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Date: Fri, 31 Aug 2018 10:34:56 +0200
From: Björn Töpel <bjorn.topel@...el.com>
To: Jakub Kicinski <jakub.kicinski@...ronome.com>,
Björn Töpel <bjorn.topel@...il.com>
Cc: magnus.karlsson@...el.com, magnus.karlsson@...il.com,
alexander.h.duyck@...el.com, alexander.duyck@...il.com,
ast@...nel.org, brouer@...hat.com, daniel@...earbox.net,
netdev@...r.kernel.org, jesse.brandeburg@...el.com,
anjali.singhai@...el.com, peter.waskiewicz.jr@...el.com,
michael.lundkvist@...csson.com, willemdebruijn.kernel@...il.com,
john.fastabend@...il.com, neerav.parikh@...el.com,
mykyta.iziumtsev@...aro.org, francois.ozog@...aro.org,
ilias.apalodimas@...aro.org, brian.brooks@...aro.org,
u9012063@...il.com, pavel@...tnetmon.com, qi.z.zhang@...el.com
Subject: Re: [RFC] net: xsk: add a simple buffer reuse queue
On 2018-08-29 21:19, Jakub Kicinski wrote:
> XSK UMEM is strongly single producer single consumer so reuse of
> frames is challenging. Add a simple "stash" of FILL packets to
> reuse for drivers to optionally make use of. This is useful
> when driver has to free (ndo_stop) or resize a ring with an active
> AF_XDP ZC socket.
>
I'll take a stab using this in i40e. I have a couple of
comments/thoughts on this RFC, but let me get back when I have an actual
patch in place. :-)
Thanks!
Björn
> Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
> ---
> include/net/xdp_sock.h | 44 +++++++++++++++++++++++++++++++++
> net/xdp/xdp_umem.c | 2 ++
> net/xdp/xsk_queue.c | 56 ++++++++++++++++++++++++++++++++++++++++++
> net/xdp/xsk_queue.h | 3 +++
> 4 files changed, 105 insertions(+)
>
> diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
> index 6871e4755975..108c1c100de4 100644
> --- a/include/net/xdp_sock.h
> +++ b/include/net/xdp_sock.h
> @@ -14,6 +14,7 @@
> #include <net/sock.h>
>
> struct net_device;
> +struct xdp_umem_fq_reuse;
> struct xsk_queue;
>
> struct xdp_umem_props {
> @@ -41,6 +42,7 @@ struct xdp_umem {
> struct page **pgs;
> u32 npgs;
> struct net_device *dev;
> + struct xdp_umem_fq_reuse *fq_reuse;
> u16 queue_id;
> bool zc;
> spinlock_t xsk_list_lock;
> @@ -110,4 +112,46 @@ static inline dma_addr_t xdp_umem_get_dma(struct xdp_umem *umem, u64 addr)
> return umem->pages[addr >> PAGE_SHIFT].dma + (addr & (PAGE_SIZE - 1));
> }
>
> +struct xdp_umem_fq_reuse {
> + u32 nentries;
> + u32 length;
> + u64 handles[];
> +};
> +
> +/* Following functions are not thread-safe in any way */
> +struct xdp_umem_fq_reuse *xsk_reuseq_prepare(u32 nentries);
> +struct xdp_umem_fq_reuse *xsk_reuseq_swap(struct xdp_umem *umem,
> + struct xdp_umem_fq_reuse *newq);
> +void xsk_reuseq_free(struct xdp_umem_fq_reuse *rq);
> +
> +/* Reuse-queue aware version of FILL queue helpers */
> +static inline u64 *xsk_umem_peek_addr_rq(struct xdp_umem *umem, u64 *addr)
> +{
> + struct xdp_umem_fq_reuse *rq = umem->fq_reuse;
> +
> + if (!rq->length) {
> + return xsk_umem_peek_addr(umem, addr);
> + } else {
> + *addr = rq->handles[rq->length - 1];
> + return addr;
> + }
> +}
> +
