sync_vnode() has some messy code about locking in order to deal with
mount fs needing Giant to be held when processing bufobjs. Use a different subqueue for pending workitems on filesystems requiring Giant. This simplifies the code notably and also reduces the number of Giant acquisitions (and the whole processing cost). Suggested by: jeff Reviewed by: kib Tested by: pho
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attilio
parent
30e27ea7fd
commit
bb68298f62
@ -89,6 +89,9 @@ __FBSDID("$FreeBSD$");
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#include <ddb/ddb.h>
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#endif
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#define WI_MPSAFEQ 0
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#define WI_GIANTQ 1
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static MALLOC_DEFINE(M_NETADDR, "subr_export_host", "Export host address structure");
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static void delmntque(struct vnode *vp);
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@ -221,7 +224,7 @@ int prtactive;
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static int syncer_delayno;
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static long syncer_mask;
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LIST_HEAD(synclist, bufobj);
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static struct synclist *syncer_workitem_pending;
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static struct synclist *syncer_workitem_pending[2];
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/*
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* The sync_mtx protects:
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* bo->bo_synclist
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@ -317,8 +320,10 @@ vntblinit(void *dummy __unused)
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/*
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* Initialize the filesystem syncer.
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*/
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syncer_workitem_pending = hashinit(syncer_maxdelay, M_VNODE,
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&syncer_mask);
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syncer_workitem_pending[WI_MPSAFEQ] = hashinit(syncer_maxdelay, M_VNODE,
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&syncer_mask);
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syncer_workitem_pending[WI_GIANTQ] = hashinit(syncer_maxdelay, M_VNODE,
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&syncer_mask);
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syncer_maxdelay = syncer_mask + 1;
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mtx_init(&sync_mtx, "Syncer mtx", NULL, MTX_DEF);
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}
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@ -1568,7 +1573,7 @@ brelvp(struct buf *bp)
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static void
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vn_syncer_add_to_worklist(struct bufobj *bo, int delay)
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{
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int slot;
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int queue, slot;
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ASSERT_BO_LOCKED(bo);
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@ -1584,7 +1589,10 @@ vn_syncer_add_to_worklist(struct bufobj *bo, int delay)
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delay = syncer_maxdelay - 2;
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slot = (syncer_delayno + delay) & syncer_mask;
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LIST_INSERT_HEAD(&syncer_workitem_pending[slot], bo, bo_synclist);
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queue = VFS_NEEDSGIANT(bo->__bo_vnode->v_mount) ? WI_GIANTQ :
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WI_MPSAFEQ;
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LIST_INSERT_HEAD(&syncer_workitem_pending[queue][slot], bo,
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bo_synclist);
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mtx_unlock(&sync_mtx);
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}
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@ -1617,38 +1625,13 @@ sync_vnode(struct synclist *slp, struct bufobj **bo, struct thread *td)
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{
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struct vnode *vp;
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struct mount *mp;
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int vfslocked;
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vfslocked = 0;
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restart:
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*bo = LIST_FIRST(slp);
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if (*bo == NULL) {
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VFS_UNLOCK_GIANT(vfslocked);
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if (*bo == NULL)
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return (0);
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}
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vp = (*bo)->__bo_vnode; /* XXX */
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if (VFS_NEEDSGIANT(vp->v_mount)) {
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if (!vfslocked) {
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vfslocked = 1;
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if (mtx_trylock(&Giant) == 0) {
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mtx_unlock(&sync_mtx);
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mtx_lock(&Giant);
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mtx_lock(&sync_mtx);
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goto restart;
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}
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}
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} else {
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VFS_UNLOCK_GIANT(vfslocked);
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vfslocked = 0;
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}
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if (VOP_ISLOCKED(vp) != 0) {
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VFS_UNLOCK_GIANT(vfslocked);
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if (VOP_ISLOCKED(vp) != 0 || VI_TRYLOCK(vp) == 0)
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return (1);
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}
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if (VI_TRYLOCK(vp) == 0) {
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VFS_UNLOCK_GIANT(vfslocked);
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return (1);
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}
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/*
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* We use vhold in case the vnode does not
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* successfully sync. vhold prevents the vnode from
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@ -1660,7 +1643,6 @@ restart:
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VI_UNLOCK(vp);
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if (vn_start_write(vp, &mp, V_NOWAIT) != 0) {
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vdrop(vp);
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VFS_UNLOCK_GIANT(vfslocked);
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mtx_lock(&sync_mtx);
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return (*bo == LIST_FIRST(slp));
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}
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@ -1680,7 +1662,6 @@ restart:
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}
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BO_UNLOCK(*bo);
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vdrop(vp);
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VFS_UNLOCK_GIANT(vfslocked);
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mtx_lock(&sync_mtx);
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return (0);
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}
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@ -1691,8 +1672,8 @@ restart:
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static void
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sched_sync(void)
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{
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struct synclist *next;
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struct synclist *slp;
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struct synclist *gnext, *next;
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struct synclist *gslp, *slp;
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struct bufobj *bo;
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long starttime;
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struct thread *td = curthread;
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@ -1739,11 +1720,13 @@ sched_sync(void)
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* Skip over empty worklist slots when shutting down.
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*/
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do {
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slp = &syncer_workitem_pending[syncer_delayno];
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slp = &syncer_workitem_pending[WI_MPSAFEQ][syncer_delayno];
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gslp = &syncer_workitem_pending[WI_GIANTQ][syncer_delayno];
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syncer_delayno += 1;
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if (syncer_delayno == syncer_maxdelay)
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syncer_delayno = 0;
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next = &syncer_workitem_pending[syncer_delayno];
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next = &syncer_workitem_pending[WI_MPSAFEQ][syncer_delayno];
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gnext = &syncer_workitem_pending[WI_GIANTQ][syncer_delayno];
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/*
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* If the worklist has wrapped since the
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* it was emptied of all but syncer vnodes,
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@ -1757,7 +1740,7 @@ sched_sync(void)
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syncer_final_iter = SYNCER_SHUTDOWN_SPEEDUP;
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}
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} while (syncer_state != SYNCER_RUNNING && LIST_EMPTY(slp) &&
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syncer_worklist_len > 0);
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LIST_EMPTY(gslp) && syncer_worklist_len > 0);
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/*
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* Keep track of the last time there was anything
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@ -1777,6 +1760,21 @@ sched_sync(void)
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continue;
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}
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}
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if (!LIST_EMPTY(gslp)) {
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mtx_unlock(&sync_mtx);
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mtx_lock(&Giant);
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mtx_lock(&sync_mtx);
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while (!LIST_EMPTY(gslp)) {
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error = sync_vnode(gslp, &bo, td);
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if (error == 1) {
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LIST_REMOVE(bo, bo_synclist);
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LIST_INSERT_HEAD(gnext, bo,
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bo_synclist);
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continue;
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}
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}
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mtx_unlock(&Giant);
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}
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if (syncer_state == SYNCER_FINAL_DELAY && syncer_final_iter > 0)
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syncer_final_iter--;
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/*
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