<div dir="ltr"><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jan 26, 2016 at 2:01 PM, Andrei Perietanu <span dir="ltr"><<a href="mailto:andrei.perietanu@klastelecom.com" target="_blank">andrei.perietanu@klastelecom.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div><div class="h5"><br><div class="gmail_quote">On Tue, Jan 26, 2016 at 1:51 PM, Michal Privoznik <span dir="ltr"><<a href="mailto:mprivozn@redhat.com" target="_blank">mprivozn@redhat.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div><div>On 26.01.2016 14:35, Andrei Perietanu wrote:<br> > On Tue, Jan 26, 2016 at 12:39 PM, Michal Privoznik <<a href="mailto:mprivozn@redhat.com" target="_blank">mprivozn@redhat.com</a>><br> > wrote:<br> ><br> >> On 26.01.2016 12:30, Andrei Perietanu wrote:<br> >>> Hi all,<br> >>><br> >>> I am running KVM on a 3.18 kernel. The system runs and Atom processor<br> >> with<br> >>> 2Gb RAM.<br> >>><br> >>> Using KVM you obviously can over allocate your resources: say you have 4<br> >>> guests each configured with 1GB ram. Running all four at the same time,<br> >>> depending on the workload, can crash the system - I get a kernel trace<br> >> when<br> >>> this happens.<br> >>><br> >>> But let's consider a simpler case: one guest with 1.5 Gb RAM, ubuntu<br> >> 14.03.<br> >>> During the installation the system will again crash.<br> >>> The memory statistics (top or proc/meminfo) will show that the FreeMemory<br> >>> goes down to 12Mb when this happens - which kind of makes sense<br> >> considering<br> >>> the host will require some RAM to run.<br> >>><br> >>> But the question is: does libvirt offer any way to prevent this from<br> >>> happening?<br> >>><br> >>> Some way of not allowing the user to start a guest unless you have enough<br> >>> free memory. I know how much ram each guest has configured but that is<br> >> not<br> >>> enough. I need to know how much the system has available, and just<br> >> reading<br> >>> the free memory statistic does not help much since that is only a<br> >> snapshot<br> >>> - when running a guest you can have 1gb free now, and 10 mb free 2 min<br> >>> later.<br> >>><br> >>> Any ideas?<br> >><br> >> There is one option I see, use -mem-prealloc. Either you can passthrough<br> >> it onto qemu commandline [1] or use locked memoryBacking [2]. I advocate<br> >> for the latter though. Not only it will allocate all the memory at qemu<br> >> startup it will also lock it so it won't get swapped off.<br> >><br> >> Michal<br> >><br> >> 1: <a href="http://libvirt.org/drvqemu.html#qemucommand" rel="noreferrer" target="_blank">http://libvirt.org/drvqemu.html#qemucommand</a><br> >> 2: <a href="http://libvirt.org/formatdomain.html#elementsMemoryBacking" rel="noreferrer" target="_blank">http://libvirt.org/formatdomain.html#elementsMemoryBacking</a><br> >><br> ><br> > I tried memoryBacking: I added this to the domain xml:<br> > <memoryBacking><br> > <locked/><br> > </memoryBacking><br> ><br> > And got an error when attempting to start the vm: memory locking no<br> > supported by QEMU binary.<br> ><br> > Aside from that I don't really understand how this helps solve my issue -<br> > if you don't mind going a bit into details I'd appreciate it.<br> ><br> <br> </div></div>Well, it will make qemu to allocate all its memory on the start. So<br> either the allocation would be successful and domain will run or it<br> won't and qemu will die immediately.<br> <br> On the other hand, your kernel is heavily broken too. Instead of<br> crashing at OOM it should kill a process (usually the one that's<br> consuming the most memory => qemu in this case).<br> <span><font color="#888888"><br> Michal<br> </font></span></blockquote></div></div></div>Sorry, I said crashing; I meant it spits out a kernel trace. You can still use the system after it happens. I just want to prevent from happening in the first place.