> +static inline void xsk_umem_discard_addr_rq(struct xdp_umem *umem)
> +{
> + struct xdp_umem_fq_reuse *rq = umem->fq_reuse;
> +
> + if (!rq->length)
> + xsk_umem_discard_addr(umem);
> + else
> + rq->length--;
> +}
> +
> +static inline void xsk_umem_fq_reuse(struct xdp_umem *umem, u64 addr)
> +{
> + struct xdp_umem_fq_reuse *rq = umem->fq_reuse;
> +
> + rq->handles[rq->length++] = addr;
> +}
> +
> #endif /* _LINUX_XDP_SOCK_H */
> diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
> index e762310c9bee..40303e24c954 100644
> --- a/net/xdp/xdp_umem.c
> +++ b/net/xdp/xdp_umem.c
> @@ -170,6 +170,8 @@ static void xdp_umem_release(struct xdp_umem *umem)
> umem->cq = NULL;
> }
>
> + xsk_reuseq_destroy(umem);
> +
> xdp_umem_unpin_pages(umem);
>
> task = get_pid_task(umem->pid, PIDTYPE_PID);
> diff --git a/net/xdp/xsk_queue.c b/net/xdp/xsk_queue.c
> index 6c32e92e98fc..f9ee40a13a9a 100644
> --- a/net/xdp/xsk_queue.c
> +++ b/net/xdp/xsk_queue.c
> @@ -3,7 +3,9 @@
> * Copyright(c) 2018 Intel Corporation.
> */
>
> +#include <linux/log2.h>
> #include <linux/slab.h>
> +#include <linux/overflow.h>
>
> #include "xsk_queue.h"
>
> @@ -61,3 +63,57 @@ void xskq_destroy(struct xsk_queue *q)
> page_frag_free(q->ring);
> kfree(q);
> }
> +
> +struct xdp_umem_fq_reuse *xsk_reuseq_prepare(u32 nentries)
> +{
> + struct xdp_umem_fq_reuse *newq;
> +
> + /* Check for overflow */
> + if (nentries > (u32)roundup_pow_of_two(nentries))
> + return NULL;
> + nentries = roundup_pow_of_two(nentries);
> +
> + newq = kvmalloc(struct_size(newq, handles, nentries), GFP_KERNEL);
> + if (!newq)
> + return NULL;
> + memset(newq, 0, offsetof(typeof(*newq), handles));
> +
> + newq->nentries = nentries;
> + return newq;
> +}
> +EXPORT_SYMBOL_GPL(xsk_reuseq_prepare);
> +
> +struct xdp_umem_fq_reuse *xsk_reuseq_swap(struct xdp_umem *umem,
> + struct xdp_umem_fq_reuse *newq)
> +{
> + struct xdp_umem_fq_reuse *oldq = umem->fq_reuse;
> +
> + if (!oldq) {
> + umem->fq_reuse = newq;
> + return NULL;
> + }
> +
> + if (newq->nentries < oldq->length)
> + return newq;
> +
> +
> + memcpy(newq->handles, oldq->handles,
> + array_size(oldq->length, sizeof(u64)));
> + newq->length = oldq->length;
> +
> + umem->fq_reuse = newq;
> + return oldq;
> +}
> +EXPORT_SYMBOL_GPL(xsk_reuseq_swap);
> +
> +void xsk_reuseq_free(struct xdp_umem_fq_reuse *rq)
> +{
> + kvfree(rq);
> +}
> +EXPORT_SYMBOL_GPL(xsk_reuseq_free);
> +
> +void xsk_reuseq_destroy(struct xdp_umem *umem)
> +{
> + xsk_reuseq_free(umem->fq_reuse);
> + umem->fq_reuse = NULL;
> +}
> diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
> index 8a64b150be54..7a480e3eb35d 100644
> --- a/net/xdp/xsk_queue.h
> +++ b/net/xdp/xsk_queue.h
> @@ -257,4 +257,7 @@ void xskq_set_umem(struct xsk_queue *q, struct xdp_umem_props *umem_props);
> struct xsk_queue *xskq_create(u32 nentries, bool umem_queue);
> void xskq_destroy(struct xsk_queue *q_ops);
>
> +/* Executed by the core when the entire UMEM gets freed */
> +void xsk_reuseq_destroy(struct xdp_umem *umem);
> +
> #endif /* _LINUX_XSK_QUEUE_H */
>
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