On Mon, Apr 10, 2023 at 02:06:27PM +0200, Kal Conley wrote: > diff --git a/Documentation/networking/af_xdp.rst b/Documentation/networking/af_xdp.rst > index 247c6c4127e9..ea65cd882af6 100644 > --- a/Documentation/networking/af_xdp.rst > +++ b/Documentation/networking/af_xdp.rst > @@ -105,12 +105,13 @@ with AF_XDP". It can be found at https://lwn.net/Articles/750845/. > UMEM > ---- > > -UMEM is a region of virtual contiguous memory, divided into > -equal-sized frames. An UMEM is associated to a netdev and a specific > -queue id of that netdev. It is created and configured (chunk size, > -headroom, start address and size) by using the XDP_UMEM_REG setsockopt > -system call. A UMEM is bound to a netdev and queue id, via the bind() > -system call. > +UMEM is a region of virtual contiguous memory divided into equal-sized > +frames. This is the area that contains all the buffers that packets can > +reside in. A UMEM is associated with a netdev and a specific queue id of > +that netdev. It is created and configured (start address, size, > +chunk size, and headroom) by using the XDP_UMEM_REG setsockopt system > +call. A UMEM is bound to a netdev and queue id via the bind() system > +call. > > An AF_XDP is socket linked to a single UMEM, but one UMEM can have > multiple AF_XDP sockets. To share an UMEM created via one socket A, > @@ -418,14 +419,21 @@ negatively impact performance. > XDP_UMEM_REG setsockopt > ----------------------- > > -This setsockopt registers a UMEM to a socket. This is the area that > -contain all the buffers that packet can reside in. The call takes a > -pointer to the beginning of this area and the size of it. Moreover, it > -also has parameter called chunk_size that is the size that the UMEM is > -divided into. It can only be 2K or 4K at the moment. If you have an > -UMEM area that is 128K and a chunk size of 2K, this means that you > -will be able to hold a maximum of 128K / 2K = 64 packets in your UMEM > -area and that your largest packet size can be 2K. > +This setsockopt registers a UMEM to a socket. The call takes a pointer > +to the beginning of this area and the size of it. Moreover, there is a > +parameter called chunk_size that is the size that the UMEM is divided > +into. The chunk size limits the maximum packet size that can be sent or > +received. For example, if you have a UMEM area that is 128K and a chunk > +size of 2K, then you will be able to hold a maximum of 128K / 2K = 64 > +packets in your UMEM. In this case, the maximum packet size will be 2K. > + > +Valid chunk sizes range from 2K to 64K. However, in aligned mode, the > +chunk size must also be a power of two. Additionally, the chunk size > +must not exceed the size of a page (usually 4K). This limitation is > +relaxed for UMEM areas allocated with HugeTLB pages, in which case > +chunk sizes up to 64K are allowed. Note, this only works with hugepages > +allocated from the kernel's persistent pool. Using Transparent Huge > +Pages (THP) has no effect on the maximum chunk size. > > There is also an option to set the headroom of each single buffer in > the UMEM. If you set this to N bytes, it means that the packet will The doc LGTM, thanks! For the doc part, Reviewed-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx> -- An old man doll... just what I always wanted! - Clara
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