</div><span class=""><font color="#888888"><div class="gmail_extra"><br></div><div class="gmail_extra">Andrei</div></font></span></div></blockquote><div>In case it helps (maybe I didn't correctly diagnose the problem), this is how the kernel trace looks like:</div><div><br></div><div> Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371208] [<ffffffff81116389>] __get_free_pages+0x9/0x38</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371161] [<ffffffff8184cfdb>] dump_stack+0x49/0x5e</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371203] [<ffffffff8114be30>] alloc_pages_current+0xd1/0xda</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371299] [<ffffffff81005e35>] kvm_vcpu_ioctl+0x12e/0x4b4</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371145] ffff88004b5078e8 ffff88004b507803 ffff880000000015 0000000000000001</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371169] [<ffffffff811124e7>] dump_header+0x6d/0x1d4</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371251] [<ffffffff8102fc55>] ? vmx_invpcid_supported+0x1d/0x1d</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371239] [<ffffffff8102fc55>] ? vmx_invpcid_supported+0x1d/0x1d</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371288] [<ffffffff8109ba1d>] ? set_task_cpu+0x63/0xb4</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371195] [<ffffffff811176f8>] __alloc_pages_nodemask+0x6a0/0x812</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371312] [<ffffffff81096692>] ? check_preempt_curr+0x41/0x6f</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371139] ffff880044d06600 ffff88004b507918 ffffffff811124e7 ffff88004b507a08</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371183] [<ffffffff8123db16>] ? security_capable_noaudit+0x10/0x12</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371329] [<ffffffff81165cab>] SyS_ioctl+0x5b/0x7a</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371318] [<ffffffff81165c14>] do_vfs_ioctl+0x3e5/0x421</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371353] CPU 2: hi: 0, btch: 1 usd: 0</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371342] Node 0 DMA per-cpu:</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371306] [<ffffffff810964b7>] ? resched_curr+0x6e/0x70</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371274] [<ffffffff81016fdc>] kvm_arch_vcpu_ioctl_run+0xcbd/0xf59</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371245] [<ffffffff81033434>] handle_ept_violation+0x13d/0x149</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371356] CPU 3: hi: 0, btch: 1 usd: 0</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371256] [<ffffffff81036ffc>] vmx_handle_exit+0x80c/0x86f</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371335] [<ffffffff8184fff2>] system_call_fastpath+0x12/0x17</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371369] CPU 2: hi: 186, btch: 31 usd: 0</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371380] active_file:56 inactive_file:40 isolated_file:0</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371175] [<ffffffff811128c4>] oom_kill_process+0x77/0x328</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371339] Mem-Info:</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371346] CPU 0: hi: 0, btch: 1 usd: 0</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371389] Node 0 DMA free:7080kB min:44kB low:52kB high:64kB active_anon:7232kB inactive_anon:4kB active_file:0kB inactive_file:0kB unevictable:8kB isolated(anon):0kB isolated(file):0kB present:15980kB managed:15892kB mlocked:0kB dirty:12kB writeback:4kB mapped:0kB shmem:20kB slab_reclaimable:140kB slab_unreclaimable:112kB kernel_stack:0kB pagetables:44kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371400] lowmem_reserve[]: 0 1760 1760 1760</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371150] Call Trace:</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371406] Node 0 DMA32 free:5276kB min:5344kB low:6680kB high:8016kB active_anon:1549604kB inactive_anon:88kB active_file:224kB inactive_file:164kB unevictable:281088kB isolated(anon):0kB isolated(file):0kB present:1956104kB managed:1907836kB mlocked:0kB dirty:0kB writeback:0kB mapped:18864kB shmem:300kB slab_reclaimable:25736kB slab_unreclaimable:13268kB kernel_stack:1968kB pagetables:4940kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:2480 all_unreclaimable? yes</div><div><br></div><div>Message from syslogd@trx-r2 at Thu Jan 21 04:14:29 2010 ...</div><div>trx-r2 kernel: [ 6116.371293] [<ffffffff810153bd>] ? kvm_arch_vcpu_load+0xb0/0x183</div><div>.......</div></div>Andrei</div><div class="gmail_extra"><br></div></div> <br> <p><img src="http://www.klasonline.com/klas_telecom_email_sig_1_01.jpg"></p><p><span style="font-family:Arial;font-size:x-small">The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. 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