[PATCH 17/30] netvm: network reserve infrastructure

Peter Zijlstra
2008-03-20T20:28:31Z

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Provide the basic infrastructure to reserve and charge/account network memory.

We provide the following reserve tree:

1) total network reserve
2) network TX reserve
3) protocol TX pages
4) network RX reserve
5) SKB data reserve

[1] is used to make all the network reserves a single subtree, for easy
manipulation.

[2] and [4] are merely for eastetic reasons.

The TX pages reserve [3] is assumed bounded by it being the upper bound of
memory that can be used for sending pages (not quite true, but good enough)

The SKB reserve [5] is an aggregate reserve, which is used to charge SKB data
against in the fallback path.

The consumers for these reserves are sockets marked with:
SOCK_MEMALLOC

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@chello.nl>
---
include/net/sock.h | 43 ++++++++++++++++++++-
net/Kconfig | 3 +
net/core/sock.c | 107 +++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 152 insertions(+), 1 deletion(-)

Index: linux-2.6/include/net/sock.h
===================================================================
--- linux-2.6.orig/include/net/sock.h
+++ linux-2.6/include/net/sock.h
@@ -51,6 +51,7 @@
#include <linux/skbuff.h> /* struct sk_buff */
#include <linux/mm.h>
#include <linux/security.h>
+#include <linux/reserve.h>

#include <linux/filter.h>

@@ -406,6 +407,7 @@ enum sock_flags {
SOCK_RCVTSTAMPNS, /* %SO_TIMESTAMPNS setting */
SOCK_LOCALROUTE, /* route locally only, %SO_DONTROUTE setting */
SOCK_QUEUE_SHRUNK, /* write queue has been shrunk recently */
+ SOCK_MEMALLOC, /* the VM depends on us - make sure we're serviced */
};

static inline void sock_copy_flags(struct sock *nsk, struct sock *osk)
@@ -428,9 +430,48 @@ static inline int sock_flag(struct sock
return test_bit(flag, &sk->sk_flags);
}

+static inline int sk_has_memalloc(struct sock *sk)
+{
+ return sock_flag(sk, SOCK_MEMALLOC);
+}
+
+extern struct mem_reserve net_rx_reserve;
+extern struct mem_reserve net_skb_reserve;
+
+#ifdef CONFIG_NETVM
+/*
+ * Guestimate the per request queue TX upper bound.
+ *
+ * Max packet size is 64k, and we need to reserve that much since the data
+ * might need to bounce it. Double it to be on the safe side.
+ */
+#define TX_RESERVE_PAGES DIV_ROUND_UP(2*65536, PAGE_SIZE)
+
+extern int memalloc_socks;
+
+static inline int sk_memalloc_socks(void)
+{
+ return memalloc_socks;
+}
+
+extern int sk_adjust_memalloc(int socks, long tx_reserve_pages);
+extern int sk_set_memalloc(struct sock *sk);
+extern int sk_clear_memalloc(struct sock *sk);
+#else
+static inline int sk_memalloc_socks(void)
+{
+ return 0;
+}
+
+static inline int sk_clear_memalloc(struct sock *sk)
+{
+ return 0;
+}
+#endif
+
static inline gfp_t sk_allocation(struct sock *sk, gfp_t gfp_mask)
{
- return gfp_mask;
+ return gfp_mask | (sk->sk_allocation & __GFP_MEMALLOC);
}

static inline void sk_acceptq_removed(struct sock *sk)
Index: linux-2.6/net/core/sock.c
===================================================================
--- linux-2.6.orig/net/core/sock.c
+++ linux-2.6/net/core/sock.c
@@ -112,6 +112,7 @@
#include <linux/tcp.h>
#include <linux/init.h>
#include <linux/highmem.h>
+#include <linux/reserve.h>

