Short waits with umwait
Short waits with umwait
Posted Jun 16, 2019 12:01 UTC (Sun) by caliloo (subscriber, #50055)In reply to: Short waits with umwait by ncm
Parent article: Short waits with umwait
Was thinking the same thing. Would be nice to have more details on the limitations of the memory range that can be specified (hopefully one cannot provide a -virtual I suppose- range that starts at 0x0 of length 2ˆ64 ... and how that instruction performs with DMA.
Posted Jun 17, 2019 2:48 UTC (Mon)
by ncm (guest, #165)
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Since Haswell, Intel already does fusion of two ALU instructions and two branches to one cycle -- on a good day, anyway; when I last checked, Clang was very bad at putting instructions in the right order to get this.
Short waits with umwait
It occurs to me that there is really no need for this instruction -- micro-op fusion ought to recognize a busy-wait loop, and translate it internally.