[PATCH 9/10] [IOAT] Add sysctl to tuning IOAT offloaded IO threshold

[PATCH 9/10] [IOAT] Add sysctl to tuning IOAT offloaded IO threshold

[Andrew Grover]

Any socket recv of less than this ammount will not be offloaded

Signed-off-by: Chris Leech <christopher.leech@intel.com>

---

 include/linux/sysctl.h     |    1 +
 include/net/tcp.h          |    1 +
 net/core/user_dma.c        |    4 ++++
 net/ipv4/sysctl_net_ipv4.c |   10 ++++++++++

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 76eaeff..cd9e7c0 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -403,6 +403,7 @@ enum
  	NET_TCP_MTU_PROBING=113,
 	NET_TCP_BASE_MSS=114,
 	NET_IPV4_TCP_WORKAROUND_SIGNED_WINDOWS=115,
+	NET_TCP_DMA_COPYBREAK=116,
 };
 
 enum {
diff --git a/include/net/tcp.h b/include/net/tcp.h
index ca5bdaf..2e6fdef 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -219,6 +219,7 @@ extern int sysctl_tcp_adv_win_scale;
 extern int sysctl_tcp_tw_reuse;
 extern int sysctl_tcp_frto;
 extern int sysctl_tcp_low_latency;
+extern int sysctl_tcp_dma_copybreak;
 extern int sysctl_tcp_nometrics_save;
 extern int sysctl_tcp_moderate_rcvbuf;
 extern int sysctl_tcp_tso_win_divisor;
diff --git a/net/core/user_dma.c b/net/core/user_dma.c
index ec177ef..642a3f3 100644
--- a/net/core/user_dma.c
+++ b/net/core/user_dma.c
@@ -33,6 +33,10 @@
 
 #ifdef CONFIG_NET_DMA
 
+#define NET_DMA_DEFAULT_COPYBREAK 1024
+
+int sysctl_tcp_dma_copybreak = NET_DMA_DEFAULT_COPYBREAK;
+
 /**
  *	dma_skb_copy_datagram_iovec - Copy a datagram to an iovec.
  *	@skb - buffer to copy
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 6b6c3ad..6a6aa53 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -688,6 +688,16 @@ ctl_table ipv4_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec
 	},
+#ifdef CONFIG_NET_DMA
+	{
+		.ctl_name	= NET_TCP_DMA_COPYBREAK,
+		.procname	= "tcp_dma_copybreak",
+		.data		= &sysctl_tcp_dma_copybreak,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec
+	},
+#endif
 	{ .ctl_name = 0 }
 };
 
-- 
1.2.6

Re: [PATCH 9/10] [IOAT] Add sysctl to tuning IOAT offloaded IO threshold

[Olof Johansson]

Hi,

On Thu, Apr 20, 2006 at 01:50:40PM -0700, Andrew Grover wrote:
> 
> Any socket recv of less than this ammount will not be offloaded
[...]
> --- a/net/core/user_dma.c
> +++ b/net/core/user_dma.c
> @@ -33,6 +33,10 @@
>  
>  #ifdef CONFIG_NET_DMA
>  
> +#define NET_DMA_DEFAULT_COPYBREAK 1024
> +
> +int sysctl_tcp_dma_copybreak = NET_DMA_DEFAULT_COPYBREAK;
> +

The breakpoint is highly likely to be at different points on various
architectures and platforms depending on what they look like, where in
the system the DMA engine is, how efficient regular memcpy is, etc.

I would like to see it as a config option instead, so it will at least
be possible to tune per-arch (via default config, etc).


-Olof