On Thu, 19 Dec 2019 13:06:24 +0000 Neale Ferguson <ne...@sinenomine.net> wrote:
> And thus was born cio_ignore? Well, that was my second kernel patch :) (And the oldest one still existing in remnants -- /proc/subchannels only lived during the 2.4 era -- although the current cio_ignore implementation is a far cry from the original one.) The main problem cio_ignore was actually trying to solve were LPAR definitions including every device, their friends, and some random ones picked up on the street -- including devices shared with other LPARs. You don't want all of these, and especially you don't want to write to other people's disks by accident. > > > -------- Original message -------- > From: Ingo Adlung <adl...@de.ibm.com> > Date: 12/19/19 23:55 (GMT+10:00) > To: LINUX-390@VM.MARIST.EDU > Subject: Re: [LINUX-390] Happy birthday > > And I remember the legendary Install Fest parties we had with clients in > groups of 10-15 and eventually doing 1:1 calls. I wrote the I/O layer at > that time and was overwhelmed when people booted (IPLed) Linux into OS/390 > partitions with 10s of thousands of I/O devices defined/attached. In order > for not having to allocate so much static memory I first limited the number > of addressable devices to 1024, following the VSE/ESA model, and only when > clients wanted more (many did start with Linux in LPAR and only partitions > configured for OS/390 at hand) I back-ported dynamic boot memory allocation > back from the 2.3 kernel to 2.2, still avoiding large memory allocations > when all a client wanted to operate where just a handful of devices ... Ha, I thought 1024 devices would be enough for anybody :) Funnily enough, I ran into limitations of the procfs when I tried to create a /proc entry for every device discovered in 2.4. We only got per-device entries with the advent of sysfs (and the driver model) in 2.5. ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www2.marist.edu/htbin/wlvindex?LINUX-390
