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vfs: only recalculate watermarks when limits are changing

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Previously they would get recalculated all the time, in particular in:
getnewvnode -> vcheckspace -> vspace
This commit is contained in:
Mateusz Guzik 2020-01-11 23:00:57 +00:00
parent e6ae744e0e
commit 91de98e6d4
1 changed files with 66 additions and 17 deletions
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77
sys/kern/vfs_subr.c
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@ -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 expansion */
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) {
if (val == desiredvnodes)
return (0);
mtx_lock(&vnode_free_list_mtx);
desiredvnodes = val;
wantfreevnodes = desiredvnodes / 4;
/* XXX locking seems to be incomplete. */
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),
@ -1211,6 +1254,15 @@ 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
@ -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)