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Refactor TCP ISN increment logic. Instead of firing callout at 100Hz to

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keep constant ISN growth rate, do the same directly inside tcp_new_isn(),
taking into account how much time (ticks) passed since the last call.

On my test systems this decreases idle interrupt rate from 140Hz to 70Hz.
This commit is contained in:
Alexander Motin 2011-05-09 07:37:47 +00:00
parent 07eb7033a6
commit bc7d18ae72
1 changed files with 11 additions and 34 deletions
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45
sys/netinet/tcp_subr.c
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@ -224,7 +224,6 @@ VNET_DEFINE(uma_zone_t, sack_hole_zone);
VNET_DEFINE(struct hhook_head *, tcp_hhh[HHOOK_TCP_LAST+1]);
static struct inpcb *tcp_notify(struct inpcb *, int);
static void tcp_isn_tick(void *);
static char * tcp_log_addr(struct in_conninfo *inc, struct tcphdr *th,
void *ip4hdr, const void *ip6hdr);
@ -255,7 +254,6 @@ static VNET_DEFINE(uma_zone_t, tcpcb_zone);
#define V_tcpcb_zone VNET(tcpcb_zone)
MALLOC_DEFINE(M_TCPLOG, "tcplog", "TCP address and flags print buffers");
struct callout isn_callout;
static struct mtx isn_mtx;
#define ISN_LOCK_INIT() mtx_init(&isn_mtx, "isn_mtx", NULL, MTX_DEF)
@ -358,8 +356,6 @@ tcp_init(void)
#undef TCP_MINPROTOHDR
ISN_LOCK_INIT();
callout_init(&isn_callout, CALLOUT_MPSAFE);
callout_reset(&isn_callout, hz/100, tcp_isn_tick, NULL);
EVENTHANDLER_REGISTER(shutdown_pre_sync, tcp_fini, NULL,
SHUTDOWN_PRI_DEFAULT);
EVENTHANDLER_REGISTER(maxsockets_change, tcp_zone_change, NULL,
@ -385,7 +381,6 @@ void
tcp_fini(void *xtp)
{
callout_stop(&isn_callout);
}
/*
@ -1571,11 +1566,13 @@ tcp6_ctlinput(int cmd, struct sockaddr *sa, void *d)
#define ISN_RANDOM_INCREMENT (4096 - 1)
static VNET_DEFINE(u_char, isn_secret[32]);
static VNET_DEFINE(int, isn_last);
static VNET_DEFINE(int, isn_last_reseed);
static VNET_DEFINE(u_int32_t, isn_offset);
static VNET_DEFINE(u_int32_t, isn_offset_old);
#define V_isn_secret VNET(isn_secret)
#define V_isn_last VNET(isn_last)
#define V_isn_last_reseed VNET(isn_last_reseed)
#define V_isn_offset VNET(isn_offset)
#define V_isn_offset_old VNET(isn_offset_old)
@ -1586,6 +1583,7 @@ tcp_new_isn(struct tcpcb *tp)
MD5_CTX isn_ctx;
u_int32_t md5_buffer[4];
tcp_seq new_isn;
u_int32_t projected_offset;
INP_WLOCK_ASSERT(tp->t_inpcb);
@ -1621,40 +1619,19 @@ tcp_new_isn(struct tcpcb *tp)
new_isn = (tcp_seq) md5_buffer[0];
V_isn_offset += ISN_STATIC_INCREMENT +
(arc4random() & ISN_RANDOM_INCREMENT);
if (ticks != V_isn_last) {
projected_offset = V_isn_offset_old +
ISN_BYTES_PER_SECOND / hz * (ticks - V_isn_last);
if (SEQ_GT(projected_offset, V_isn_offset))
V_isn_offset = projected_offset;
V_isn_offset_old = V_isn_offset;
V_isn_last = ticks;
}
new_isn += V_isn_offset;
ISN_UNLOCK();
return (new_isn);
}
/*
* Increment the offset to the next ISN_BYTES_PER_SECOND / 100 boundary
* to keep time flowing at a relatively constant rate. If the random
* increments have already pushed us past the projected offset, do nothing.
*/
static void
tcp_isn_tick(void *xtp)
{
VNET_ITERATOR_DECL(vnet_iter);
u_int32_t projected_offset;
VNET_LIST_RLOCK_NOSLEEP();
ISN_LOCK();
VNET_FOREACH(vnet_iter) {
CURVNET_SET(vnet_iter); /* XXX appease INVARIANTS */
projected_offset =
V_isn_offset_old + ISN_BYTES_PER_SECOND / 100;
if (SEQ_GT(projected_offset, V_isn_offset))
V_isn_offset = projected_offset;
V_isn_offset_old = V_isn_offset;
CURVNET_RESTORE();
}
ISN_UNLOCK();
VNET_LIST_RUNLOCK_NOSLEEP();
callout_reset(&isn_callout, hz/100, tcp_isn_tick, NULL);
}
/*
* When a specific ICMP unreachable message is received and the
* connection state is SYN-SENT, drop the connection. This behavior