![]() Only a minority of instructions flush the instructionĭecode (and hence TCG translation) buffers, though for Typically associated with cache management, system callsĪnd/or thread switching also act as barriers.Ħ. Some specific operations (see the architecture manuals) ![]() Synchronization between the CPU and FPU chips withinĥ. To any point up to and including the next same-CPU WAIT,īut this was never a multi-CPU barrier, just Point instructions might postpone their memory writes "FPU disabled" exception), (on 386 and older, floating "WAIT" opcode is now a NOP (optionally throwing an On modern CPUs, the floating point ("ESC") instructionsĪre treated as normal instructions, the related historic Some of the XCHG-family instructions implicitly behaveĤ. Explicit memory barrier instructions (there have beenģ. On a single address, then another memory barrier.Ģ. Require a memory barrier, then a locked read-modify-write Instructions with the explicit "LOCK" prefix, these Implemented on modern machines with multiple actual x86ĬPU sockets, as opposed to multicore chips, it may alsoīe observed when using any kind of DMA/bus-masterġ. The x86 memory model would require barriers everywhereĪnd it's not clear it would overall improve performance.ĪRM-on-x86 is the primary initial usecase.)įor your information, the x86 memory model only requiresīarriers in the following cases (this is somewhat With multiple cpus might not ever be supported because Make better use of multi-core hosts but it's not veryįar advanced yet. There is some development work in progress to try to (We do have some helper threads for aįew IO tasks etc but those are not cpu-bound.) Our current emulation is single threadedĮven when emulating multiple target CPUs, so we'll only Qemu, top only shows one qemu-system-i386 using 100% of one core I built qemu with -target-list i386-softmmu and when I run On 3 January 2016 at 20:57, David Durham wrote:Īny suggestions or comments on how to do this are very welcome
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