[dpdk-dev] [PATCH] net/vmxnet3: fix queue size changes

Charles (Chas) Williams ciwillia at brocade.com
Wed Mar 15 10:45:41 CET 2017



On 03/15/2017 04:18 AM, Jan Blunck wrote:
> On Tue, Mar 14, 2017 at 5:38 PM, Charles (Chas) Williams
> <ciwillia at brocade.com> wrote:
>>
>>
>> On 03/14/2017 12:11 PM, Jan Blunck wrote:
>>>
>>> On Mon, Mar 13, 2017 at 11:41 PM, Charles (Chas) Williams
>>> <ciwillia at brocade.com> wrote:
>>>>
>>>> If the user reconfigures the queues size, then the previosly allocated
>>>> memzone may potentially be too small.  Instead, always free the old
>>>> memzone and allocate a new one.
>>>>
>>>> Fixes: dfaff37fc46d ("vmxnet3: import new vmxnet3 poll mode driver
>>>> implementation")
>>>>
>>>> Signed-off-by: Chas Williams <ciwillia at brocade.com>
>>>> ---
>>>>  drivers/net/vmxnet3/vmxnet3_rxtx.c | 6 +++---
>>>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/net/vmxnet3/vmxnet3_rxtx.c
>>>> b/drivers/net/vmxnet3/vmxnet3_rxtx.c
>>>> index 6649c3f..104e040 100644
>>>> --- a/drivers/net/vmxnet3/vmxnet3_rxtx.c
>>>> +++ b/drivers/net/vmxnet3/vmxnet3_rxtx.c
>>>> @@ -893,8 +893,8 @@ vmxnet3_recv_pkts(void *rx_queue, struct rte_mbuf
>>>> **rx_pkts, uint16_t nb_pkts)
>>>>
>>>>  /*
>>>>   * Create memzone for device rings. malloc can't be used as the physical
>>>> address is
>>>> - * needed. If the memzone is already created, then this function returns
>>>> a ptr
>>>> - * to the old one.
>>>> + * needed. If the memzone already exists, we free it since it may have
>>>> been created
>>>> + * with a different size.
>>>>   */
>>>>  static const struct rte_memzone *
>>>>  ring_dma_zone_reserve(struct rte_eth_dev *dev, const char *ring_name,
>>>> @@ -909,7 +909,7 @@ ring_dma_zone_reserve(struct rte_eth_dev *dev, const
>>>> char *ring_name,
>>>>
>>>>         mz = rte_memzone_lookup(z_name);
>>>>         if (mz)
>>>> -               return mz;
>>>> +               rte_memzone_free(mz);
>>>>
>>>>         return rte_memzone_reserve_aligned(z_name, ring_size,
>>>>                                            socket_id, 0,
>>>> VMXNET3_RING_BA_ALIGN);
>>>
>>>
>>> Chas,
>>>
>>> Thanks for hunting this one down. Wouldn't the rte_memzone_free()
>>> better fit into vmxnet3_cmd_ring_release() ?
>>
>>
>> I don't care which way it goes.  I just did what is basically done in
>> gpa_zone_reserve() to match the "style".  Tracking the current ring size
>> and avoiding reallocating a potentially large chunk of memory seems like
>> a better idea.
>>
>>> Also the ring_dma_zone_reserve() could get replaced by
>>> rte_eth_dma_zone_reserve() (see also
>>
>>
>> Yes, it probably should get changed to that along with tracking the size.
>
> Why don't we always allocate VMXNET3_RX_RING_MAX_SIZE entries? That
> way we don't need to reallocate on a later queue setup change?

That's using more memory than it needs to use.  It might break someone's application
that already runs in some tightly constrained machine.  Failing to shrink the memzone
isn't likely to break anything since they have (apparently) already dealt with having
less memory available before switching to a smaller queue size.

Still, it can be a matter for another day.




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