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Recycle old buffers into new rx requests when their number reaches half of 

those not tied up in active mbufs, rather than half of the total number.

(Or, to more literally translate the C, when there are at least as
many buffers waiting to be reused as outstanding rx requests.)

This prevents us from dropping off the network for a while when more
than 128 of the 256 buffers are in use by mbufs, which might not be
freed for an arbitrarily long time; the remaining buffers would stack up
on the free list but not be reclaimed until enough mbufs were eventually
freed, leaving the interface unable to receive packets until then.
This commit is contained in:
jld 2006-11-03 03:03:32 +00:00
parent de3426b487
commit 2d61afc3e7
1 changed files with 5 additions and 3 deletions
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8
sys/arch/xen/xen/if_xennet_xenbus.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: if_xennet_xenbus.c,v 1.13 2006/07/12 15:03:08 yamt Exp $ */
/* $NetBSD: if_xennet_xenbus.c,v 1.14 2006/11/03 03:03:32 jld Exp $ */
/*
* Copyright (c) 2006 Manuel Bouyer.
@ -61,7 +61,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: if_xennet_xenbus.c,v 1.13 2006/07/12 15:03:08 yamt Exp $");
__KERNEL_RCSID(0, "$NetBSD: if_xennet_xenbus.c,v 1.14 2006/11/03 03:03:32 jld Exp $");
#include "opt_xen.h"
#include "opt_nfs_boot.h"
@ -176,6 +176,8 @@ struct xennet_xenbus_softc {
rndsource_element_t sc_rnd_source;
#endif
};
#define SC_NLIVEREQ(sc) ((sc)->sc_rx_ring.req_prod_pvt - \
(sc)->sc_rx_ring.sring->rsp_prod)
/* too big to be on stack */
static multicall_entry_t rx_mcl[NET_RX_RING_SIZE+1];
@ -658,7 +660,7 @@ xennet_rx_mbuf_free(struct mbuf *m, caddr_t buf, size_t size, void *arg)
sc->sc_free_rxreql++;
req->rxreq_gntref = GRANT_INVALID_REF;
if (sc->sc_free_rxreql >= NET_RX_RING_SIZE / 2 &&
if (sc->sc_free_rxreql >= SC_NLIVEREQ(sc) &&
__predict_true(sc->sc_backend_status == BEST_CONNECTED)) {
xennet_alloc_rx_buffer(sc);
}