diff options
| author | Alexander Bluhm <bluhm@cvs.openbsd.org> | 2024-11-06 14:37:46 +0000 |
|---|---|---|
| committer | Alexander Bluhm <bluhm@cvs.openbsd.org> | 2024-11-06 14:37:46 +0000 |
| commit | be67c1623e5cff64b38112356f5fa4175040881d (patch) | |
| tree | dd13dc0c7b0d8a5c83c84c794ffb7e2497fff924 /sys/kern | |
| parent | 98e8bc8aba248755245c6d81042ae5eeec1f45b9 (diff) | |
Use atomic load and store operations for sbchecklowmem().
Use atomic operations to make explicit where access from multiple
CPU happens. Add a comment why sbchecklowmem() is sufficently MP
safe without locks.
OK mvs@ claudio@
Diffstat (limited to 'sys/kern')
| -rw-r--r-- | sys/kern/uipc_mbuf.c | 14 | ||||
| -rw-r--r-- | sys/kern/uipc_socket2.c | 16 |
2 files changed, 19 insertions, 11 deletions
diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c index 34ce9390635..1151a179fb5 100644 --- a/sys/kern/uipc_mbuf.c +++ b/sys/kern/uipc_mbuf.c @@ -1,4 +1,4 @@ -/* $OpenBSD: uipc_mbuf.c,v 1.294 2024/09/10 14:52:42 bluhm Exp $ */ +/* $OpenBSD: uipc_mbuf.c,v 1.295 2024/11/06 14:37:45 bluhm Exp $ */ /* $NetBSD: uipc_mbuf.c,v 1.15.4.1 1996/06/13 17:11:44 cgd Exp $ */ /* @@ -129,8 +129,8 @@ struct mutex m_extref_mtx = MUTEX_INITIALIZER(IPL_NET); void m_extfree(struct mbuf *); void m_zero(struct mbuf *); -unsigned long mbuf_mem_limit; /* how much memory can be allocated */ -unsigned long mbuf_mem_alloc; /* how much memory has been allocated */ +unsigned long mbuf_mem_limit; /* [a] how much memory can be allocated */ +unsigned long mbuf_mem_alloc; /* [a] how much memory has been allocated */ void *m_pool_alloc(struct pool *, int, int *); void m_pool_free(struct pool *, void *); @@ -219,7 +219,7 @@ nmbclust_update(long newval) return ERANGE; /* update the global mbuf memory limit */ nmbclust = newval; - mbuf_mem_limit = nmbclust * MCLBYTES; + atomic_store_long(&mbuf_mem_limit, nmbclust * MCLBYTES); pool_wakeup(&mbpool); for (i = 0; i < nitems(mclsizes); i++) @@ -1458,7 +1458,8 @@ m_pool_alloc(struct pool *pp, int flags, int *slowdown) { void *v; - if (atomic_add_long_nv(&mbuf_mem_alloc, pp->pr_pgsize) > mbuf_mem_limit) + if (atomic_add_long_nv(&mbuf_mem_alloc, pp->pr_pgsize) > + atomic_load_long(&mbuf_mem_limit)) goto fail; v = (*pool_allocator_multi.pa_alloc)(pp, flags, slowdown); @@ -1488,7 +1489,8 @@ m_pool_init(struct pool *pp, u_int size, u_int align, const char *wmesg) u_int m_pool_used(void) { - return ((mbuf_mem_alloc * 100) / mbuf_mem_limit); + return ((atomic_load_long(&mbuf_mem_alloc) * 100) / + atomic_load_long(&mbuf_mem_limit)); } #ifdef DDB diff --git a/sys/kern/uipc_socket2.c b/sys/kern/uipc_socket2.c index 2855feb61c7..91f32710478 100644 --- a/sys/kern/uipc_socket2.c +++ b/sys/kern/uipc_socket2.c @@ -1,4 +1,4 @@ -/* $OpenBSD: uipc_socket2.c,v 1.158 2024/07/12 19:50:35 bluhm Exp $ */ +/* $OpenBSD: uipc_socket2.c,v 1.159 2024/11/06 14:37:45 bluhm Exp $ */ /* $NetBSD: uipc_socket2.c,v 1.11 1996/02/04 02:17:55 christos Exp $ */ /* @@ -684,14 +684,20 @@ int sbchecklowmem(void) { static int sblowmem; - unsigned int used = m_pool_used(); + unsigned int used; + /* + * m_pool_used() is thread safe. Global variable sblowmem is updated + * by multiple CPUs, but most times with the same value. And even + * if the value is not correct for a short time, it does not matter. + */ + used = m_pool_used(); if (used < 60) - sblowmem = 0; + atomic_store_int(&sblowmem, 0); else if (used > 80) - sblowmem = 1; + atomic_store_int(&sblowmem, 1); - return (sblowmem); + return (atomic_load_int(&sblowmem)); } /* |