Date: Mon, 17 Jun 2019 17:33:13 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 238670] [libkvm][patch] kvm_getswapinfo() returns swap device sizes too small incorrectly Message-ID: <bug-238670-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=238670 Bug ID: 238670 Summary: [libkvm][patch] kvm_getswapinfo() returns swap device sizes too small incorrectly Product: Base System Version: 12.0-RELEASE Hardware: Any OS: Any Status: New Severity: Affects Only Me Priority: --- Component: bin Assignee: bugs@FreeBSD.org Reporter: ota@j.email.ne.jp kvm_getswapinfo() function returns smaller device sizes than the actual swap device sizes configured available. "systat -swap" uses this API and shows problem. "sysctl -c" uses a different API and displays correct sizes. While "usesd" swap device sizes are reported correctly, when a swap device is used fully, it looks like system haven overwritten next partition. The root of problem is libkvm subtracts vm.dmmax, maximum VOP I/O allowed, form size of device erroneously. The following shows that 1 MB swap device is prepared, attached, and then fully used. Given FreeBSD swap skips 2 4k blocks, 1016 is the correct size available for swapping. # dd if=/dev/zero of=1MB bs=1M count=1 1+0 records in 1+0 records out 1048576 bytes transferred in 0.035823 secs (29271150 bytes/sec) # mdconfig -a -t vnode -f 1MB md0 # swapon /dev/md0 # swapctl -l Device: 1024-blocks Used: /dev/ada0s1b 2097144 0 /dev/md0 1016 0 # mount -t tmpfs tmpfs /mnt/tmp # dd if=/dev/zero of=/mnt/tmp/fill bs=1M count=2000 2000+0 records in 2000+0 records out 2097152000 bytes transferred in 36.267636 secs (57824337 bytes/sec) # swapctl -l Device: 1024-blocks Used: /dev/ada0s1b 2097144 144220 /dev/md0 1016 1016 # systat -swap Disk 1K-blocks Used /0% /10 /20 /30 /40 /50 /60 /70 /80 /90 /100 ada0s1b 2097016 144216 XXXX md0 888 1016 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XX 2097904 145232 XXXX -- You are receiving this mail because: You are the assignee for the bug.
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