Fix O(n^2) behavior in sysctl
Sysctl OIDs were internally stored in linked lists, triggering O(n^2) behavior when userland iterates over many of them. The slowdown is noticeable for MIBs that have > 100 children (for example, vm.uma). But it's unignorable for kstat.zfs when a pool has > 1000 datasets. Convert the linked lists into RB trees. This produces a ~25x speedup for listing kstat.zfs with 4100 datasets, and no measurable penalty for small dataset counts. Bump __FreeBSD_version for the KPI change. Sponsored by: Axcient Reviewed by: mjg Differential Revision: https://reviews.freebsd.org/D36500
This commit is contained in:
Alan Somers
parent
cee4fc7cad
commit
d3f96f6610
@ -246,7 +246,7 @@ sysfs_unmerge_group(struct kobject *kobj, const struct attribute_group *grp)
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struct attribute **attr;
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struct sysctl_oid *oidp;
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SLIST_FOREACH(oidp, SYSCTL_CHILDREN(kobj->oidp), oid_link) {
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RB_FOREACH(oidp, sysctl_oid_list, SYSCTL_CHILDREN(kobj->oidp)) {
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if (strcmp(oidp->oid_name, grp->name) != 0)
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continue;
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for (attr = grp->attrs; *attr != NULL; attr++) {
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@ -84,6 +84,8 @@ static MALLOC_DEFINE(M_SYSCTL, "sysctl", "sysctl internal magic");
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static MALLOC_DEFINE(M_SYSCTLOID, "sysctloid", "sysctl dynamic oids");
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static MALLOC_DEFINE(M_SYSCTLTMP, "sysctltmp", "sysctl temp output buffer");
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RB_GENERATE(sysctl_oid_list, sysctl_oid, oid_link, cmp_sysctl_oid);
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/*
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* The sysctllock protects the MIB tree. It also protects sysctl
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* contexts used with dynamic sysctls. The sysctl_register_oid() and
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@ -120,7 +122,7 @@ static struct sx sysctlstringlock;
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static int sysctl_root(SYSCTL_HANDLER_ARGS);
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/* Root list */
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struct sysctl_oid_list sysctl__children = SLIST_HEAD_INITIALIZER(&sysctl__children);
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struct sysctl_oid_list sysctl__children = RB_INITIALIZER(&sysctl__children);
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static char* sysctl_escape_name(const char*);
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static int sysctl_remove_oid_locked(struct sysctl_oid *oidp, int del,
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@ -134,7 +136,7 @@ sysctl_find_oidname(const char *name, struct sysctl_oid_list *list)
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struct sysctl_oid *oidp;
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SYSCTL_ASSERT_LOCKED();
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SLIST_FOREACH(oidp, list, oid_link) {
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RB_FOREACH(oidp, sysctl_oid_list, list) {
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if (strcmp(oidp->oid_name, name) == 0) {
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return (oidp);
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}
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@ -356,11 +358,14 @@ sysctl_search_oid(struct sysctl_oid **nodes, struct sysctl_oid *needle)
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indx = 0;
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while (indx < CTL_MAXNAME && indx >= 0) {
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if (nodes[indx] == NULL && indx == 0)
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nodes[indx] = SLIST_FIRST(&sysctl__children);
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nodes[indx] = RB_MIN(sysctl_oid_list,
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&sysctl__children);
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else if (nodes[indx] == NULL)
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nodes[indx] = SLIST_FIRST(&nodes[indx - 1]->oid_children);
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nodes[indx] = RB_MIN(sysctl_oid_list,
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&nodes[indx - 1]->oid_children);
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else
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nodes[indx] = SLIST_NEXT(nodes[indx], oid_link);
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nodes[indx] = RB_NEXT(sysctl_oid_list,
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&nodes[indx - 1]->oid_children, nodes[indx]);
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if (nodes[indx] == needle)
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return (indx + 1);
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@ -425,8 +430,7 @@ void
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sysctl_register_oid(struct sysctl_oid *oidp)
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{
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struct sysctl_oid_list *parent = oidp->oid_parent;
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struct sysctl_oid *p;
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struct sysctl_oid *q;
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struct sysctl_oid *p, key;
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int oid_number;
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int timeout = 2;
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@ -476,25 +480,21 @@ sysctl_register_oid(struct sysctl_oid *oidp)
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* Insert the OID into the parent's list sorted by OID number.
