kern.ipc.shmmax limit or bug?

Fernando Schapachnik fernando at
Wed Aug 1 15:45:30 UTC 2007

Is there a limit on kern.ipc.shmmax on amd64?

Trying to set up 2GB:

machine# sysctl kern.ipc.shm_use_phys
kern.ipc.shm_use_phys: 1

machine# sysctl kern.ipc.shmmax=2147483648
kern.ipc.shmmax: 0 -> -2147483648

Trying 4GB:
machine# sysctl kern.ipc.shmmax=4294967296
kern.ipc.shmmax: -2147483648 -> 0

machine# dmesg|egrep "real|CPU"
CPU: Intel(R) Xeon(R) CPU            5160  @ 3.00GHz (2995.51-MHz K8-class CPU)
real memory  = 9395240960 (8960 MB)
FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs

machine# uname -a
FreeBSD machine 6.2-RELEASE FreeBSD 6.2-RELEASE #0: Fri Jan 12 08:43:30 UTC 2007     root at  amd64

Should I file a PR? If so, is there a workaround?


Fernando P. Schapachnik
fernando at

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