Re: [Qemu-devel] [PATCH 2/2] Add monitor command mem-nodes

[Wanlong Gao <gaowanlong@cn.fujitsu.com>]

On 06/05/2013 09:46 PM, Eduardo Habkost wrote:
> On Wed, Jun 05, 2013 at 11:58:25AM +0800, Wanlong Gao wrote:
>> Add monitor command mem-nodes to show the huge mapped
>> memory nodes locations.
>>
> 
> This is for machine consumption, so we need a QMP command.
> 
>> (qemu) info mem-nodes
>> /proc/14132/fd/13: 00002aaaaac00000-00002aaaeac00000: node0
>> /proc/14132/fd/13: 00002aaaeac00000-00002aab2ac00000: node1
>> /proc/14132/fd/14: 00002aab2ac00000-00002aab2b000000: node0
>> /proc/14132/fd/14: 00002aab2b000000-00002aab2b400000: node1
> 
> Are node0/node1 _host_ nodes?
> 
> How do I know what's the _guest_ address/node corresponding to each
> file/range above?
> 
> What I am really looking for is:
> 
>  * The correspondence between guest (virtual) NUMA nodes and guest
>    physical address ranges (it could be provided by the QMP version of
>    "info numa")

AFAIK, the guest NUMA nodes and guest physical address ranges are set
by seabios, we can't get this information from QEMU, and I think this
information is useless for pinning memory range to host.

>  * The correspondence between guest physical address ranges and ranges
>    inside the mapped files (so external tools could set the policy on
>    those files instead of requiring QEMU to set it directly)
> 
> I understand that your use case may require additional information and
> additional interfaces. But if we provide the information above we will
> allow external components set the policy on the hugetlbfs files before
> we add new interfaces required for your use case.

But the file backed memory is not good for the host which has many
virtual machines, in this situation, we can't handle anon THP yet.

And as I mentioned, the cross numa node access performance regression
is caused by pci-passthrough, it's a very long time bug, we should
back port the host memory pinning patch to old QEMU to resolve this performance
problem, too.

Thanks,
Wanlong Gao

> 
> Also, what about making it conditional to OSes where we really know
> "/proc/<pid>/fd/<fd>" is available?
> 
> 
>>
>> Refer to the proposal of Eduardo and Daniel.
>> http://article.gmane.org/gmane.comp.emulators.kvm.devel/93476
> 
>>
>> Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
>> ---
>>  monitor.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 45 insertions(+)
>>
>> diff --git a/monitor.c b/monitor.c
>> index eefc7f0..85c865f 100644
>> --- a/monitor.c
>> +++ b/monitor.c
>> @@ -74,6 +74,10 @@
>>  #endif
>>  #include "hw/lm32/lm32_pic.h"
>>  
>> +#if defined(CONFIG_NUMA)
>> +#include <numaif.h>
>> +#endif
>> +
>>  //#define DEBUG
>>  //#define DEBUG_COMPLETION
>>  
>> @@ -1759,6 +1763,38 @@ static void mem_info(Monitor *mon, const QDict *qdict)
>>  }
>>  #endif
>>  
>> +#if defined(CONFIG_NUMA)
>> +static void mem_nodes(Monitor *mon, const QDict *qdict)
>> +{
>> +    RAMBlock *block;
>> +    int prevnode, node;
>> +    unsigned long long c, start, area;
>> +    int fd;
>> +    int pid = getpid();
>> +    QTAILQ_FOREACH(block, &ram_list.blocks, next) {
>> +        if (!(fd = block->fd))
>> +            continue;
>> +        prevnode = -1;
>> +        start = 0;
>> +        area = (unsigned long long)block->host;
>> +        for (c = 0; c < block->length; c += TARGET_PAGE_SIZE) {
>> +            if (get_mempolicy(&node, NULL, 0, c + block->host,
>> +                              MPOL_F_ADDR | MPOL_F_NODE) < 0)
>> +                continue;
>> +            if (node == prevnode)
>> +                continue;
>> +            if (prevnode != -1)
>> +                monitor_printf(mon, "/proc/%d/fd/%d: %016Lx-%016Lx: node%d\n",
>> +                               pid, fd, start + area, c + area, prevnode);
>> +            prevnode = node;
>> +            start = c;
>> +         }
>> +         monitor_printf(mon, "/proc/%d/fd/%d: %016Lx-%016Lx: node%d\n",
>> +                        pid, fd, start + area, c + area, prevnode);
>> +    }
>> +}
>> +#endif
>> +
>>  #if defined(TARGET_SH4)
>>  
>>  static void print_tlb(Monitor *mon, int idx, tlb_t *tlb)
>> @@ -2567,6 +2603,15 @@ static mon_cmd_t info_cmds[] = {
>>          .mhandler.cmd = mem_info,
>>      },
>>  #endif
>> +#if defined(CONFIG_NUMA)
>> +    {
>> +        .name       = "mem-nodes",
>> +        .args_type  = "",
>> +        .params     = "",
>> +        .help       = "show the huge mapped memory nodes location",
>> +        .mhandler.cmd = mem_nodes,
>> +    },
>> +#endif
>>      {
>>          .name       = "mtree",
>>          .args_type  = "",
>> -- 
>> 1.8.3.rc2.10.g0c2b1cf
>>
>