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*/
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retry:
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q = NULL;
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SLIST_FOREACH(p, parent, oid_link) {
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/* check if the current OID number is in use */
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if (oid_number == p->oid_number) {
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/* get the next valid OID number */
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if (oid_number < CTL_AUTO_START ||
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oid_number == 0x7fffffff) {
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/* wraparound - restart */
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oid_number = CTL_AUTO_START;
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/* don't loop forever */
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if (!timeout--)
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panic("sysctl: Out of OID numbers\n");
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goto retry;
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} else {
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oid_number++;
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}
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} else if (oid_number < p->oid_number)
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break;
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q = p;
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key.oid_number = oid_number;
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p = RB_FIND(sysctl_oid_list, parent, &key);
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if (p) {
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/* get the next valid OID number */
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if (oid_number < CTL_AUTO_START ||
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oid_number == 0x7fffffff) {
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/* wraparound - restart */
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oid_number = CTL_AUTO_START;
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/* don't loop forever */
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if (!timeout--)
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panic("sysctl: Out of OID numbers\n");
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goto retry;
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} else {
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oid_number++;
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}
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}
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/* check for non-auto OID number collision */
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if (oidp->oid_number >= 0 && oidp->oid_number < CTL_AUTO_START &&
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@ -504,10 +504,7 @@ sysctl_register_oid(struct sysctl_oid *oidp)
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}
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/* update the OID number, if any */
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oidp->oid_number = oid_number;
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if (q != NULL)
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SLIST_INSERT_AFTER(q, oidp, oid_link);
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else
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SLIST_INSERT_HEAD(parent, oidp, oid_link);
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RB_INSERT(sysctl_oid_list, parent, oidp);
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if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE &&
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#ifdef VIMAGE
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@ -556,7 +553,6 @@ sysctl_enable_oid(struct sysctl_oid *oidp)
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void
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sysctl_unregister_oid(struct sysctl_oid *oidp)
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{
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struct sysctl_oid *p;
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int error;
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SYSCTL_ASSERT_WLOCKED();
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@ -564,14 +560,8 @@ sysctl_unregister_oid(struct sysctl_oid *oidp)
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error = EINVAL;
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} else {
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error = ENOENT;
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SLIST_FOREACH(p, oidp->oid_parent, oid_link) {
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if (p == oidp) {
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SLIST_REMOVE(oidp->oid_parent, oidp,
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sysctl_oid, oid_link);
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error = 0;
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break;
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}
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}
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if (RB_REMOVE(sysctl_oid_list, oidp->oid_parent, oidp))
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error = 0;
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}
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/*
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@ -732,17 +722,14 @@ int
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sysctl_remove_name(struct sysctl_oid *parent, const char *name,
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int del, int recurse)
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{
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struct sysctl_oid *p, *tmp;
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struct sysctl_oid *p;
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int error;
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error = ENOENT;
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SYSCTL_WLOCK();
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SLIST_FOREACH_SAFE(p, SYSCTL_CHILDREN(parent), oid_link, tmp) {
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if (strcmp(p->oid_name, name) == 0) {
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error = sysctl_remove_oid_locked(p, del, recurse);
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break;
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}
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}
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p = sysctl_find_oidname(name, &parent->oid_children);
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if (p)
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error = sysctl_remove_oid_locked(p, del, recurse);
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SYSCTL_WUNLOCK();
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return (error);
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@ -811,14 +798,16 @@ sysctl_remove_oid_locked(struct sysctl_oid *oidp, int del, int recurse)
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*/
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if ((oidp->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
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if (oidp->oid_refcnt == 1) {
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SLIST_FOREACH_SAFE(p,
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SYSCTL_CHILDREN(oidp), oid_link, tmp) {
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for(p = RB_MIN(sysctl_oid_list, &oidp->oid_children);
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p != NULL; p = tmp) {
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if (!recurse) {
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printf("Warning: failed attempt to "
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"remove oid %s with child %s\n",
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oidp->oid_name, p->oid_name);
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return (ENOTEMPTY);
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}
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tmp = RB_NEXT(sysctl_oid_list,
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&oidp->oid_children, p);
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error = sysctl_remove_oid_locked(p, del,
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recurse);
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if (error)
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@ -895,7 +884,7 @@ sysctl_add_oid(struct sysctl_ctx_list *clist, struct sysctl_oid_list *parent,
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}
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oidp = malloc(sizeof(struct sysctl_oid), M_SYSCTLOID, M_WAITOK|M_ZERO);
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oidp->oid_parent = parent;
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SLIST_INIT(&oidp->oid_children);
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RB_INIT(&oidp->oid_children);
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oidp->oid_number = number;
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oidp->oid_refcnt = 1;
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oidp->oid_name = escaped;
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@ -1016,7 +1005,7 @@ sysctl_sysctl_debug_dump_node(struct sysctl_oid_list *l, int i)
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struct sysctl_oid *oidp;
