> On Mon, Apr 17, 2023 at 7:53 PM Lorenzo Bianconi <lorenzo@xxxxxxxxxx> wrote: > > > > Hi all, > > > > I am triggering an issue with a device running the page_pool allocator. > > In particular, the device is running an iperf tcp server receiving traffic > > from a remote client. On the driver I loaded a simple xdp program returning > > xdp_pass. When I remove the ebpf program and destroy the pool, page_pool > > allocator starts complaining in page_pool_release_retry() that not all the pages > > have been returned to the allocator. In fact, the pool is not really destroyed > > in this case. > > Debugging the code it seems the pages are stuck softnet_data defer_list and > > they are never freed in skb_defer_free_flush() since I do not have any more tcp > > traffic. To prove it, I tried to set sysctl_skb_defer_max to 0 and the issue > > does not occur. > > I developed the poc patch below and the issue seems to be fixed: > > I do not see why this would be different than having buffers sitting > in some tcp receive > (or out or order) queues for a few minutes ? The main issue in my tests (and even in mt76 I think) is the pages are not returned to the pool for a very long time (even hours) and doing so the pool is like in a 'limbo' state where it is not actually deallocated and page_pool_release_retry continues complaining about it. I think this is because we do not have more tcp traffic to deallocate them, but I am not so familiar with tcp codebase :) Regards, Lorenzo > > Or buffers transferred to another socket or pipe (splice() and friends)
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