src/patches/60056_xen-netback-nr-irqs.patch1

   1 From: jbeulich@novell.com
   2 Subject: netback: reduce overhead of IRQ recording
   3 Patch-mainline: obsolete
   4
   5 Since both NR_PIRQS and NR_DYNIRQS are no longer hardcoded, the
   6 (memory) overhead of tracking which ones to send notifications to can
   7 be pretty unbounded. Also, store the dynirq rather than the raw irq
   8 to push up the limit where the type of notify_list needs to become
   9 'int' rather than 'u16'.
  10
  11 Index: head-2008-12-01/drivers/xen/netback/interface.c
  12 ===================================================================
  13 --- head-2008-12-01.orig/drivers/xen/netback/interface.c        2007-06-12 13:13:45.000000000 +0200
  14 +++ head-2008-12-01/drivers/xen/netback/interface.c     2008-12-01 12:10:26.000000000 +0100
  15 @@ -273,6 +273,7 @@ int netif_map(netif_t *netif, unsigned l
  16                 netif->dev->name, netif);
  17         if (err < 0)
  18                 goto err_hypervisor;
  19 +       BUG_ON(err < DYNIRQ_BASE || err >= DYNIRQ_BASE + NR_DYNIRQS);
  20         netif->irq = err;
  21         disable_irq(netif->irq);
  22
  23 Index: head-2008-12-01/drivers/xen/netback/netback.c
  24 ===================================================================
  25 --- head-2008-12-01.orig/drivers/xen/netback/netback.c  2008-12-01 12:10:23.000000000 +0100
  26 +++ head-2008-12-01/drivers/xen/netback/netback.c       2008-12-01 12:10:26.000000000 +0100
  27 @@ -564,8 +564,12 @@ static void net_rx_action(unsigned long
  28         static mmu_update_t rx_mmu[NET_RX_RING_SIZE];
  29         static gnttab_transfer_t grant_trans_op[NET_RX_RING_SIZE];
  30         static gnttab_copy_t grant_copy_op[NET_RX_RING_SIZE];
  31 -       static unsigned char rx_notify[NR_IRQS];
  32 +       static DECLARE_BITMAP(rx_notify, NR_DYNIRQS);
  33 +#if NR_DYNIRQS <= 0x10000
  34         static u16 notify_list[NET_RX_RING_SIZE];
  35 +#else
  36 +       static int notify_list[NET_RX_RING_SIZE];
  37 +#endif
  38         static struct netbk_rx_meta meta[NET_RX_RING_SIZE];
  39
  40         struct netrx_pending_operations npo = {
  41 @@ -714,11 +718,9 @@ static void net_rx_action(unsigned long
  42                                          nr_frags);
  43
  44                 RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&netif->rx, ret);
  45 -               irq = netif->irq;
  46 -               if (ret && !rx_notify[irq]) {
  47 -                       rx_notify[irq] = 1;
  48 +               irq = netif->irq - DYNIRQ_BASE;
  49 +               if (ret && !__test_and_set_bit(irq, rx_notify))
  50                         notify_list[notify_nr++] = irq;
  51 -               }
  52
  53                 if (netif_queue_stopped(netif->dev) &&
  54                     netif_schedulable(netif) &&
  55 @@ -732,8 +734,8 @@ static void net_rx_action(unsigned long
  56
  57         while (notify_nr != 0) {
  58                 irq = notify_list[--notify_nr];
  59 -               rx_notify[irq] = 0;
  60 -               notify_remote_via_irq(irq);
  61 +               __clear_bit(irq, rx_notify);
  62 +               notify_remote_via_irq(irq + DYNIRQ_BASE);
  63         }
  64
  65         /* More work to do? */