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SYSCTL_ASSERT_LOCKED();
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SLIST_FOREACH(oidp, l, oid_link) {
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RB_FOREACH(oidp, sysctl_oid_list, l) {
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for (k=0; k<i; k++)
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printf(" ");
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@ -1081,7 +1070,7 @@ sysctl_sysctl_name(SYSCTL_HANDLER_ARGS)
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int *name = (int *) arg1;
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u_int namelen = arg2;
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int error;
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struct sysctl_oid *oid;
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struct sysctl_oid *oid, key;
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struct sysctl_oid_list *lsp = &sysctl__children, *lsp2;
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struct rm_priotracker tracker;
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char buf[10];
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@ -1105,10 +1094,9 @@ sysctl_sysctl_name(SYSCTL_HANDLER_ARGS)
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continue;
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}
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lsp2 = NULL;
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SLIST_FOREACH(oid, lsp, oid_link) {
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if (oid->oid_number != *name)
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continue;
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key.oid_number = *name;
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oid = RB_FIND(sysctl_oid_list, lsp, &key);
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if (oid) {
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if (req->oldidx)
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error = SYSCTL_OUT(req, ".", 1);
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if (!error)
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@ -1120,14 +1108,9 @@ sysctl_sysctl_name(SYSCTL_HANDLER_ARGS)
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namelen--;
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name++;
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if ((oid->oid_kind & CTLTYPE) != CTLTYPE_NODE)
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break;
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if (oid->oid_handler)
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break;
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lsp2 = SYSCTL_CHILDREN(oid);
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break;
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if ((oid->oid_kind & CTLTYPE) == CTLTYPE_NODE &&
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!oid->oid_handler)
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lsp2 = SYSCTL_CHILDREN(oid);
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}
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lsp = lsp2;
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}
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@ -1239,13 +1222,25 @@ static bool
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sysctl_sysctl_next_action(struct sysctl_oid_list *lsp, int *name, u_int namelen,
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int *next, int *len, int level, bool honor_skip)
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{
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struct sysctl_oid *oidp;
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struct sysctl_oid_list *next_lsp;
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struct sysctl_oid *oidp = NULL, key;
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bool success = false;
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enum sysctl_iter_action action;
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SYSCTL_ASSERT_LOCKED();
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SLIST_FOREACH(oidp, lsp, oid_link) {
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action = sysctl_sysctl_next_node(oidp, name, namelen, honor_skip);
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/*
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* Start the search at the requested oid. But if not found, then scan
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* through all children.
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*/
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if (namelen > 0) {
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key.oid_number = *name;
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oidp = RB_FIND(sysctl_oid_list, lsp, &key);
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}
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if (!oidp)
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oidp = RB_MIN(sysctl_oid_list, lsp);
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for(; oidp != NULL; oidp = RB_NEXT(sysctl_oid_list, lsp, oidp)) {
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action = sysctl_sysctl_next_node(oidp, name, namelen,
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honor_skip);
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if (action == ITER_SIBLINGS)
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continue;
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if (action == ITER_FOUND) {
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@ -1254,13 +1249,13 @@ sysctl_sysctl_next_action(struct sysctl_oid_list *lsp, int *name, u_int namelen,
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}
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KASSERT((action== ITER_CHILDREN), ("ret(%d)!=ITER_CHILDREN", action));
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lsp = SYSCTL_CHILDREN(oidp);
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next_lsp = SYSCTL_CHILDREN(oidp);
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if (namelen == 0) {
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success = sysctl_sysctl_next_action(lsp, NULL, 0,
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success = sysctl_sysctl_next_action(next_lsp, NULL, 0,
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next + 1, len, level + 1, honor_skip);
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} else {
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success = sysctl_sysctl_next_action(lsp, name + 1, namelen - 1,
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next + 1, len, level + 1, honor_skip);
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success = sysctl_sysctl_next_action(next_lsp, name + 1,
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namelen - 1, next + 1, len, level + 1, honor_skip);
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if (!success) {
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/*
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@ -1332,13 +1327,12 @@ name2oid(char *name, int *oid, int *len, struct sysctl_oid **oidpp)
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for (*len = 0; *len < CTL_MAXNAME;) {
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p = strsep(&name, ".");
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oidp = SLIST_FIRST(lsp);
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for (;; oidp = SLIST_NEXT(oidp, oid_link)) {
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if (oidp == NULL)
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return (ENOENT);
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RB_FOREACH(oidp, sysctl_oid_list, lsp) {
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if (strcmp(p, oidp->oid_name) == 0)
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break;
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}
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if (oidp == NULL)
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return (ENOENT);
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*oid++ = oidp->oid_number;
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(*len)++;
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@ -2162,16 +2156,15 @@ sysctl_find_oid(int *name, u_int namelen, struct sysctl_oid **noid,
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{
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struct sysctl_oid_list *lsp;
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struct sysctl_oid *oid;
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struct sysctl_oid key;
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int indx;
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SYSCTL_ASSERT_LOCKED();
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lsp = &sysctl__children;
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indx = 0;
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while (indx < CTL_MAXNAME) {
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SLIST_FOREACH(oid, lsp, oid_link) {
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if (oid->oid_number == name[indx])
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break;
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}
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key.oid_number = name[indx];
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oid = RB_FIND(sysctl_oid_list, lsp, &key);
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if (oid == NULL)
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return (ENOENT);
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@ -525,7 +525,7 @@ vfs_register(struct vfsconf *vfc)
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* number.
