On Wed, Aug 27, 2014 at 04:58:12PM +0200, Anshul Makkar wrote: > I am writing a block IO latency tracker. > > As obvious, I am calculating the latency by tracking the interval between > start of IO and end of IO. > (firing my latency tracker from function BlockDriverAIOCB *raw_aio_submit() > raw-posix.c when job is submitted). > > The latency data per QEMU process will be written to shared memory and then > another app uses this shared memory to read the data. That's a simple > architecture. > > Can't use "info blockstats" QMP command as qmp socket is used and blocked > by some other process in our subsystem. > > Just want a suggestion whether my approach is correct given the constraint > that I can't use qmp socket or if any alternative is possible.
Simplest option: use iostat(1) inside the guest. Or you can use tracing tools to measure block I/O request latency. An example from a few years ago: http://www.linux-kvm.org/page/Virtio/Block/Latency It depends what you are trying to achieve. Stefan
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