From: David Gibson <david@gibson.dropbear.id.au>
To: Laurent Vivier <lvivier@redhat.com>
Cc: passt-dev@passt.top
Subject: Re: [PATCH v8 30/30] packet: Add support for multi-vector packets
Date: Thu, 7 Aug 2025 16:17:33 +1000 [thread overview]
Message-ID: <aJRE_cdkV7sNt3OZ@zatzit> (raw)
In-Reply-To: <20250805154628.301343-31-lvivier@redhat.com>
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On Tue, Aug 05, 2025 at 05:46:28PM +0200, Laurent Vivier wrote:
> The packet pool was previously limited to handling packets contained
> within a single buffer.
>
> This patch extends the packet pool to support iovec array,
> allowing a single logical packet to be composed of multiple iovec.
>
> To accommodate this, the storage format within the pool is modified.
> For a multi-vector packet, a header entry is now stored first with
> iov_base = NULL and iov_len holding the number of subsequent
> vectors. The actual data vectors are then stored in the following
> pool slots.
>
> The packet_add_do() and packet_get_do() functions are updated to
> manage this new format for storing and retrieving packets. The
> pool_full() check is also adjusted to ensure there is enough
> space for all vectors of a new packet before adding it.
>
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
> packet.c | 50 +++++++++++++++++++++++++++++++++-----------------
> packet.h | 2 +-
> tap.c | 4 ++--
> 3 files changed, 36 insertions(+), 20 deletions(-)
>
> diff --git a/packet.c b/packet.c
> index 4b93688509a4..d697232d951a 100644
> --- a/packet.c
> +++ b/packet.c
> @@ -90,12 +90,13 @@ static int packet_check_range(const struct pool *p, const char *ptr, size_t len,
> /**
> * pool_full() - Is a packet pool full?
> * @p: Pointer to packet pool
> + * @data: check data can fit in the pool
> *
> - * Return: true if the pool is full, false if more packets can be added
> + * Return: true if the pool is full, false if data can be added
> */
> -bool pool_full(const struct pool *p)
> +bool pool_full(const struct pool *p, const struct iov_tail *data)
Given the slightly changed semantics, I wonder if 'pool_can_fit()'
might be a better name now.
> {
> - return p->count >= p->size;
> + return p->count + data->cnt + (data->cnt > 1) >= p->size;
This test is only correct if data is already pruned. As I've said
elsewhere, it might be worth changing to the assumption that iov_tails
are pruned everywhere outside the iov_tail internal handling.
Oh.. also I think the new check is off by one (in the relatively safe
direction). It will say there's no room when there is just exactly
enough room.
> }
>
> /**
> @@ -108,11 +109,9 @@ bool pool_full(const struct pool *p)
> void packet_add_do(struct pool *p, struct iov_tail *data,
> const char *func, int line)
> {
> - size_t idx = p->count;
> - const char *start;
> - size_t len;
> + size_t idx = p->count, i, offset;
>
> - if (pool_full(p)) {
> + if (pool_full(p, data)) {
> debug("add packet index %zu to pool with size %zu, %s:%i",
> idx, p->size, func, line);
> return;
> @@ -121,18 +120,30 @@ void packet_add_do(struct pool *p, struct iov_tail *data,
> if (!iov_tail_prune(data))
> return;
>
> - ASSERT(data->cnt == 1); /* we don't support iovec */
> + if (data->cnt > 1) {
> + p->pkt[idx].iov_base = NULL;
> + p->pkt[idx].iov_len = data->cnt;
> + idx++;
> + }
>
> - len = data->iov[0].iov_len - data->off;
> - start = (char *)data->iov[0].iov_base + data->off;
> + offset = data->off;
> + for (i = 0; i < data->cnt; i++) {
> + const char *start;
> + size_t len;
>
> - if (packet_check_range(p, start, len, func, line))
> - return;
> + len = data->iov[i].iov_len - offset;
> + start = (char *)data->iov[i].iov_base + offset;
> + offset = 0;
>
> - p->pkt[idx].iov_base = (void *)start;
> - p->pkt[idx].iov_len = len;
> + if (packet_check_range(p, start, len, func, line))
> + return;
>
> - p->count++;
> + p->pkt[idx].iov_base = (void *)start;
> + p->pkt[idx].iov_len = len;
> + idx++;
Hm. Isn't the above equivalent to iov_tail_clone()? Is calling
packet_check_range() on each chunk the only reason for open-coding it
here?