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*/
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sysctl_wlock();
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SLIST_FOREACH(oidp, SYSCTL_CHILDREN(&sysctl___vfs), oid_link) {
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RB_FOREACH(oidp, sysctl_oid_list, SYSCTL_CHILDREN(&sysctl___vfs)) {
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if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
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sysctl_unregister_oid(oidp);
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oidp->oid_number = vfc->vfc_typenum;
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@ -76,7 +76,7 @@
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* cannot include sys/param.h and should only be updated here.
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*/
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#undef __FreeBSD_version
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#define __FreeBSD_version 1400070
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#define __FreeBSD_version 1400071
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/*
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* __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,
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@ -39,7 +39,8 @@
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#define _SYS_SYSCTL_H_
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#ifdef _KERNEL
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#include <sys/queue.h>
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#include <sys/tree.h>
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#include <sys/systm.h>
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#endif
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/*
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@ -173,20 +174,25 @@ struct sysctl_req {
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int flags;
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};
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SLIST_HEAD(sysctl_oid_list, sysctl_oid);
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struct sysctl_oid;
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/* RB Tree handling */
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RB_HEAD(sysctl_oid_list, sysctl_oid);
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/*
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* This describes one "oid" in the MIB tree. Potentially more nodes can
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* be hidden behind it, expanded by the handler.
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*/
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struct sysctl_oid {
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struct sysctl_oid_list oid_children;
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struct sysctl_oid_list *oid_parent;
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SLIST_ENTRY(sysctl_oid) oid_link;
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struct sysctl_oid_list oid_children;
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struct sysctl_oid_list* oid_parent;
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RB_ENTRY(sysctl_oid) oid_link;
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/* Sort key for all siblings, and lookup key for userland */
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int oid_number;
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u_int oid_kind;
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void *oid_arg1;
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intmax_t oid_arg2;
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/* Must be unique amongst all siblings. */
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const char *oid_name;
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int (*oid_handler)(SYSCTL_HANDLER_ARGS);
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const char *oid_fmt;
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@ -196,6 +202,19 @@ struct sysctl_oid {
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const char *oid_label;
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};
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static inline int
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cmp_sysctl_oid(struct sysctl_oid *a, struct sysctl_oid *b)
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{
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if (a->oid_number > b->oid_number)
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return (1);
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else if (a->oid_number < b->oid_number)
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return (-1);
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else
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return (0);
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}
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RB_PROTOTYPE(sysctl_oid_list, sysctl_oid, oid_link, cmp_sysctl_oid);
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#define SYSCTL_IN(r, p, l) (r->newfunc)(r, p, l)
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#define SYSCTL_OUT(r, p, l) (r->oldfunc)(r, p, l)
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#define SYSCTL_OUT_STR(r, p) (r->oldfunc)(r, p, strlen(p) + 1)
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@ -275,7 +294,7 @@ TAILQ_HEAD(sysctl_ctx_list, sysctl_ctx_entry);
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#define SYSCTL_OID_RAW(id, parent_child_head, nbr, name, kind, a1, a2, handler, fmt, descr, label) \
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struct sysctl_oid id = { \
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.oid_parent = (parent_child_head), \
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.oid_children = SLIST_HEAD_INITIALIZER(&id.oid_children), \
|
||||
.oid_children = RB_INITIALIZER(&id.oid_children), \
|
||||
.oid_number = (nbr), \
|
||||
.oid_kind = (kind), \
|
||||
.oid_arg1 = (a1), \
|
||||
|
||||
Loading…
Reference in New Issue
Block a user