[EMAIL PROTECTED] wrote: > This patch introduces another rttesting driver, xeno_irqbench, for > measuring external IRQ latencies. The irqbench device is controlled > by a user-mode tool irqloop. A second tool for plain Linux, irqbench, > is provided to trigger the event over serial or parallel cross-link > (the latter is incomplete yet) and measure the reaction latency. >
As a follow-up, here is a patch to add some documentation for irqbench. I do not repeat the command line args of irqbench/irqloop, but feel free to point out missing explanations. Jan
Index: xenomai/doc/txt/irqbench.txt =================================================================== --- /dev/null +++ xenomai/doc/txt/irqbench.txt @@ -0,0 +1,48 @@ +IRQ Latency Benchmark +--------------------- + +This latency benchmark for external interrupts consists of three parts: + +1. xeno_irqbench (ksrc/drivers/testing) + RTDM driver for the test target to handle and reply to the IRQ events, or + forward them to user-space. + +2. irqloop (src/testsuite/irqbench) + xeno_irqbench control front-end and user-space loop-closer. Runs against + the POSIX skin on the test target. + +3. irqbench (src/testsuite/irqbench) + IRQ triggering and reaction measuring tool for the log system. Runs over + plain Linux on x86 hosts (contains inline assembly, ports to other archs + will be welcome). + +To link both test and log system, a null-modem cable between 8250-compatible +two RS232 ports is required. The infrastructure for parallel port cross-over +is prepared as well, but yet untested and incomplete. The null-modem cable +must provide at least the following links: + + test target log system + ----------- ---------- + CTS(8) <------ RTS(7) IRQ trigger + RTS(7) ------> CTS(8) reply + + DCD(1) + and/or <------ DTR(4) trace trigger (optional) + DSR(6) + + (Pin number on 9-pin sub-D socket) + +Test and log system can be started in arbitrary order, they will wait on +each other. + +The log system runs each single IRQ measurement with local IRQs disabled. It +will wait up to 100 times the current period on the test system's reply (after +initial successful synchronisation, which happens with IRQs enabled). Note that +these timeouts may disturb other processes or drivers on the log system. + +Keep in mind for test evaluations that, by design, irqbench will not trigger a +new IRQ event before the reply on the previous one has arrived or timed out. +Thus the specified test period may be dynamically expended in case of +overload. But maximum a latency close or above the period will clearly +indicate this. + Index: xenomai/doc/txt/Makefile.am =================================================================== --- xenomai.orig/doc/txt/Makefile.am +++ xenomai/doc/txt/Makefile.am @@ -2,6 +2,7 @@ txtdocdir = $(datadir)/doc/$(PACKAGE)-$( dist_txtdoc_DATA = \ 16550A-driver.txt \ + irqbench.txt \ pse51-skin.txt \ psos-skin.txt \ rtai-skin.txt \
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