This is based on the procedure described here. If it is necessary to increase the size of the KVM guest physical volume first, and the KVM physical disk has no space remaining, use the procedure here to resize the KVM disk first, then follow this procedure to increase the size of the swap volume. The procedure increases the swap logical volume by 3G.
[root@oracle631 ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/vda2 vg_oracle631 lvm2 a-- 19.51g 0
/dev/vdb vg_u00 lvm2 a-- 20.00g 0
[root@oracle631 ~]# pvresize /dev/vda2
Physical volume "/dev/vda2" changed
1 physical volume(s) resized / 0 physical volume(s) not resized
[root@oracle631 ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/vda2 vg_oracle631 lvm2 a-- 29.51g 10.00g
/dev/vdb vg_u00 lvm2 a-- 20.00g 0
[root@oracle631 ~]# vgs
VG #PV #LV #SN Attr VSize VFree
vg_oracle631 1 2 0 wz--n- 29.51g 10.00g
vg_u00 1 1 0 wz--n- 20.00g 0
[root@oracle631 ~]# lvdisplay <-- swap logical volume shown below only for brevity
--- Logical volume ---
LV Path /dev/vg_oracle631/lv_swap
LV Name lv_swap
VG Name vg_oracle631
LV UUID v8X0vf-Hvwm-S9Pk-8GTh-NtXL-8Agg-vAgVMi
LV Write Access read/write
LV Creation host, time oracle631.vmem.org, 2014-08-10 13:47:48 -0500
LV Status available
# open 2
LV Size 1.97 GiB
Current LE 504
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 252:1
[root@oracle631 ~]# lvm lvresize /dev/vg_oracle631/lv_swap -L +3072M
Extending logical volume lv_swap to 4.97 GiB
Logical volume lv_swap successfully resized
[root@oracle631 ~]# mkswap /dev/vg_oracle631/lv_swap
mkswap: /dev/vg_oracle631/lv_swap: warning: don't erase bootbits sectors
on whole disk. Use -f to force.
Setting up swapspace version 1, size = 5210108 KiB
no label, UUID=e1aed1a3-7025-4058-84fd-c5bdc0cd043f
[root@oracle631 ~]# swapon -va
swapon on /dev/mapper/vg_oracle631-lv_swap
swapon: /dev/mapper/vg_oracle631-lv_swap: found swap signature: version 1, page-size 4, same byte order
swapon: /dev/mapper/vg_oracle631-lv_swap: pagesize=4096, swapsize=5335154688, devsize=5335154688
[root@oracle631 ~]# free -m
total used free shared buffers cached
Mem: 4961 298 4663 0 24 100
-/+ buffers/cache: 173 4788
Swap: 5087 0 5087
[root@oracle631 ~]#