Date: Sun, 29 Nov 2015 21:42:26 +0000 (UTC) From: Kirk McKusick <mckusick@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r291460 - head/sys/kern Message-ID: <201511292142.tATLgQW0042923@repo.freebsd.org>
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Author: mckusick Date: Sun Nov 29 21:42:26 2015 New Revision: 291460 URL: https://svnweb.freebsd.org/changeset/base/291460 Log: As the kernel allocates and frees vnodes, it fully initializes them on every allocation and fully releases them on every free. These are not trivial costs: it starts by zeroing a large structure then initializes a mutex, a lock manager lock, an rw lock, four lists, and six pointers. And looking at vfs.vnodes_created, these operations are being done millions of times an hour on a busy machine. As a performance optimization, this code update uses the uma_init and uma_fini routines to do these initializations and cleanups only as the vnodes enter and leave the vnode_zone. With this change the initializations are only done kern.maxvnodes times at system startup and then only rarely again. The frees are done only if the vnode_zone shrinks which never happens in practice. For those curious about the avoided work, look at the vnode_init() and vnode_fini() functions in kern/vfs_subr.c to see the code that has been removed from the main vnode allocation/free path. Reviewed by: kib Tested by: Peter Holm Modified: head/sys/kern/vfs_subr.c Modified: head/sys/kern/vfs_subr.c ============================================================================== --- head/sys/kern/vfs_subr.c Sun Nov 29 21:01:02 2015 (r291459) +++ head/sys/kern/vfs_subr.c Sun Nov 29 21:42:26 2015 (r291460) @@ -346,6 +346,66 @@ PCTRIE_DEFINE(BUF, buf, b_lblkno, buf_tr #ifndef MAXVNODES_MAX #define MAXVNODES_MAX (512 * 1024 * 1024 / 64) /* 8M */ #endif + +/* + * Initialize a vnode as it first enters the zone. + */ +static int +vnode_init(void *mem, int size, int flags) +{ + struct vnode *vp; + struct bufobj *bo; + + vp = mem; + bzero(vp, size); + /* + * Setup locks. + */ + vp->v_vnlock = &vp->v_lock; + mtx_init(&vp->v_interlock, "vnode interlock", NULL, MTX_DEF); + /* + * By default, don't allow shared locks unless filesystems opt-in. + */ + lockinit(vp->v_vnlock, PVFS, "vnode", VLKTIMEOUT, + LK_NOSHARE | LK_IS_VNODE); + /* + * Initialize bufobj. + */ + bo = &vp->v_bufobj; + bo->__bo_vnode = vp; + rw_init(BO_LOCKPTR(bo), "bufobj interlock"); + bo->bo_private = vp; + TAILQ_INIT(&bo->bo_clean.bv_hd); + TAILQ_INIT(&bo->bo_dirty.bv_hd); + /* + * Initialize namecache. + */ + LIST_INIT(&vp->v_cache_src); + TAILQ_INIT(&vp->v_cache_dst); + /* + * Initialize rangelocks. + */ + rangelock_init(&vp->v_rl); + return (0); +} + +/* + * Free a vnode when it is cleared from the zone. + */ +static void +vnode_fini(void *mem, int size) +{ + struct vnode *vp; + struct bufobj *bo; + + vp = mem; + rangelock_destroy(&vp->v_rl); + lockdestroy(vp->v_vnlock); + mtx_destroy(&vp->v_interlock); + bo = &vp->v_bufobj; + rw_destroy(BO_LOCKPTR(bo)); +} + static void vntblinit(void *dummy __unused) { @@ -379,7 +439,7 @@ vntblinit(void *dummy __unused) TAILQ_INIT(&vnode_free_list); mtx_init(&vnode_free_list_mtx, "vnode_free_list", NULL, MTX_DEF); vnode_zone = uma_zcreate("VNODE", sizeof (struct vnode), NULL, NULL, - NULL, NULL, UMA_ALIGN_PTR, 0); + vnode_init, vnode_fini, UMA_ALIGN_PTR, 0); vnodepoll_zone = uma_zcreate("VNODEPOLL", sizeof (struct vpollinfo), NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); /* @@ -1223,8 +1283,8 @@ getnewvnode(const char *tag, struct moun struct vnode **vpp) { struct vnode *vp; - struct bufobj *bo; struct thread *td; + struct lock_object *lo; static int cyclecount; int error; @@ -1271,40 +1331,42 @@ getnewvnode(const char *tag, struct moun mtx_unlock(&vnode_free_list_mtx); alloc: