-threaded emulation by (6546706d28): tcg: add kick timer for single-threaded vCPU emulation > Therefore invocation of iothread uses incorrect clock and > all virtual timers behave incorrectly. > > Record/replay is also broken because current icount is requested > from iothread where current_cpu (and icount progress stored in icount_extra) > is unavailable. I'm working through Paolo's series now but I don't see it as insurmountable. The aim of keeping current_cpu set only during the cpu-exec loop was intentional because the system as a whole can't make assumptions about it always being valid. > > Pavel Dovgalyuk > >> -----Original Message----- >> From: mttcg-requ...@listserver.greensocs.com >> [mailto:mttcg-requ...@listserver.greensocs.com] >> On Behalf Of Nutaro, James J. >> Sent: Friday, March 03, 2017 10:39 PM >> To: 'mt...@listserver.greensocs.com' >> Cc: 'qemu-devel@nongnu.org' >> Subject: RE: -rtc clock=vm with -icount 1,sleep=off introduces unexpected >> delays in device >> interactions >> >> My original problem seems to stem from something that changed in the way >> that device emulation >> and instruction execution interact (I'm guessing). To reproduce the issue, I >> started a linux >> image with >> >> qemu-system-i386 -rtc clock=vm -monitor none -icount 1,sleep=off jack.img >> >> After booting, I run >> >> ping localhost >> >> The first round trip time reports look reasonable, being in the millisecond >> to sub-millisecond >> range. These occur while the emulator is running slower than real time. >> >> After a bit, the emulator speeds up (skipping over idle periods during I/O?) >> and the round >> trip times jump to hundreds of milliseconds, which I had not expected. >> >> If you want to try this experiment yourself, you can get the disk image that >> I used from here: >> >> http://www.ornl.gov/~1qn/qemu-images/jack.img >> >> >> Jim -- Alex Bennée
