Re: [PATCH v4 3/9] sysctl: Make XEN_SYSCTL_topologyinfo sysctl a little more efficient

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 03/11/2015 07:04 AM, Ian Campbell wrote:
> On Mon, 2015-03-09 at 22:27 -0400, Boris Ostrovsky wrote:
>> Instead of copying data for each field in xen_sysctl_topologyinfo separately
>> put cpu/socket/node into a single structure and do a single copy for each
>> processor.
>>
>> Do not use max_cpu_index, which is almost always used for calculating number
>> CPUs (thus requiring adding or subtracting one), replace it with num_cpus.
>>
>> There is no need to copy whole op in sysctl to user at the end, we only need
>> num_cpus.
>>
>> Rename xen_sysctl_topologyinfo and XEN_SYSCTL_topologyinfo to reflect the fact
>> that these are used for CPU topology. Subsequent patch will add support for
>> PCI topology sysctl.
>>
>> Replace INVALID_TOPOLOGY_ID with "XEN_"-prefixed macros for each invalid type
>> (core, socket, node).
>>
>> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>> ---
>>
>> Changes in v4:
>> * Split v3's patch into two --- one for CPU topology and one for NUMA info
> I think this means this is now back to how v2 looked, in which case you
> may feel free to reinstate my ack. I only glanced through this version
> but it looks ok. Let me know if it is actually different to v2 and I'll
> have a closer look.


Yes, this is close to v2. The differences are that we are now sizing 
everything with max number of CPUs vs max CPU index (so a review for 
off-by-one errors would be useful) plus new INVALID macros that resulted 
in some (fairly minor) changes.

However, Andrew asked for more changes in sysctl implementation that may 
affect the interface (for both this and NUMA patches) so it's probably 
better to wait until v5.


-boris