Re: Kernel 3.11 / 3.12 OOM killer and Xen ballooning

[James Dingwall <james.dingwall@zynstra.com>]

Bob Liu wrote:
> On 01/29/2014 01:15 AM, James Dingwall wrote:
>> Bob Liu wrote:
>>> I have made a patch by reserving extra 10% of original total memory, by
>>> this way I think we can make the system much more reliably in all cases.
>>> Could you please have a test? You don't need to set
>>> selfballoon_reserved_mb by yourself any more.
>> I have to say that with this patch the situation has definitely
>> improved.  I have been running it with 3.12.[78] and 3.13 and pushing it
>> quite hard for the last 10 days or so.  Unfortunately yesterday I got an
> Good news!
>
>> OOM during a compile (link) of webkit-gtk.  I think your patch is part
>> of the solution but I'm not sure if the other bit is simply to be more
>> generous with the guest memory allocation or something else.  Having
>> tested with memory = 512  and no tmem I get an OOM with the same
>> compile, with memory = 1024 and no tmem the compile completes ok (both
>> cases without maxmem).  As my domains are usually started with memory =
>> 512 and maxmem = 1024 it seems that there should be sufficient with my
> But I think from the beginning tmem/balloon driver can't expand guest
> memory from size 'memory' to 'maxmem' automatically.
I am carrying this patch for libxl (4.3.1) because maxmem wasn't being 
honoured.

diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 356f920..fb7965d 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -235,7 +235,7 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
      libxl_domain_set_nodeaffinity(ctx, domid, &info->nodemap);
      libxl_set_vcpuaffinity_all(ctx, domid, info->max_vcpus, 
&info->cpumap);

-    xc_domain_setmaxmem(ctx->xch, domid, info->target_memkb + 
LIBXL_MAXMEM_CONSTANT);
+    xc_domain_setmaxmem(ctx->xch, domid, info->max_memkb + 
LIBXL_MAXMEM_CONSTANT);
      xs_domid = xs_read(ctx->xsh, XBT_NULL, "/tool/xenstored/domid", NULL);
      state->store_domid = xs_domid ? atoi(xs_domid) : 0;
      free(xs_domid);

>
>> default parameters. Also for an experiment I set memory=1024 and removed
>> maxmem and when tmem is activated I see "[ 3393.884105] xen:balloon:
>> reserve_additional_memory: add_memory() failed: -17" printed many times
>> in the guest kernel log.
>>
> I'll take a look at it.
It seems possible that this could be the same cause as for the message 
being printed in dom0 and which I reported in 
http://lists.xen.org/archives/html/xen-devel/2012-12/msg01607.html and 
for which no fix seems to have made it to the kernel.  I'm still working 
around this with:

#!/bin/sh

CURRENT_KB="/sys/bus/xen_memory/devices/xen_memory0/info/current_kb"
TARGET_KB="/sys/bus/xen_memory/devices/xen_memory0/target_kb"

CKB=$(< "${CURRENT_KB}")
TKB=$(< "${TARGET_KB}")

if [ "${TKB}" -gt "${CKB}" ] ; then
         echo "Resizing dom0 memory balloon target to ${CKB}"
         echo "${CKB}" > "${TARGET_KB}"
fi

Thanks,
James


-- 

*James Dingwall*

Script Monkey

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