Date: Mon, 13 Mar 2000 12:41:08 +0100 From: Gary Jennejohn <garyj@peedub.muc.de> To: Patryk Zadarnowski <patrykz@ilion.eu.org> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: 5.0 features? Message-ID: <200003131141.MAA79158@peedub.muc.de> In-Reply-To: Your message of "Mon, 13 Mar 2000 11:06:26 %2B1100." <200003130006.LAA05238@mycenae.ilion.eu.org>
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Patryk Zadarnowski writes: >> Mark Hittinger writes: >> > >> >Something that the old DEC took a few stabs at was the idea of a >> >"checkpoint" feature where a process or a series of processes could be >> >put in a quiesced state. This would page out the process or processes >> >into the swap space, allow a hardware shutdown, and after a reboot allow >> >the restart of the checkpointed process(es). >> > >> >> I did something like this for Philips while I was at UniSoft. It >> depended on some special hardware features (turning off/losing power >> generated an interrupt, there was a small UPS in the box along with >> battery-backed SRAM to save various kernel structures). >> >> Turning off the power caused all memory to be saved to disk (the kernel >> turned off the UPS after it was done). Upon a restart the kernel noticed >> that memory had been saved, read the contents in from disk, futzed around >> with some structures, and restarted what was curproc at the time of >> shutdown. It even worked ;-) >> >> Philips never did anything with it. > >Out of pure curiosity, what did you do with pending interrupts, partially >completed DMA transfers and other such state information? > IIRC (this was all 13 years ago) there were hooks in the drivers which were called on shutdown/startup so that they could DTRT. I do remeber that some characters were lost on the serial ports. Disk and network seemed to work fine, though. --- Gary Jennejohn / garyj@muc.de garyj@fkr.cpqcorp.net gj@freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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