provide a custom pool page allocator for mbufs, but dont use it yet.

the custom allocator is basically a wrapper around the multi page
pool allocator, but it has a single global memory limit managed by
the wrapper.

currently each of the mbuf pools has their own memory limit (or
none in the case of the myx pool) independent of the other pools.
this means each pool can allocate up to nmbclust worth of mbufs,
rather than all of them sharing the one limit. wrapping the allocator
like this means we can move to a single memory limit for all mbufs
in the system.

ok bluhm@ as part of a larger diff

1 files changed, 57 insertions, 1 deletions

diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index 2ef5c139c95..94176d309f6 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uipc_mbuf.c,v 1.241 2017/02/05 16:23:38 jca Exp $	*/
+/*	$OpenBSD: uipc_mbuf.c,v 1.242 2017/02/07 06:21:37 dlg Exp $	*/
 /*	$NetBSD: uipc_mbuf.c,v 1.15.4.1 1996/06/13 17:11:44 cgd Exp $	*/
 
 /*
@@ -133,6 +133,19 @@ void	m_extfree(struct mbuf *);
 void	nmbclust_update(void);
 void	m_zero(struct mbuf *);
 
+struct mutex m_pool_mtx = MUTEX_INITIALIZER(IPL_NET);
+unsigned int mbuf_mem_limit; /* how much memory can be allocated */
+unsigned int mbuf_mem_alloc; /* how much memory has been allocated */
+
+void	*m_pool_alloc(struct pool *, int, int *);
+void	m_pool_free(struct pool *, void *);
+
+struct pool_allocator m_pool_allocator = {
+	m_pool_alloc,
+	m_pool_free,
+	0 /* will be copied from pool_allocator_multi */
+};
+
 static void (*mextfree_fns[4])(caddr_t, u_int, void *);
 static u_int num_extfree_fns;
 
@@ -148,6 +161,8 @@ mbinit(void)
 	int i;
 	unsigned int lowbits;
 
+	m_pool_allocator.pa_pagesz = pool_allocator_multi.pa_pagesz;
+
 #if DIAGNOSTIC
 	if (mclsizes[0] != MCLBYTES)
 		panic("mbinit: the smallest cluster size != MCLBYTES");
@@ -212,6 +227,8 @@ nmbclust_update(void)
 		pool_sethiwat(&mclpools[i], n);
 	}
 	pool_sethiwat(&mbpool, nmbclust);
+
+	mbuf_mem_limit = nmbclust * MCLBYTES;
 }
 
 /*
@@ -1386,6 +1403,45 @@ fail:
 	return (NULL);
 }
 
+void *
+m_pool_alloc(struct pool *pp, int flags, int *slowdown)
+{
+	void *v = NULL;
+	int avail = 1;
+
+	if (mbuf_mem_alloc + pp->pr_pgsize > mbuf_mem_limit)
+		return (NULL);
+
+	mtx_enter(&m_pool_mtx);
+	if (mbuf_mem_alloc + pp->pr_pgsize > mbuf_mem_limit)
+		avail = 0;
+	else
+		mbuf_mem_alloc += pp->pr_pgsize;
+	mtx_leave(&m_pool_mtx);
+
+	if (avail) {
+		v = (*pool_allocator_multi.pa_alloc)(pp, flags, slowdown);
+
+		if (v == NULL) {
+			mtx_enter(&m_pool_mtx);
+			mbuf_mem_alloc -= pp->pr_pgsize;
+			mtx_leave(&m_pool_mtx);
+		}
+	}
+
+	return (v);
+}
+
+void
+m_pool_free(struct pool *pp, void *v)
+{
+	(*pool_allocator_multi.pa_free)(pp, v);
+
+	mtx_enter(&m_pool_mtx);
+	mbuf_mem_alloc -= pp->pr_pgsize;
+	mtx_leave(&m_pool_mtx);
+}
+
 #ifdef DDB
 void
 m_print(void *v,