Messages in this thread | | | Date | Mon, 3 Nov 2014 20:45:06 +0100 | From | Wolfram Sang <> | Subject | Re: [RFC 0/2] drivers: spi/i2c: account completions as iowait |
| |
> > 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 don't think so. The traditional Unix use of I/O wait is block I/O wait, > in order to account for paging/swapping in "uptime".
I see.
> The other problem is that if you change the way it behaves you'll get > lots of hate mail from people running server farms as all their load > balancing and cluster management changes behaviour, plus baffled users > wondering why their system is now busy and it wasn't in the last release.
I was fearing something like that. On the other hand, it might have been more correct. That's why I asked.
> The other question you have to solve is that people are adding i2c and > SPI slave support both in Android space and now perhaps upstream. How do > you I/O account those transactions ?
I implemented I2C slave support for upstream [1] and I don't think it needs to be acocunted. While a master transaction gets kicked off and then waits for success using a completion, slave support is more like serving an interrupt and then getting or putting a byte immediately.
Thanks for your answers, I'll simply keep I2C away from iowait.
Wolfram
[1] http://thread.gmane.org/gmane.linux.kernel/1783295
[unhandled content-type:application/pgp-signature]
| |