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Date: Fri, 10 Feb 2023 20:12:28 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: Magnus Karlsson <magnus.karlsson@...il.com>
Cc: netdev@...r.kernel.org,
Björn Töpel <bjorn@...nel.org>,
Magnus Karlsson <magnus.karlsson@...el.com>,
Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
Jonathan Lemon <jonathan.lemon@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>, bpf@...r.kernel.org,
kernel test robot <lkp@...el.com>
Subject: Re: [PATCH net-next v1] xsk: support use vaddr as ring
On Fri, 10 Feb 2023 10:52:20 +0100, Magnus Karlsson <magnus.karlsson@...il.com> wrote:
> On Fri, 10 Feb 2023 at 03:14, Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> >
> > When we try to start AF_XDP on some machines with long running time, due
> > to the machine's memory fragmentation problem, there is no sufficient
> > continuous physical memory that will cause the start failure.
> >
> > After AF_XDP fails to apply for continuous physical memory, this patch
> > tries to use vmalloc() to allocate memory to solve this problem.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > Reported-by: kernel test robot <lkp@...el.com>
> > Link: https://lore.kernel.org/oe-kbuild-all/202302091850.0HBmsDAq-lkp@intel.com
> > ---
> > net/xdp/xsk.c | 8 +++++---
> > net/xdp/xsk_queue.c | 21 +++++++++++++++------
> > net/xdp/xsk_queue.h | 1 +
> > 3 files changed, 21 insertions(+), 9 deletions(-)
> >
> > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> > index 9f0561b67c12..33db57548ee3 100644
> > --- a/net/xdp/xsk.c
> > +++ b/net/xdp/xsk.c
> > @@ -1296,7 +1296,6 @@ static int xsk_mmap(struct file *file, struct socket *sock,
> > struct xdp_sock *xs = xdp_sk(sock->sk);
> > struct xsk_queue *q = NULL;
> > unsigned long pfn;
> > - struct page *qpg;
> >
> > if (READ_ONCE(xs->state) != XSK_READY)
> > return -EBUSY;
> > @@ -1319,10 +1318,13 @@ static int xsk_mmap(struct file *file, struct socket *sock,
> >
> > /* Matches the smp_wmb() in xsk_init_queue */
> > smp_rmb();
> > - qpg = virt_to_head_page(q->ring);
> > - if (size > page_size(qpg))
> > +
> > + if (PAGE_ALIGN(q->ring_size) < size)
> > return -EINVAL;
> >
> > + if (is_vmalloc_addr(q->ring))
> > + return remap_vmalloc_range(vma, q->ring, 0);
> > +
> > pfn = virt_to_phys(q->ring) >> PAGE_SHIFT;
> > return remap_pfn_range(vma, vma->vm_start, pfn,
> > size, vma->vm_page_prot);
> > diff --git a/net/xdp/xsk_queue.c b/net/xdp/xsk_queue.c
> > index 6cf9586e5027..7b03102d1672 100644
> > --- a/net/xdp/xsk_queue.c
> > +++ b/net/xdp/xsk_queue.c
> > @@ -7,6 +7,7 @@
> > #include <linux/slab.h>
> > #include <linux/overflow.h>
> > #include <net/xdp_sock_drv.h>
> > +#include <linux/vmalloc.h>
> >
> > #include "xsk_queue.h"
> >
> > @@ -37,14 +38,18 @@ struct xsk_queue *xskq_create(u32 nentries, bool umem_queue)
> > __GFP_COMP | __GFP_NORETRY;
> > size = xskq_get_ring_size(q, umem_queue);
> >
> > + q->ring_size = size;
> > q->ring = (struct xdp_ring *)__get_free_pages(gfp_flags,
> > get_order(size));
> > - if (!q->ring) {
> > - kfree(q);
> > - return NULL;
> > - }
> > + if (q->ring)
> > + return q;
> > +
> > + q->ring = (struct xdp_ring *)vmalloc_user(size);
> > + if (q->ring)
> > + return q;
>
> Thanks for bringing this to attention. Interesting to see how hard it
> gets after a while to find consecutive memory since this is not a
> large area.
If the size of the queue is 8 * 1024, then the size of the desc[] is
8 * 1024 * 8 = 16 * PAGE, but we also add struct xdp_ring size, so it is
16page+. This is necessary to apply for a 4-order memory. If there are a
lot of queues, it is difficult.
Here, that we actually waste 15 pages. 4-Order memory is 32 pages, but we only
use 17 pages.
>
> I am wondering if it would be better to remove the __get_free_pages()
> and just go for vmalloc_user. There is no particular reason here for
> allocating consecutive physical pages for the ring. Does anyone see
> any problem with removing this? If not, please just remove
> __get_free_pages(), test it, and post a v2.
I agree.
Thanks.
>
> > - return q;
> > + kfree(q);
> > + return NULL;
> > }
> >
> > void xskq_destroy(struct xsk_queue *q)
> > @@ -52,6 +57,10 @@ void xskq_destroy(struct xsk_queue *q)
> > if (!q)
> > return;
> >
> > - page_frag_free(q->ring);
> > + if (is_vmalloc_addr(q->ring))
> > + vfree(q->ring);
> > + else
> > + page_frag_free(q->ring);
> > +
> > kfree(q);
> > }
> > diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
> > index c6fb6b763658..35922b8b92a8 100644
> > --- a/net/xdp/xsk_queue.h
> > +++ b/net/xdp/xsk_queue.h
> > @@ -45,6 +45,7 @@ struct xsk_queue {
> > struct xdp_ring *ring;
> > u64 invalid_descs;
> > u64 queue_empty_descs;
> > + size_t ring_size;
> > };
> >
> > /* The structure of the shared state of the rings are a simple
> > --
> > 2.32.0.3.g01195cf9f
> >
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