> Incidently, looking at the PV entry angle for a moment. Suppose you > create a 1GB sysvshm (pageable) segment. That's 262144 pages. Mapping this > once means you consume 262144 PV entries. At 28 bytes each, that is > about 7.3MB of KVM. Now, fork this process 300 times. The numbers become > 78643200 PV entries taking up about 2.2GB of PV entries that would like to fit > in the 1G KVA space. We dont even nearly have a way to fit all this in. > > This is the killer reason for SHM_PHYS stuff. It avoids the PV load which > has to fit into a single confined space. The cost of the page table pages > sucks, but at least that is spread over the VM space of 300 processes.
Ok, I'm confused now - so I understood you to originally say that SHM does not eat into KVA regardless of whether I set the kern.ipc.shm_use_phys to '1' or not. This leads me to conclude that setting that sysctl to 1 will probably not be the magic bullet to stop my system from inexplicably halting. (my system with greatly (4x) increased SHM/SEM/etc. settings) But now in this post ... are you saying that from the "PV entry angle" that KVA _is_ sometimes used for SHM, when we create a pageable segment ? Or are you just providing a thought experiment and pointing out that if it _were_ done this way then XYZ bad things would occur ? thanks, PT To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