atomic_add_long(&vnodes_created, 1); - vp = (struct vnode *) uma_zalloc(vnode_zone, M_WAITOK|M_ZERO); + vp = (struct vnode *) uma_zalloc(vnode_zone, M_WAITOK); /* - * Setup locks. - */ - vp->v_vnlock = &vp->v_lock; - mtx_init(&vp->v_interlock, "vnode interlock", NULL, MTX_DEF); - /* - * By default, don't allow shared locks unless filesystems - * opt-in. - */ - lockinit(vp->v_vnlock, PVFS, tag, VLKTIMEOUT, LK_NOSHARE | LK_IS_VNODE); - /* - * Initialize bufobj. + * Locks are given the generic name "vnode" when created. + * Follow the historic practice of using the filesystem + * name when they allocated, e.g., "zfs", "ufs", "nfs, etc. + * + * Locks live in a witness group keyed on their name. Thus, + * when a lock is renamed, it must also move from the witness + * group of its old name to the witness group of its new name. + * + * The change only needs to be made when the vnode moves + * from one filesystem type to another. We ensure that each + * filesystem use a single static name pointer for its tag so + * that we can compare pointers rather than doing a strcmp(). */ - bo = &vp->v_bufobj; - bo->__bo_vnode = vp; - rw_init(BO_LOCKPTR(bo), "bufobj interlock"); - bo->bo_ops = &buf_ops_bio; - bo->bo_private = vp; - TAILQ_INIT(&bo->bo_clean.bv_hd); - TAILQ_INIT(&bo->bo_dirty.bv_hd); + lo = &vp->v_vnlock->lock_object; + if (lo->lo_name != tag) { + lo->lo_name = tag; + WITNESS_DESTROY(lo); + WITNESS_INIT(lo, tag); + } /* - * Initialize namecache. + * By default, don't allow shared locks unless filesystems opt-in. */ - LIST_INIT(&vp->v_cache_src); - TAILQ_INIT(&vp->v_cache_dst); + vp->v_vnlock->lock_object.lo_flags |= LK_NOSHARE; /* * Finalize various vnode identity bits. */ + KASSERT(vp->v_object == NULL, ("stale v_object %p", vp)); + KASSERT(vp->v_lockf == NULL, ("stale v_lockf %p", vp)); + KASSERT(vp->v_pollinfo == NULL, ("stale v_pollinfo %p", vp)); vp->v_type = VNON; vp->v_tag = tag; vp->v_op = vops; v_init_counters(vp); - vp->v_data = NULL; + vp->v_bufobj.bo_ops = &buf_ops_bio; #ifdef MAC mac_vnode_init(vp); if (mp != NULL && (mp->mnt_flag & MNT_MULTILABEL) == 0) @@ -1313,11 +1375,10 @@ alloc: printf("NULL mp in getnewvnode()\n"); #endif if (mp != NULL) { - bo->bo_bsize = mp->mnt_stat.f_iosize; + vp->v_bufobj.bo_bsize = mp->mnt_stat.f_iosize; if ((mp->mnt_kern_flag & MNTK_NOKNOTE) != 0) vp->v_vflag |= VV_NOKNOTE; } - rangelock_init(&vp->v_rl); /* * For the filesystems which do not use vfs_hash_insert(), @@ -2683,6 +2744,12 @@ _vdrop(struct vnode *vp, bool locked) } /* * The vnode has been marked for destruction, so free it. + * + * The vnode will be returned to the zone where it will + * normally remain until it is needed for another vnode. We + * need to cleanup (or verify that the cleanup has already + * been done) any residual data left from its current use + * so as not to contaminate the freshly allocated vnode. */ CTR2(KTR_VFS, "%s: destroying the vnode %p", __func__, vp); atomic_subtract_long(&numvnodes, 1); @@ -2707,16 +2774,17 @@ _vdrop(struct vnode *vp, bool locked) #ifdef MAC mac_vnode_destroy(vp); #endif - if (vp->v_pollinfo != NULL) + if (vp->v_pollinfo != NULL) { destroy_vpollinfo(vp->v_pollinfo); + vp->v_pollinfo = NULL; + } #ifdef INVARIANTS /* XXX Elsewhere we detect an already freed vnode via NULL v_op. */ vp->v_op = NULL; #endif - rangelock_destroy(&vp->v_rl); - lockdestroy(vp->v_vnlock); - mtx_destroy(&vp->v_interlock); - rw_destroy(BO_LOCKPTR(bo)); + vp->v_iflag = 0; + vp->v_vflag = 0; + bo->bo_flag = 0; uma_zfree(vnode_zone, vp); } @@ -3081,6 +3149,7 @@ vgonel(struct vnode *vp) * Clear the advisory locks and wake up waiting threads. */ (void)VOP_ADVLOCKPURGE(vp); + vp->v_lockf = NULL; /* * Delete from old mount point vnode list. */
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