Re: [PATCH 4/7] flow: Delegate epoll file descriptor management to threading subsystem

On Fri, Jul 31, 2026 at 06:46:25PM +0200, Laurent Vivier wrote:

Remove the flow-local epoll_id_to_fd mapping array and instead rely on the threading subsystem to provide the epoll file descriptor for a given thread number.

Update all protocol handlers (ICMP, TCP, TCP splice, UDP).

Signed-off-by: Laurent Vivier --- flow.c | 17 +++++++++-------- flow.h | 4 +--- passt.c | 2 +- tcp.c | 3 ++- 4 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/flow.c b/flow.c index 3012a07ed680..7821b3f91285 100644 --- a/flow.c +++ b/flow.c @@ -24,6 +24,7 @@ #include "repair.h" #include "epoll_ctl.h" #include "serialise.h" +#include "threading.h"

const char *flow_state_str[] = { [FLOW_STATE_FREE] = "FREE", @@ -221,7 +222,6 @@ static_assert(ARRAY_SIZE(flow_epoll) == FLOW_NUM_TYPES, unsigned flow_first_free; union flow flowtab[FLOW_MAX]; static _Thread_local const union flow *flow_new_entry; /* = NULL */ -int qpair_to_fd[FLOW_QPAIR_SIZE];

/* Hash table to index it */ #define FLOW_HASH_LOAD 70 /* % */ @@ -457,7 +457,12 @@ static void flow_set_state(struct flow_common *f, enum flow_state state) */ int flow_epollfd(const struct flow_common *f) { - return qpair_to_fd[f->qpair]; + /* mapping 1:1 between qpair and threadid + * return threading_epollfd(f->qpair); + * but for the moment we have only one thread + */ + (void)f; + return threading_epollfd(THREADING_ID_DEFAULT);

This seems like it's going backwards, always using thread 0's epollfd, rather than choosing the right thread based on the qpair.

}

/** @@ -525,7 +530,7 @@ bool flow_migrate_epollfd(struct flow_common *f, unsigned int qpair, flow_trace((union flow *)f, "migrating from qpair %d to %d", qpair, target);

- epoll_del(qpair_to_fd[qpair], ref.fd); + epoll_del(threading_epollfd(qpair), ref.fd); flow_setqp(f, target); flow_epoll_set(f, EPOLL_CTL_ADD, events, ref.fd, ref.flowside.sidei); ret = true; @@ -1444,9 +1449,8 @@ int flow_migrate_target(struct ctx *c, const struct migrate_stage *stage,

/** * flow_init() - Initialise flow related data structures - * @c: Execution context */ -void flow_init(const struct ctx *c) +void flow_init(void) { unsigned b;

@@ -1456,7 +1460,4 @@ void flow_init(const struct ctx *c)

for (b = 0; b < FLOW_HASH_SIZE; b++) flow_hashtab[b] = FLOW_SIDX_NONE; - - for (b = 0; b < FLOW_QPAIR_SIZE; b++) - qpair_to_fd[b] = c->epollfd; } diff --git a/flow.h b/flow.h index c31a51a9cc96..e2693efd0f70 100644 --- a/flow.h +++ b/flow.h @@ -157,8 +157,6 @@ struct flowside { in_port_t eport; };

-extern int qpair_to_fd[]; - /** * flowside_eq() - Check if two flowsides are equal * @left, @right: Flowsides to compare @@ -266,7 +264,7 @@ flow_sidx_t flow_lookup_sa(const struct ctx *c, uint8_t proto, uint8_t pif,

union flow;

-void flow_init(const struct ctx *c); +void flow_init(void); int flow_epollfd(const struct flow_common *f); int flow_epoll_set(const struct flow_common *f, int command, uint32_t events, int fd, unsigned int sidei); diff --git a/passt.c b/passt.c index 2cedb7ba0756..57290a5a7c6e 100644 --- a/passt.c +++ b/passt.c @@ -399,7 +399,7 @@ int main(int argc, char **argv) if (clock_gettime(CLOCK_MONOTONIC, &now)) die_perror("Failed to get CLOCK_MONOTONIC time");

- flow_init(c); + flow_init(); fwd_scan_ports_init(c);

if ((!c->no_udp && udp_init(c)) || (!c->no_tcp && tcp_init(c))) diff --git a/tcp.c b/tcp.c index 2767a8494107..e8da65410bcf 100644 --- a/tcp.c +++ b/tcp.c @@ -317,6 +317,7 @@ #include "tcp_buf.h" #include "tcp_vu.h" #include "epoll_ctl.h" +#include "threading.h"

/* * The size of TCP header (including options) is given by doff (Data Offset) @@ -2721,7 +2722,7 @@ void tcp_timer_handler(const struct ctx *c, union epoll_ref ref, assert(conn->f.type == FLOW_TCP);

if (conn->f.qpair != qpair) { - int old_epollfd = qpair_to_fd[qpair]; + int old_epollfd = threading_epollfd(qpair);

epoll_del(old_epollfd, conn->timer); if (tcp_timer_epoll_add(conn, conn->timer, now) < 0) { -- 2.54.0

-- 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