Re: [Xen-devel] [PATCH v6] x86/mem-sharing: mem-sharing a range of memory

[Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>]

On Tue, Jul 12, 2016 at 1:17 AM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> On Mon, Jul 11, 2016 at 01:57:50PM -0600, Tamas K Lengyel wrote:
>> Currently mem-sharing can be performed on a page-by-page basis from the 
>> control
>> domain. However, this process is quite wasteful when a range of pages have to
>> be deduplicated.
>>
>> This patch introduces a new mem_sharing memop for range sharing where
>> the user doesn't have to separately nominate each page in both the source and
>> destination domain, and the looping over all pages happen in the hypervisor.
>> This significantly reduces the overhead of sharing a range of memory.
>>
>> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
>> ---
>> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
>> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
>> Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
>> Cc: Jan Beulich <jbeulich@xxxxxxxx>
>> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> ---
>>  tools/libxc/include/xenctrl.h        |  15 ++++
>>  tools/libxc/xc_memshr.c              |  19 +++++
>>  tools/tests/mem-sharing/memshrtool.c |  22 ++++++
>>  xen/arch/x86/mm/mem_sharing.c        | 140 
>> +++++++++++++++++++++++++++++++++++
>>  xen/include/public/memory.h          |  10 ++-
>>  5 files changed, 205 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
>> index 4a85b4a..650a763 100644
>> --- a/tools/libxc/include/xenctrl.h
>> +++ b/tools/libxc/include/xenctrl.h
>> @@ -2333,6 +2333,21 @@ int xc_memshr_add_to_physmap(xc_interface *xch,
>>                      domid_t client_domain,
>>                      unsigned long client_gfn);
>>
>> +/* Allows to deduplicate a range of memory of a client domain. Using
>> + * this function is equivalent of calling xc_memshr_nominate_gfn for each 
>> gfn
>> + * in the two domains followed by xc_memshr_share_gfns.
>> + *
>> + * May fail with -EINVAL if the source and client domain have different
>> + * memory size or if memory sharing is not enabled on either of the domains.
>> + * May also fail with -ENOMEM if there isn't enough memory available to 
>> store
>> + * the sharing metadata before deduplication can happen.
>> + */
>> +int xc_memshr_range_share(xc_interface *xch,
>> +                         domid_t source_domain,
>> +                         domid_t client_domain,
>> +                         unsigned long start,
>> +                         unsigned long end);
>
> Indentation seems wrong -- did you use tab here?

No, it's all spaces, but you are right, it was misaligned by a single space.

>
>> +
>>  /* Debug calls: return the number of pages referencing the shared frame 
>> backing
>>   * the input argument. Should be one or greater.
>>   *
>> diff --git a/tools/libxc/xc_memshr.c b/tools/libxc/xc_memshr.c
>> index deb0aa4..6b26f3f 100644
>> --- a/tools/libxc/xc_memshr.c
>> +++ b/tools/libxc/xc_memshr.c
>> @@ -181,6 +181,25 @@ int xc_memshr_add_to_physmap(xc_interface *xch,
>>      return xc_memshr_memop(xch, source_domain, &mso);
>>  }
>>
>> +int xc_memshr_range_share(xc_interface *xch,
>> +                         domid_t source_domain,
>> +                         domid_t client_domain,
>> +                         unsigned long start,
>> +                         unsigned long end)
>
> Ditto.
>
>> +{
>> +    xen_mem_sharing_op_t mso;
>> +
>> +    memset(&mso, 0, sizeof(mso));
>> +
>> +    mso.op = XENMEM_sharing_op_range_share;
>> +
>> +    mso.u.range.client_domain = client_domain;
>> +    mso.u.range.start = start;
>> +    mso.u.range.end = end;
>> +
>> +    return xc_memshr_memop(xch, source_domain, &mso);
>> +}
>> +
>>  int xc_memshr_domain_resume(xc_interface *xch,
>>                              domid_t domid)
>>  {
>> diff --git a/tools/tests/mem-sharing/memshrtool.c 
>> b/tools/tests/mem-sharing/memshrtool.c
>> index 437c7c9..bd1f4e0 100644
>> --- a/tools/tests/mem-sharing/memshrtool.c
>> +++ b/tools/tests/mem-sharing/memshrtool.c
>> @@ -24,6 +24,8 @@ static int usage(const char* prog)
>>      printf("  nominate <domid> <gfn>  - Nominate a page for sharing.\n");
>>      printf("  share <domid> <gfn> <handle> <source> <source-gfn> 
>> <source-handle>\n");
>>      printf("                          - Share two pages.\n");
>> +    printf("  range <source-domid> <destination-domid> <start-gfn> 
>> <end-gfn>\n");
>> +    printf("                          - Share pages between domains in 
>> range.\n");
>>      printf("  unshare <domid> <gfn>   - Unshare a page by grabbing a 
>> writable map.\n");
>>      printf("  add-to-physmap <domid> <gfn> <source> <source-gfn> 
>> <source-handle>\n");
>>      printf("                          - Populate a page in a domain with a 
>> shared page.\n");
>> @@ -180,6 +182,26 @@ int main(int argc, const char** argv)
>>          }
>>          printf("Audit returned %d errors.\n", rc);
>>      }
>> +    else if( !strcasecmp(cmd, "range") )
>> +    {
>> +        domid_t sdomid, cdomid;
>> +        int rc;
>> +        unsigned long start, end;
>> +
>> +        if( argc != 6 )
>
> Space after "if".
>
> With all those fixed:
>
> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

Thanks!
Tamas

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