<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hello. <div class=""><br class=""></div><div class="">we have experience this problem many time, and we try many ways to solve this problem, but always failed.</div><div class=""><br class=""></div><div class="">such as sync && echo 3 > /proc/sys/vm/drop_caches to free more memory, however, after a while, the message come again.</div><div class=""><br class=""></div><div class="">the dmesg show:</div><div class=""><div class="">May 30 12:35:51 w-openstack21 kernel: XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)</div><div class="">May 30 12:35:53 w-openstack21 kernel: XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)</div><div class="">May 30 12:35:55 w-openstack21 kernel: XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)</div><div class="">May 30 12:35:57 w-openstack21 kernel: XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)</div><div class="">May 30 12:35:59 w-openstack21 kernel: XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)</div></div><div class=""><br class=""></div><div class="">our kernel version is 3.10.0-327.4.5.el7.x86_64</div><div class=""><br class=""></div><div class="">we think this is the kernel memory fragmentation problem, when dmesg show the error message, we check the buddyinfo</div><div class=""><br class=""></div><div class=""><div class="">[root@w-openstack21 /home/xusiliang]# cat /proc/buddyinfo</div><div class="">Node 0, zone DMA 1 0 1 0 2 1 1 0 1 1 3</div><div class="">Node 0, zone DMA32 2190 1898 1367 583 284 81 21 8 5 0 4</div><div class="">Node 0, zone Normal 85195 90572 56688 32379 16793 5568 930 230 184 11 0</div><div class="">Node 1, zone Normal 95799 127034 94363 49321 21555 5239 225 2 2 0 0</div></div><div class=""><br class=""></div><div class="">and I think the kernel have enough free memory</div><div class=""><div class="">[root@w-openstack21 /home/xusiliang]# free -m</div><div class=""> total used free shared buff/cache available</div><div class="">Mem: 64269 50357 11802 65 2109 11757</div><div class="">Swap: 32255 347 31908</div></div><div class=""><br class=""></div><div class="">This machine is running for qemu, the file is qemu qcow file type</div><div class=""><br class=""></div><div class=""><div class="">[root@w-openstack20 /data/nova/instances/7898b630-c4ef-49ab-9ce9-3735e090c282]# file disk</div><div class="">disk: QEMU QCOW Image (v3), has backing file (path /data/nova/instances/_base/3f27393376152ac352b2d85703011e38517e), 429496729600 bytes</div></div><div class=""><br class=""></div><div class="">we also use xfs_db to check the fragmentation</div><div class=""><br class=""></div><div class=""><div class="">[root@w-openstack20 /home/xusiliang]# xfs_db -r /dev/mapper/VolGroup00-LogVol04</div><div class="">xfs_db> frag</div><div class=""><br class=""></div><div class="">actual 48421430, ideal 20716, fragmentation factor 99.96%</div></div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">How can I solve this problem, what do you suggest me to do?</div><div class=""><br class=""></div><div class="">thank you</div><div class=""><br class=""></div><div class=""><br class=""><div class="">
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