Severe instabilities and system lockups

Chuck Swiger cswiger at
Thu Mar 11 23:14:23 UTC 2010

On Mar 11, 2010, at 3:05 PM, David Jackson wrote:
[ ... ]
> I seem to have also discovered that the lockup problems are not entirely due to USB issues. Many of them were being caused by an apparent problem with the swap system. I have two swaps, a file backed swap and a partition swap on the same disk. Apparently when having two swaps on the disk there are severe performance problems. FreeBSD needs to fix whatever is causing this thrashing problem.

You're going to notice performance problems if you are paging heavily regardless of other factors.  And the fine documentation recommends placing only one swap partition per disk (or controller):

"On larger systems with multiple SCSI disks (or multiple IDE disks operating on different controllers), it is recommend that a swap is configured on each drive (up to four drives). The swap partitions should be approximately the same size. The kernel can handle arbitrary sizes but internal data structures scale to 4 times the largest swap partition. Keeping the swap partitions near the same size will allow the kernel to optimally stripe swap space across disks."

It might be reasonable for swapon to log or print a warning if it notices multiple swap partitions (or swapfiles) on the same underlying hardware device....


More information about the freebsd-questions mailing list