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Message-ID: <CAJ8uoz0Ayfbtf0ENciXoJxmzQUk4tHL58v3QWPdWmc01Y7Pz=A@mail.gmail.com>
Date: Fri, 10 Feb 2023 15:27:08 +0100
From: Magnus Karlsson <magnus.karlsson@...il.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.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 at 13:21, Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> 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.
One more good argument to stop using __get_free_pages() in this function.
> >
> > 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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