#include <asm/uaccess.h>
#include <asm/system.h>
@@ -213,6 +214,105 @@ __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 struct mem_reserve net_reserve;
+struct mem_reserve net_rx_reserve;
+EXPORT_SYMBOL_GPL(net_rx_reserve); /* modular ipv6 only */
+struct mem_reserve net_skb_reserve;
+EXPORT_SYMBOL_GPL(net_skb_reserve); /* modular ipv6 only */
+static struct mem_reserve net_tx_reserve;
+static struct mem_reserve net_tx_pages;
+
+#ifdef CONFIG_NETVM
+static DEFINE_MUTEX(memalloc_socks_lock);
+int memalloc_socks;
+
+/**
+ * sk_adjust_memalloc - adjust the global memalloc reserve for critical RX
+ * @socks: number of new %SOCK_MEMALLOC 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.
+ */
+int sk_adjust_memalloc(int socks, long tx_reserve_pages)
+{
+ int err;
+
+ mutex_lock(&memalloc_socks_lock);
+ err = mem_reserve_pages_add(&net_tx_pages, tx_reserve_pages);
+ if (err)
+ goto unlock;
+
+ /*
+ * either socks is positive and we need to check for 0 -> !0
+ * transition and connect the reserve tree when we observe it.
+ */
+ if (!memalloc_socks && socks > 0) {
+ err = mem_reserve_connect(&net_reserve, &mem_reserve_root);
+ if (err) {
+ /*
+ * if we failed to connect the tree, undo the tx
+ * reserve so that failure has no side effects.
+ */
+ mem_reserve_pages_add(&net_tx_pages, -tx_reserve_pages);
+ goto unlock;
+ }
+ }
+ memalloc_socks += socks;
+ /*
+ * or socks is negative and we must observe the !0 -> 0 transition
+ * and disconnect the reserve tree.
+ */
+ if (!memalloc_socks && socks)
+ mem_reserve_disconnect(&net_reserve);
+
+unlock:
+ mutex_unlock(&memalloc_socks_lock);
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(sk_adjust_memalloc);
+
+/**
+ * sk_set_memalloc - sets %SOCK_MEMALLOC
+ * @sk: socket to set it on
+ *
+ * Set %SOCK_MEMALLOC on a socket and increase the memalloc reserve
+ * accordingly.
+ */
+int sk_set_memalloc(struct sock *sk)
+{
+ int set = sock_flag(sk, SOCK_MEMALLOC);
+
+ if (!set) {
+ int err = sk_adjust_memalloc(1, 0);
+ if (err)
+ return err;
+
+ sock_set_flag(sk, SOCK_MEMALLOC);
+ sk->sk_allocation |= __GFP_MEMALLOC;
+ }
+ return !set;
+}
+EXPORT_SYMBOL_GPL(sk_set_memalloc);
+
+int sk_clear_memalloc(struct sock *sk)
+{
+ int set = sock_flag(sk, SOCK_MEMALLOC);
+ if (set) {
+ sk_adjust_memalloc(-1, 0);
+ sock_reset_flag(sk, SOCK_MEMALLOC);
+ sk->sk_allocation &= ~__GFP_MEMALLOC;
+ }
+ return set;
+}
+EXPORT_SYMBOL_GPL(sk_clear_memalloc);
+#endif
+
static int sock_set_timeout(long *timeo_p, char __user *optval, int optlen)
{
struct timeval tv;
@@ -968,6 +1068,7 @@ void sk_free(struct sock *sk)
{
struct sk_filter *filter;

+ sk_clear_memalloc(sk);
if (sk->sk_destruct)
sk->sk_destruct(sk);

@@ -1095,6 +1196,12 @@ void __init sk_init(void)
sysctl_wmem_max = 131071;
sysctl_rmem_max = 131071;
}
+
+ mem_reserve_init(&net_reserve, "total network reserve", NULL);
+ mem_reserve_init(&net_rx_reserve, "network RX reserve", &net_reserve);
+ mem_reserve_init(&net_skb_reserve, "SKB data reserve", &net_rx_reserve);
+ mem_reserve_init(&net_tx_reserve, "network TX reserve", &net_reserve);
+ mem_reserve_init(&net_tx_pages, "protocol TX pages", &net_tx_reserve);
}

/*
Index: linux-2.6/net/Kconfig
===================================================================
--- linux-2.6.orig/net/Kconfig
+++ linux-2.6/net/Kconfig
@@ -250,6 +250,9 @@ endmenu
source "net/rfkill/Kconfig"
source "net/9p/Kconfig"

+config NETVM
+ def_bool n
+
endif # if NET
endmenu # Networking

--