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net/tcp: Only call grub_get_time_ms() when there are sockets to potentially retransmit for

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If the machine has network cards found, but there are no tcp open sockets
(because the user doesn't use the network to boot), then grub_net_tcp_retransmit()
should be a noop. Thus GRUB doesn't need to call grub_get_time_ms(), which
does a call into firmware on powerpc-ieee1275, and probably other targets.
So only call grub_get_time_ms() if there are tcp sockets.

Aside from improving performance, its also useful to stay out of the firmware
as much as possible when debugging via QEMU because its a pain to get back
in to GRUB execution. grub_net_tcp_retransmit() can get called very frequently
via grub_net_poll_cards_idle() when GRUB is waiting for a keypress
(grub_getkey_noblock() calls grub_net_poll_cards_idle()). This can be annoying
when debugging an issue in GRUB on PowerPC in QEMU with GDB when GRUB is waiting
for a keypress because interrupting via GDB nearly always lands in the OpenBIOS
firmware's milliseconds call.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Glenn Washburn 2022-03-18 01:51:33 -05:00 committed by Daniel Kiper
parent 848724273e
commit c2e5dc6916
1 changed files with 7 additions and 2 deletions
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9
grub-core/net/tcp.c
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@ -362,8 +362,13 @@ void
grub_net_tcp_retransmit (void)
{
grub_net_tcp_socket_t sock;
grub_uint64_t ctime = grub_get_time_ms ();
grub_uint64_t limit_time = ctime - TCP_RETRANSMISSION_TIMEOUT;
grub_uint64_t ctime = 0, limit_time = 0;
if (tcp_sockets != NULL)
{
ctime = grub_get_time_ms ();
limit_time = ctime - TCP_RETRANSMISSION_TIMEOUT;
}
FOR_TCP_SOCKETS (sock)
{