Date: Wed, 22 Mar 2023 23:57:28 GMT From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: b5d43972e394 - main - vfs: decouple freevnodes from vnode batching Message-ID: <202303222357.32MNvSbm048634@gitrepo.freebsd.org>
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The branch main has been updated by mjg: URL: https://cgit.FreeBSD.org/src/commit/?id=b5d43972e3941d6c03d935dc423385f3c2178d68 commit b5d43972e3941d6c03d935dc423385f3c2178d68 Author: Mateusz Guzik <mjg@FreeBSD.org> AuthorDate: 2023-03-21 07:27:25 +0000 Commit: Mateusz Guzik <mjg@FreeBSD.org> CommitDate: 2023-03-22 23:57:25 +0000 vfs: decouple freevnodes from vnode batching In principle one cpu can keep vholding vnodes, while another vdrops them. In this case it may be the local count will keep growing in an unbounded manner. Roll it up after a threshold instead. While here move it out of dpcpu into struct pcpu. Reviewed by: kib (previous version) Differential Revision: https://reviews.freebsd.org/D39195 --- sys/kern/vfs_subr.c | 55 ++++++++++++++++++++++++++++++++--------------------- sys/sys/pcpu.h | 3 ++- 2 files changed, 35 insertions(+), 23 deletions(-) diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c index c117ada017c9..d89e0ed13dd5 100644 --- a/sys/kern/vfs_subr.c +++ b/sys/kern/vfs_subr.c @@ -287,7 +287,6 @@ SYSCTL_INT(_debug, OID_AUTO, rush_requests, CTLFLAG_RW, &stat_rush_requests, 0, #define VDBATCH_SIZE 8 struct vdbatch { u_int index; - long freevnodes; struct mtx lock; struct vnode *tab[VDBATCH_SIZE]; }; @@ -1418,48 +1417,62 @@ static int vnlruproc_sig; * at any given moment can still exceed slop, but it should not be by significant * margin in practice. */ -#define VNLRU_FREEVNODES_SLOP 128 +#define VNLRU_FREEVNODES_SLOP 126 + +static void __noinline +vfs_freevnodes_rollup(int8_t *lfreevnodes) +{ + + atomic_add_long(&freevnodes, *lfreevnodes); + *lfreevnodes = 0; + critical_exit(); +} static __inline void vfs_freevnodes_inc(void) { - struct vdbatch *vd; + int8_t *lfreevnodes; critical_enter(); - vd = DPCPU_PTR(vd); - vd->freevnodes++; - critical_exit(); + lfreevnodes = PCPU_PTR(vfs_freevnodes); + (*lfreevnodes)++; + if (__predict_false(*lfreevnodes == VNLRU_FREEVNODES_SLOP)) + vfs_freevnodes_rollup(lfreevnodes); + else + critical_exit(); } static __inline void vfs_freevnodes_dec(void) { - struct vdbatch *vd; + int8_t *lfreevnodes; critical_enter(); - vd = DPCPU_PTR(vd); - vd->freevnodes--; - critical_exit(); + lfreevnodes = PCPU_PTR(vfs_freevnodes); + (*lfreevnodes)--; + if (__predict_false(*lfreevnodes == -VNLRU_FREEVNODES_SLOP)) + vfs_freevnodes_rollup(lfreevnodes); + else + critical_exit(); } static u_long vnlru_read_freevnodes(void) { - struct vdbatch *vd; - long slop; + long slop, rfreevnodes; int cpu; - mtx_assert(&vnode_list_mtx, MA_OWNED); - if (freevnodes > freevnodes_old) - slop = freevnodes - freevnodes_old; + rfreevnodes = atomic_load_long(&freevnodes); + + if (rfreevnodes > freevnodes_old) + slop = rfreevnodes - freevnodes_old; else - slop = freevnodes_old - freevnodes; + slop = freevnodes_old - rfreevnodes; if (slop < VNLRU_FREEVNODES_SLOP) - return (freevnodes >= 0 ? freevnodes : 0); - freevnodes_old = freevnodes; + return (rfreevnodes >= 0 ? rfreevnodes : 0); + freevnodes_old = rfreevnodes; CPU_FOREACH(cpu) { - vd = DPCPU_ID_PTR((cpu), vd); - freevnodes_old += vd->freevnodes; + freevnodes_old += cpuid_to_pcpu[cpu]->pc_vfs_freevnodes; } return (freevnodes_old >= 0 ? freevnodes_old : 0); } @@ -3513,7 +3526,6 @@ vdbatch_process(struct vdbatch *vd) mtx_lock(&vnode_list_mtx); critical_enter(); - freevnodes += vd->freevnodes; for (i = 0; i < VDBATCH_SIZE; i++) { vp = vd->tab[i]; TAILQ_REMOVE(&vnode_list, vp, v_vnodelist); @@ -3522,7 +3534,6 @@ vdbatch_process(struct vdbatch *vd) vp->v_dbatchcpu = NOCPU; } mtx_unlock(&vnode_list_mtx); - vd->freevnodes = 0; bzero(vd->tab, sizeof(vd->tab)); vd->index = 0; critical_exit(); diff --git a/sys/sys/pcpu.h b/sys/sys/pcpu.h index 14bef5cf690e..9ac4144d3267 100644 --- a/sys/sys/pcpu.h +++ b/sys/sys/pcpu.h @@ -189,7 +189,8 @@ struct pcpu { long pc_cp_time[CPUSTATES]; /* statclock ticks */ struct _device *pc_device; /* CPU device handle */ void *pc_netisr; /* netisr SWI cookie */ - int pc_unused1; /* unused field */ + int8_t pc_vfs_freevnodes; /* freevnodes counter */ + char pc_unused1[3]; /* unused pad */ int pc_domain; /* Memory domain. */ struct rm_queue pc_rm_queue; /* rmlock list of trackers */ uintptr_t pc_dynamic; /* Dynamic per-cpu data area */
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