David Schultz wrote: > > There's no chicken and egg problem when you're booting off install > > media or for that matter from single user mode. The problem was that > > softupdates means you don't get space back from deleted files immediatly > > so previously / tended to fillup during installworld or installkernel. > > I know some fixes have been implemented in that area, but I'm not sure > > if then mean you can always write to the space occupied by unlinked > > files or just that you have a better chance. > > The problem is effectively fixed in 5.0. Basically, when no space > can be found, the syncer is accelerated to try to speed up frees. > Technically it's possible to run into a livelock, where you keep > freeing space and it keeps getting snatched up before you can grab > it, so you wait forever. So IIRC, there is a point where it just > gives up on finding the space. However, that won't happen with an > install, so the free space problem isn't a reason not to use > softupdates on the root FS. I think the default hasn't been > changed just because nobody has bothered.
The easy way to fix this is to insert a new dependency for the completion of the allocation. Basically, this would put in a stall barrier that would cause the outstanding I/O to drain before the new I/O was attempted. All other operations behind the one that caused the stall would b held off, which would avoid the starvation deadlock you describe. Most likely, all this would require some minor code to maintain a running tally of virtual vs. real free block count. -- Terry To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-questions" in the body of the message
