linux-kernel - Re: [PATCH v2] virtio_ring: use alloc_pages

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Date:   Mon, 27 Jul 2020 21:10:09 +0800
From:   Shile Zhang <shile.zhang@...ux.alibaba.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Jiang Liu <liuj97@...il.com>, linux-pci@...r.kernel.org,
        bhelgaas@...gle.com
Subject: Re: [PATCH v2] virtio_ring: use alloc_pages_node for NUMA-aware
 allocation



On 2020/7/21 19:28, Shile Zhang wrote:
> 
> 
> On 2020/7/21 16:18, Michael S. Tsirkin wrote:
>> On Tue, Jul 21, 2020 at 03:00:13PM +0800, Shile Zhang wrote:
>>> Use alloc_pages_node() allocate memory for vring queue with proper
>>> NUMA affinity.
>>>
>>> Reported-by: kernel test robot <lkp@...el.com>
>>> Suggested-by: Jiang Liu <liuj97@...il.com>
>>> Signed-off-by: Shile Zhang <shile.zhang@...ux.alibaba.com>
>>
>> Do you observe any performance gains from this patch?
> 
> Thanks for your comments!
> Yes, the bandwidth can boost more than doubled (from 30Gbps to 80GBps) 
> with this changes in my test env (8 numa nodes), with netperf test.
> 
>>
>> I also wonder why isn't the probe code run on the correct numa node?
>> That would fix a wide class of issues like this without need to tweak
>> drivers.
> 
> Good point, I'll check this, thanks!

Sorry, I have no idea about how the probe code to grab the appropriate 
NUMA node.

> 
>>
>> Bjorn, what do you think? Was this considered?

Hi Bjorn, Could you please give any comments about this issue?
Thanks!

>>
>>> ---
>>> Changelog
>>> v1 -> v2:
>>> - fixed compile warning reported by LKP.
>>> ---
>>>   drivers/virtio/virtio_ring.c | 10 ++++++----
>>>   1 file changed, 6 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
>>> index 58b96baa8d48..d38fd6872c8c 100644
>>> --- a/drivers/virtio/virtio_ring.c
>>> +++ b/drivers/virtio/virtio_ring.c
>>> @@ -276,9 +276,11 @@ static void *vring_alloc_queue(struct 
>>> virtio_device *vdev, size_t size,
>>>           return dma_alloc_coherent(vdev->dev.parent, size,
>>>                         dma_handle, flag);
>>>       } else {
>>> -        void *queue = alloc_pages_exact(PAGE_ALIGN(size), flag);
>>> -
>>> -        if (queue) {
>>> +        void *queue = NULL;
>>> +        struct page *page = 
>>> alloc_pages_node(dev_to_node(vdev->dev.parent),
>>> +                             flag, get_order(size));
>>> +        if (page) {
>>> +            queue = page_address(page);
>>>               phys_addr_t phys_addr = virt_to_phys(queue);
>>>               *dma_handle = (dma_addr_t)phys_addr;
>>> @@ -308,7 +310,7 @@ static void vring_free_queue(struct virtio_device 
>>> *vdev, size_t size,
>>>       if (vring_use_dma_api(vdev))
>>>           dma_free_coherent(vdev->dev.parent, size, queue, dma_handle);
>>>       else
>>> -        free_pages_exact(queue, PAGE_ALIGN(size));
>>> +        free_pages((unsigned long)queue, get_order(size));
>>>   }
>>>   /*
>>> -- 
>>> 2.24.0.rc2