> + }
> +
> + p->count = idx;
> }
>
> /**
> @@ -162,9 +173,14 @@ bool packet_get_do(const struct pool *p, size_t idx,
> return false;
> }
>
> - data->cnt = 1;
> + if (p->pkt[idx].iov_base) {
> + data->cnt = 1;
> + data->iov = &p->pkt[idx];
> + } else {
> + data->cnt = p->pkt[idx].iov_len;
> + data->iov = &p->pkt[idx + 1];
> + }
> data->off = 0;
> - data->iov = &p->pkt[idx];
>
> for (i = 0; i < data->cnt; i++) {
> ASSERT_WITH_MSG(!packet_check_range(p, data->iov[i].iov_base,
> diff --git a/packet.h b/packet.h
> index e51cbd19fdc4..67dc7deb17db 100644
> --- a/packet.h
> +++ b/packet.h
> @@ -37,7 +37,7 @@ void packet_add_do(struct pool *p, struct iov_tail *data,
> const char *func, int line);
> bool packet_get_do(const struct pool *p, const size_t idx,
> struct iov_tail *data, const char *func, int line);
> -bool pool_full(const struct pool *p);
> +bool pool_full(const struct pool *p, const struct iov_tail *data);
> void pool_flush(struct pool *p);
>
> #define packet_add(p, data) \
> diff --git a/tap.c b/tap.c
> index 9fd00915bb01..95688b22fcb7 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -1103,14 +1103,14 @@ void tap_add_packet(struct ctx *c, struct iov_tail *data,
> switch (ntohs(eh->h_proto)) {
> case ETH_P_ARP:
> case ETH_P_IP:
> - if (pool_full(pool_tap4)) {
> + if (pool_full(pool_tap4, data)) {
> tap4_handler(c, pool_tap4, now);
> pool_flush(pool_tap4);
> }
> packet_add(pool_tap4, data);
> break;
> case ETH_P_IPV6:
> - if (pool_full(pool_tap6)) {
> + if (pool_full(pool_tap6, data)) {
> tap6_handler(c, pool_tap6, now);
> pool_flush(pool_tap6);
> }
--
David Gibson (he or they) | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you, not the other way
| around.
http://www.ozlabs.org/~dgibson
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prev parent reply other threads:[~2025-08-07 6:18 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-05 15:45 [PATCH v8 00/30] Introduce discontiguous frames management Laurent Vivier
2025-08-05 15:45 ` [PATCH v8 01/30] arp: Don't mix incoming and outgoing buffers Laurent Vivier
2025-08-05 15:46 ` [PATCH v8 02/30] iov: Introduce iov_tail_clone() and iov_tail_drop() Laurent Vivier
2025-08-06 1:32 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 03/30] iov: Update IOV_REMOVE_HEADER() and IOV_PEEK_HEADER() Laurent Vivier
2025-08-06 1:45 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 04/30] tap: Use iov_tail with tap_add_packet() Laurent Vivier
2025-08-06 1:56 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 05/30] packet: Use iov_tail with packet_add() Laurent Vivier
2025-08-05 15:46 ` [PATCH v8 06/30] packet: Add packet_data() Laurent Vivier
2025-08-06 2:14 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 07/30] arp: Convert to iov_tail Laurent Vivier
2025-08-06 2:17 ` David Gibson
2025-08-07 12:58 ` Laurent Vivier
2025-08-07 13:11 ` Stefano Brivio
2025-08-13 2:21 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 08/30] ndp: " Laurent Vivier
2025-08-05 15:46 ` [PATCH v8 09/30] icmp: " Laurent Vivier
2025-08-06 2:20 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 10/30] udp: " Laurent Vivier
2025-08-06 2:23 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 11/30] tcp: Convert tcp_tap_handler() to use iov_tail Laurent Vivier
2025-08-06 2:35 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 12/30] tcp: Convert tcp_data_from_tap() " Laurent Vivier
2025-08-06 2:37 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 13/30] dhcpv6: move offset initialization out of dhcpv6_opt() Laurent Vivier
2025-08-05 15:46 ` [PATCH v8 14/30] dhcpv6: Extract sending of NotOnLink status Laurent Vivier
2025-08-05 15:46 ` [PATCH v8 15/30] dhcpv6: Convert to iov_tail Laurent Vivier
2025-08-05 15:46 ` [PATCH v8 16/30] dhcpv6: Use iov_tail in dhcpv6_opt() Laurent Vivier
2025-08-06 4:14 ` David Gibson
2025-08-08 13:59 ` Laurent Vivier
2025-08-13 2:29 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 17/30] dhcp: Convert to iov_tail Laurent Vivier
2025-08-06 4:38 ` David Gibson
2025-08-08 9:33 ` Laurent Vivier
2025-08-13 2:27 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 18/30] ip: Use iov_tail in ipv6_l4hdr() Laurent Vivier
2025-08-06 5:12 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 19/30] tap: Convert tap4_handler() to iov_tail Laurent Vivier
2025-08-06 5:17 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 20/30] tap: Convert tap6_handler() " Laurent Vivier
2025-08-06 6:21 ` David Gibson
2025-08-08 13:57 ` Laurent Vivier
2025-08-13 3:22 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 21/30] packet: rename packet_data() to packet_get() Laurent Vivier
2025-08-06 6:22 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 22/30] arp: use iov_tail rather than pool Laurent Vivier
2025-08-06 6:24 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 23/30] dhcp: " Laurent Vivier
2025-08-06 6:26 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 24/30] dhcpv6: " Laurent Vivier
2025-08-06 6:27 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 25/30] icmp: " Laurent Vivier
2025-08-06 6:29 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 26/30] ndp: " Laurent Vivier
2025-08-06 6:31 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 27/30] packet: remove PACKET_POOL() and PACKET_POOL_P() Laurent Vivier
2025-08-06 6:32 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 28/30] packet: remove unused parameter from PACKET_POOL_DECL() Laurent Vivier
2025-08-06 6:33 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 29/30] packet: Refactor vhost-user memory region handling Laurent Vivier
2025-08-07 6:10 ` David Gibson
2025-08-07 9:05 ` Laurent Vivier
2025-08-07 11:44 ` David Gibson
2025-08-05 15:46 ` [PATCH v8 30/30] packet: Add support for multi-vector packets Laurent Vivier
2025-08-07 6:17 ` David Gibson [this message]
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