[PATCH 13/29] netvm: link network to vm layer

[Peter Zijlstra]

Hook up networking to the memory reserve.

There are two kinds of reserves: skb and aux. 
 - skb reserves are used for incomming packets,
 - aux reserves are used for processing these packets.

The consumers for these reserves are sockets marked with:
  SOCK_VMIO

Such sockets are to be used to service the VM (iow. to swap over). They
must be handled kernel side, exposing such a socket to user-space is a BUG.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 include/net/sock.h |   31 ++++++++++++
 net/Kconfig        |    3 +
 net/core/sock.c    |  134 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 168 insertions(+)

Index: linux-2.6-git/include/net/sock.h
===================================================================
--- linux-2.6-git.orig/include/net/sock.h	2007-02-20 15:06:17.000000000 +0100
+++ linux-2.6-git/include/net/sock.h	2007-02-20 15:07:45.000000000 +0100
@@ -392,6 +392,7 @@ enum sock_flags {
 	SOCK_RCVTSTAMP, /* %SO_TIMESTAMP setting */
 	SOCK_LOCALROUTE, /* route locally only, %SO_DONTROUTE setting */
 	SOCK_QUEUE_SHRUNK, /* write queue has been shrunk recently */
+	SOCK_VMIO, /* the VM depends on us - make sure we're serviced */
 };
 
 static inline void sock_copy_flags(struct sock *nsk, struct sock *osk)
@@ -414,6 +415,36 @@ static inline int sock_flag(struct sock 
 	return test_bit(flag, &sk->sk_flags);
 }
 
+static inline int sk_has_vmio(struct sock *sk)
+{
+	return sock_flag(sk, SOCK_VMIO);
+}
+
+#define MAX_PAGES_PER_SKB 3
+#define MAX_FRAGMENTS ((65536 + 1500 - 1) / 1500)
+/*
+ * Guestimate the per request queue TX upper bound.
+ */
+#define TX_RESERVE_PAGES \
+	(4 * MAX_FRAGMENTS * MAX_PAGES_PER_SKB)
+
+extern atomic_t vmio_socks;
+
+static inline int sk_vmio_socks(void)
+{
+	return atomic_read(&vmio_socks);
+}
+
+extern int rx_emergency_get(int bytes);
+extern int rx_emergency_get_overcommit(int bytes);
+extern void rx_emergency_put(int bytes);
+
+extern void sk_adjust_memalloc(int socks, int tx_reserve_pages);
+extern void skb_reserve_memory(int skb_reserve_bytes);
+extern void aux_reserve_memory(int aux_reserve_pages);
+extern int sk_set_vmio(struct sock *sk);
+extern int sk_clear_vmio(struct sock *sk);
+
 static inline void sk_acceptq_removed(struct sock *sk)
 {
 	sk->sk_ack_backlog--;
Index: linux-2.6-git/net/core/sock.c
===================================================================
--- linux-2.6-git.orig/net/core/sock.c	2007-02-20 15:06:17.000000000 +0100
+++ linux-2.6-git/net/core/sock.c	2007-02-20 15:18:48.000000000 +0100
@@ -112,6 +112,7 @@
 #include <linux/tcp.h>
 #include <linux/init.h>
 #include <linux/highmem.h>
+#include <linux/log2.h>
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -196,6 +197,138 @@ __u32 sysctl_rmem_default __read_mostly 
 /* Maximal space eaten by iovec or ancilliary data plus some space */
 int sysctl_optmem_max __read_mostly = sizeof(unsigned long)*(2*UIO_MAXIOV+512);
 
