Date: Sat, 13 Oct 2012 21:49:21 +0400 From: "Alexander V. Chernikov" <melifaro@FreeBSD.org> To: net@freebsd.org Cc: Jack Vogel <jfvogel@gmail.com> Subject: ixgbe & if_igb RX ring locking Message-ID: <5079A9A1.4070403@FreeBSD.org>
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Hello list!
Packets receiving code for both ixgbe and if_igb looks like the following:
ixgbe_msix_que
-- ixgbe_rxeof()
{
IXGBE_RX_LOCK(rxr);
while
{
get_packet;
-- ixgbe_rx_input()
{
++ IXGBE_RX_UNLOCK(rxr);
if_input(packet);
++ IXGBE_RX_LOCK(rxr);
}
}
IXGBE_RX_UNLOCK(rxr);
}
Lines marked with ++ appeared in r209068(igb) and r217593(ixgbe).
These lines probably do LORs masking (if any) well.
However, such change introduce quite significant performance drop:
On my routing setup (nearly the same from previous -Intel 10G thread in
-net) adding lock/unlock causes 2.8MPPS decrease to 2.3MPPS which is
nearly 20%.
So my questions are:
Can any real LORs happen in some complex setup? (I can't imagine any).
If so: maybe we can somehow avoid/workaround such cases? (and consider
removing those locks).
--
WBR, Alexander
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