Author: mjg
Date: Sat Jan 11 23:00:57 2020
New Revision: 356645
URL: https://svnweb.freebsd.org/changeset/base/356645
Log:
vfs: only recalculate watermarks when limits are changing
Previously they would get recalculated all the time, in particular in:
getnewvnode -> vcheckspace -> vspace
Modified:
head/sys/kern/vfs_subr.c
Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c Sat Jan 11 22:59:44 2020 (r356644)
+++ head/sys/kern/vfs_subr.c Sat Jan 11 23:00:57 2020 (r356645)
@@ -118,6 +118,7 @@ static void vnlru_return_batches(struct vfsops *mnt_op
static void destroy_vpollinfo(struct vpollinfo *vi);
static int v_inval_buf_range_locked(struct vnode *vp, struct bufobj *bo,
daddr_t startlbn, daddr_t endlbn);
+static void vnlru_recalc(void);
/*
* These fences are intended for cases where some synchronization is
@@ -194,8 +195,6 @@ static TAILQ_HEAD(freelst, vnode) vnode_free_list;
* whenever vnlru_proc() becomes active.
*/
static u_long wantfreevnodes;
-SYSCTL_ULONG(_vfs, OID_AUTO, wantfreevnodes, CTLFLAG_RW,
- &wantfreevnodes, 0, "Target for minimum number of \"free\" vnodes");
static u_long freevnodes;
SYSCTL_ULONG(_vfs, OID_AUTO, freevnodes, CTLFLAG_RD,
&freevnodes, 0, "Number of \"free\" vnodes");
@@ -317,27 +316,65 @@ static u_long vlowat; /* minimal extras
before expans
static u_long vstir; /* nonzero to stir non-free vnodes */
static volatile int vsmalltrigger = 8; /* pref to keep if > this many pages */
+/*
+ * Note that no attempt is made to sanitize these parameters.
+ */
static int
-sysctl_update_desiredvnodes(SYSCTL_HANDLER_ARGS)
+sysctl_maxvnodes(SYSCTL_HANDLER_ARGS)
{
- u_long old_desiredvnodes;
+ u_long val;
int error;
- old_desiredvnodes = desiredvnodes;
- if ((error = sysctl_handle_long(oidp, arg1, arg2, req)) != 0)
+ val = desiredvnodes;
+ error = sysctl_handle_long(oidp, &val, 0, req);
+ if (error != 0 || req->newptr == NULL)
return (error);
- if (old_desiredvnodes != desiredvnodes) {
- wantfreevnodes = desiredvnodes / 4;
- /* XXX locking seems to be incomplete. */
- vfs_hash_changesize(desiredvnodes);
- cache_changesize(desiredvnodes);
- }
+
+ if (val == desiredvnodes)
+ return (0);
+ mtx_lock(&vnode_free_list_mtx);
+ desiredvnodes = val;
+ wantfreevnodes = desiredvnodes / 4;
+ vnlru_recalc();
+ mtx_unlock(&vnode_free_list_mtx);
+ /*
+ * XXX There is no protection against multiple threads changing
+ * desiredvnodes at the same time. Locking above only helps vnlru and
+ * getnewvnode.
+ */
+ vfs_hash_changesize(desiredvnodes);
+ cache_changesize(desiredvnodes);
return (0);
}
SYSCTL_PROC(_kern, KERN_MAXVNODES, maxvnodes,
- CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_RW, &desiredvnodes, 0,
- sysctl_update_desiredvnodes, "UL", "Target for maximum number of vnodes");
+ CTLTYPE_ULONG | CTLFLAG_MPSAFE | CTLFLAG_RW, NULL, 0, sysctl_maxvnodes,
+ "UL", "Target for maximum number of vnodes");
+
+static int
+sysctl_wantfreevnodes(SYSCTL_HANDLER_ARGS)
+{
+ u_long val;
+ int error;
+
+ val = wantfreevnodes;
+ error = sysctl_handle_long(oidp, &val, 0, req);
+ if (error != 0 || req->newptr == NULL)
+ return (error);
+
+ if (val == wantfreevnodes)
+ return (0);
+ mtx_lock(&vnode_free_list_mtx);
+ wantfreevnodes = val;
+ vnlru_recalc();
+ mtx_unlock(&vnode_free_list_mtx);
+ return (0);
+}
+
+SYSCTL_PROC(_vfs, OID_AUTO, wantfreevnodes,
+ CTLTYPE_ULONG | CTLFLAG_MPSAFE | CTLFLAG_RW, NULL, 0,
sysctl_wantfreevnodes,
+ "UL", "Target for minimum number of \"free\" vnodes");
+
SYSCTL_ULONG(_kern, OID_AUTO, minvnodes, CTLFLAG_RW,
&wantfreevnodes, 0, "Old name for vfs.wantfreevnodes (legacy)");
static int vnlru_nowhere;
@@ -591,6 +628,12 @@ vntblinit(void *dummy __unused)
mtx_init(&mntid_mtx, "mntid", NULL, MTX_DEF);
TAILQ_INIT(&vnode_free_list);
mtx_init(&vnode_free_list_mtx, "vnode_free_list", NULL, MTX_DEF);
+ /*
+ * The lock is taken to appease WITNESS.
+ */
+ mtx_lock(&vnode_free_list_mtx);
+ vnlru_recalc();
+ mtx_unlock(&vnode_free_list_mtx);
vnode_zone = uma_zcreate("VNODE", sizeof (struct vnode), NULL, NULL,
vnode_init, vnode_fini, UMA_ALIGN_PTR, 0);
vnodepoll_zone = uma_zcreate("VNODEPOLL", sizeof (struct vpollinfo),
@@ -1211,7 +1254,16 @@ vnlru_free(int count, struct vfsops *mnt_op)
mtx_unlock(&vnode_free_list_mtx);
}
+static void
+vnlru_recalc(void)
+{
+ mtx_assert(&vnode_free_list_mtx, MA_OWNED);
+ gapvnodes = imax(desiredvnodes - wantfreevnodes, 100);
+ vhiwat = gapvnodes / 11; /* 9% -- just under the 10% in vlrureclaim() */
+ vlowat = vhiwat / 2;
+}
+
/* XXX some names and initialization are bad for limits and watermarks. */
static int
vspace(void)
@@ -1219,9 +1271,6 @@ vspace(void)
u_long rnumvnodes, rfreevnodes;
int space;
- gapvnodes = imax(desiredvnodes - wantfreevnodes, 100);
- vhiwat = gapvnodes / 11; /* 9% -- just under the 10% in vlrureclaim() */
- vlowat = vhiwat / 2;
rnumvnodes = atomic_load_long(&numvnodes);
rfreevnodes = atomic_load_long(&freevnodes);
if (rnumvnodes > desiredvnodes)
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