Messages in this thread | | | Date | Sun, 2 Nov 2014 17:59:43 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC 0/2] drivers: spi/i2c: account completions as iowait |
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On Sun, Nov 02, 2014 at 02:58:07PM +0100, Wolfram Sang wrote:
> However, researching the net, users currently interpret iowait entirely as > blkio wait. Furthermore, io_schedule() calls delayacct_blkio_{start|end}() which > worked fine for my tests with I2C but might show that iowait was really meant as > blkiowait? So, should other subsystems use it?
I would tend to agree with that; historically this has always been about blkio, not device io.
> To make it more confusing, some people (like Peter Zijlstra [1]) seem to like > iowait gone, so maybe it is all not worth it?
Yeah, iowait accounting is terminally broken :-) Mostly because the iowait is accounted per-cpu but that is a very tenuous relation because the IO devices are not per IO and blocking tasks are not associated with any particular CPU -- after all they're not consuming CPU time.
If people really think its worth; we could invent new IO-wait measure that do make sense -- maybe, but the current thing is complete bollocks.
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