Re: [PATCH v1 04/24] vfio-user: add region cache

[John Johnson]

> On Dec 12, 2022, at 3:42 AM, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
> 
> On 9/11/22 00:13, John Johnson wrote:
>> cache VFIO_DEVICE_GET_REGION_INFO results to reduce
>> memory alloc/free cycles and as prep work for vfio-user
>> Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
>> Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
>> Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
>> ---
>>  hw/vfio/ccw.c                 |  5 -----
>>  hw/vfio/common.c              | 41 +++++++++++++++++++++++++++++++++++------
>>  hw/vfio/igd.c                 | 23 +++++++++--------------
>>  hw/vfio/migration.c           |  2 --
>>  hw/vfio/pci-quirks.c          | 19 +++++--------------
>>  hw/vfio/pci.c                 |  8 --------
>>  include/hw/vfio/vfio-common.h |  2 ++
>>  7 files changed, 51 insertions(+), 49 deletions(-)
> 
> 
>>  void vfio_put_base_device(VFIODevice *vbasedev)
>>  {
>> +    if (vbasedev->regions != NULL) {
>> +        int i;
>> +
>> +        for (i = 0; i < vbasedev->num_regions; i++) {
>> +            g_free(vbasedev->regions[i]);
>> +        }
>> +        g_free(vbasedev->regions);
>> +        vbasedev->regions = NULL;
>> +    }
>> +
>>      if (!vbasedev->group) {
>>          return;
>>      }
>> @@ -2432,6 +2451,17 @@ int vfio_get_region_info(VFIODevice *vbasedev, int 
>> index,
>>  {
>>      size_t argsz = sizeof(struct vfio_region_info);
>>  +    /* create region cache */
>> +    if (vbasedev->regions == NULL) {
>> +        vbasedev->regions = g_new0(struct vfio_region_info *,
>> +                                   vbasedev->num_regions);
>> +    }
>> +    /* check cache */
>> +    if (vbasedev->regions[index] != NULL) {
>> +        *info = vbasedev->regions[index];
>> +        return 0;
>> +    }
> 
> What about simply allocating/releasing once regions[] in
> vfio_instance_init / vfio_instance_finalize?


        I think this is done already, except with _realize and 
_instance_finalize.

e.g,, vfio_realize() -> vfio_get_device() -> vfio_get_all_regions  allocates

and

vfio_instance_finalize -> vfio_put_device -> vfio_put_base_device  deallocates

                                                                JJ