+static atomic_t rx_emergency_bytes;
+
+static int skb_reserve_bytes;
+static int aux_reserve_pages;
+
+static DEFINE_SPINLOCK(memalloc_lock);
+static int rx_net_reserve;
+atomic_t vmio_socks;
+EXPORT_SYMBOL_GPL(vmio_socks);
+
+/*
+ * is there room for another emergency packet?
+ * we account in power of two units to approx the slab allocator.
+ */
+static int __rx_emergency_get(int bytes, bool overcommit)
+{
+	int size = roundup_pow_of_two(bytes);
+	int nr = atomic_add_return(size, &rx_emergency_bytes);
+	int thresh = (3 * skb_reserve_bytes) / 2;
+	if (nr < thresh || overcommit)
+		return 1;
+
+	atomic_dec(&rx_emergency_bytes);
+	return 0;
+}
+
+int rx_emergency_get(int bytes)
+{
+	return __rx_emergency_get(bytes, false);
+}
+
+int rx_emergency_get_overcommit(int bytes)
+{
+	return __rx_emergency_get(bytes, true);
+}
+
+void rx_emergency_put(int bytes)
+{
+	int size = roundup_pow_of_two(bytes);
+	return atomic_sub(size, &rx_emergency_bytes);
+}
+
+/**
+ *	sk_adjust_memalloc - adjust the global memalloc reserve for critical RX
+ *	@socks: number of new %SOCK_VMIO sockets
+ *	@tx_resserve_pages: number of pages to (un)reserve for TX
+ *
+ *	This function adjusts the memalloc reserve based on system demand.
+ *	The RX reserve is a limit, and only added once, not for each socket.
+ *
+ *	NOTE:
+ *	   @tx_reserve_pages is an upper-bound of memory used for TX hence
+ *	   we need not account the pages like we do for RX pages.
+ */
+void sk_adjust_memalloc(int socks, int tx_reserve_pages)
+{
+	unsigned long flags;
+	int reserve = tx_reserve_pages;
+	int nr_socks;
+
+	spin_lock_irqsave(&memalloc_lock, flags);
+	nr_socks = atomic_add_return(socks, &vmio_socks);
+	BUG_ON(nr_socks < 0);
+
+	if (nr_socks) {
+		int skb_reserve_pages = skb_reserve_bytes / PAGE_SIZE;
+		int rx_pages = 2 * skb_reserve_pages + aux_reserve_pages;
+		reserve += rx_pages - rx_net_reserve;
+		rx_net_reserve = rx_pages;
+	} else {
+		reserve -= rx_net_reserve;
+		rx_net_reserve = 0;
+	}
+
+	if (reserve)
+		adjust_memalloc_reserve(reserve);
+	spin_unlock_irqrestore(&memalloc_lock, flags);
+}
+EXPORT_SYMBOL_GPL(sk_adjust_memalloc);
+
+/*
+ * tiny helper functions to track the memory reserves
+ * needed because of modular ipv6
+ */
+void skb_reserve_memory(int bytes)
+{
+	skb_reserve_bytes += bytes;
+	sk_adjust_memalloc(0, 0);
+}
+EXPORT_SYMBOL_GPL(skb_reserve_memory);
+
+void aux_reserve_memory(int pages)
+{
+	aux_reserve_pages += pages;
+	sk_adjust_memalloc(0, 0);
+}
+EXPORT_SYMBOL_GPL(aux_reserve_memory);
+
+/**
+ *	sk_set_vmio - sets %SOCK_VMIO
+ *	@sk: socket to set it on
+ *
+ *	Set %SOCK_VMIO on a socket and increase the memalloc reserve
+ *	accordingly.
+ */
+int sk_set_vmio(struct sock *sk)
+{
+	int set = sock_flag(sk, SOCK_VMIO);
+#ifndef CONFIG_NETVM
+	BUG();
+#endif
+	if (!set) {
+		sk_adjust_memalloc(1, 0);
+		sock_set_flag(sk, SOCK_VMIO);
+		sk->sk_allocation |= __GFP_EMERGENCY;
+	}
+	return !set;
+}
+EXPORT_SYMBOL_GPL(sk_set_vmio);
+
+int sk_clear_vmio(struct sock *sk)
+{
+	int set = sock_flag(sk, SOCK_VMIO);
+	if (set) {
+		sk_adjust_memalloc(-1, 0);
+		sock_reset_flag(sk, SOCK_VMIO);
+		sk->sk_allocation &= ~__GFP_EMERGENCY;
+	}
+	return set;
+}
+EXPORT_SYMBOL_GPL(sk_clear_vmio);
+
 static int sock_set_timeout(long *timeo_p, char __user *optval, int optlen)
 {
 	struct timeval tv;
@@ -868,6 +1001,7 @@ void sk_free(struct sock *sk)
 	struct sk_filter *filter;
 	struct module *owner = sk->sk_prot_creator->owner;
 
+	sk_clear_vmio(sk);
 	if (sk->sk_destruct)
 		sk->sk_destruct(sk);
 
Index: linux-2.6-git/net/Kconfig
===================================================================
--- linux-2.6-git.orig/net/Kconfig	2007-02-20 14:42:09.000000000 +0100
+++ linux-2.6-git/net/Kconfig	2007-02-20 15:06:17.000000000 +0100
@@ -227,6 +227,9 @@ config WIRELESS_EXT
 config FIB_RULES
 	bool
 
+config NETVM
+	def_bool n
+
 endif   # if NET
 endmenu # Networking
 

-- 

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