Re: [PATCH v2 14/15] xfs: multithreaded iwalk implementation

Brian Foster
2019-07-02T17:40:34Z

On Tue, Jul 02, 2019 at 09:53:42AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> Create a parallel iwalk implementation and switch quotacheck to use it.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
> v2: conservative thread count estimates; clean out the xfs_param_t stuff
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

> fs/xfs/Makefile | 1
> fs/xfs/xfs_globals.c | 3 +
> fs/xfs/xfs_iwalk.c | 82 ++++++++++++++++++++++++++++++++++++
> fs/xfs/xfs_iwalk.h | 2 +
> fs/xfs/xfs_pwork.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++++
> fs/xfs/xfs_pwork.h | 58 +++++++++++++++++++++++++
> fs/xfs/xfs_qm.c | 2 -
> fs/xfs/xfs_sysctl.h | 3 +
> fs/xfs/xfs_sysfs.c | 40 +++++++++++++++++
> fs/xfs/xfs_trace.h | 18 ++++++++
> 10 files changed, 323 insertions(+), 1 deletion(-)
> create mode 100644 fs/xfs/xfs_pwork.c
> create mode 100644 fs/xfs/xfs_pwork.h
>
> diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
> index 6fdd481b3143..266b66613cd6 100644
> --- a/fs/xfs/Makefile
> +++ b/fs/xfs/Makefile
> @@ -92,6 +92,7 @@ xfs-y += xfs_aops.o \
> xfs_message.o \
> xfs_mount.o \
> xfs_mru_cache.o \
> + xfs_pwork.o \
> xfs_reflink.o \
> xfs_stats.o \
> xfs_super.o \
> diff --git a/fs/xfs/xfs_globals.c b/fs/xfs/xfs_globals.c
> index 4e4a7a299ccb..fa55ab8b8d80 100644
> --- a/fs/xfs/xfs_globals.c
> +++ b/fs/xfs/xfs_globals.c
> @@ -40,4 +40,7 @@ struct xfs_globals xfs_globals = {
> #else
> .bug_on_assert = false, /* assert failures WARN() */
> #endif
> +#ifdef DEBUG
> + .pwork_threads = -1, /* automatic thread detection */
> +#endif
> };
> diff --git a/fs/xfs/xfs_iwalk.c b/fs/xfs/xfs_iwalk.c
> index a0903150d2d8..d610eefed409 100644
> --- a/fs/xfs/xfs_iwalk.c
> +++ b/fs/xfs/xfs_iwalk.c
> @@ -20,6 +20,7 @@
> #include "xfs_icache.h"
> #include "xfs_health.h"
> #include "xfs_trans.h"
> +#include "xfs_pwork.h"
>
> /*
> * Walking Inodes in the Filesystem
> @@ -45,6 +46,9 @@
> */
>
> struct xfs_iwalk_ag {
> + /* parallel work control data; will be null if single threaded */
> + struct xfs_pwork pwork;
> +
> struct xfs_mount *mp;
> struct xfs_trans *tp;
>
> @@ -182,6 +186,9 @@ xfs_iwalk_ag_recs(
>
> trace_xfs_iwalk_ag_rec(mp, agno, irec);
>
> + if (xfs_pwork_want_abort(&iwag->pwork))
> + return 0;
> +
> if (iwag->inobt_walk_fn) {
> error = iwag->inobt_walk_fn(mp, tp, agno, irec,
> iwag->data);
> @@ -193,6 +200,9 @@ xfs_iwalk_ag_recs(
> continue;
>
> for (j = 0; j < XFS_INODES_PER_CHUNK; j++) {
> + if (xfs_pwork_want_abort(&iwag->pwork))
> + return 0;
> +
> /* Skip if this inode is free */
> if (XFS_INOBT_MASK(j) & irec->ir_free)
> continue;
> @@ -387,6 +397,8 @@ xfs_iwalk_ag(
> struct xfs_inobt_rec_incore *irec;
>
> cond_resched();
> + if (xfs_pwork_want_abort(&iwag->pwork))
> + goto out;
>
> /* Fetch the inobt record. */
> irec = &iwag->recs[iwag->nr_recs];
> @@ -520,6 +532,7 @@ xfs_iwalk(
> .sz_recs = xfs_iwalk_prefetch(inode_records),
> .trim_start = 1,
> .skip_empty = 1,
> + .pwork = XFS_PWORK_SINGLE_THREADED,
> };
> xfs_agnumber_t agno = XFS_INO_TO_AGNO(mp, startino);
> int error;
> @@ -541,6 +554,74 @@ xfs_iwalk(
> return error;
> }
>
> +/* Run per-thread iwalk work. */
> +static int
> +xfs_iwalk_ag_work(
> + struct xfs_mount *mp,
> + struct xfs_pwork *pwork)
> +{
> + struct xfs_iwalk_ag *iwag;
> + int error = 0;
> +
> + iwag = container_of(pwork, struct xfs_iwalk_ag, pwork);
> + if (xfs_pwork_want_abort(pwork))
> + goto out;
> +
> + error = xfs_iwalk_alloc(iwag);
> + if (error)
> + goto out;
> +
> + error = xfs_iwalk_ag(iwag);
> + xfs_iwalk_free(iwag);
> +out:
> + kmem_free(iwag);
> + return error;
> +}
> +
> +/*
> + * Walk all the inodes in the filesystem using multiple threads to process each
> + * AG.
> + */
> +int
> +xfs_iwalk_threaded(
> + struct xfs_mount *mp,
> + xfs_ino_t startino,
> + xfs_iwalk_fn iwalk_fn,
> + unsigned int inode_records,
> + void *data)
> +{
> + struct xfs_pwork_ctl pctl;
> + xfs_agnumber_t agno = XFS_INO_TO_AGNO(mp, startino);
> + unsigned int nr_threads;
> + int error;
> +
> + ASSERT(agno < mp->m_sb.sb_agcount);
> +
> + nr_threads = xfs_pwork_guess_datadev_parallelism(mp);
> + error = xfs_pwork_init(mp, &pctl, xfs_iwalk_ag_work, "xfs_iwalk",
> + nr_threads);
> + if (error)
> + return error;
> +
> + for (; agno < mp->m_sb.sb_agcount; agno++) {
> + struct xfs_iwalk_ag *iwag;
> +
> + if (xfs_pwork_ctl_want_abort(&pctl))
> + break;
> +
> + iwag = kmem_zalloc(sizeof(struct xfs_iwalk_ag), KM_SLEEP);
> + iwag->mp = mp;
> + iwag->iwalk_fn = iwalk_fn;
> + iwag->data = data;
> + iwag->startino = startino;
> + iwag->sz_recs = xfs_iwalk_prefetch(inode_records);
> + xfs_pwork_queue(&pctl, &iwag->pwork);
> + startino = XFS_AGINO_TO_INO(mp, agno + 1, 0);
> + }
> +
> + return xfs_pwork_destroy(&pctl);
> +}
> +
> /*
> * Allow callers to cache up to a page's worth of inobt records. This reflects
> * the existing inumbers prefetching behavior. Since the inobt walk does not
> @@ -601,6 +682,7 @@ xfs_inobt_walk(
> .data = data,
> .startino = startino,
> .sz_recs = xfs_inobt_walk_prefetch(inobt_records),
> + .pwork = XFS_PWORK_SINGLE_THREADED,
> };
> xfs_agnumber_t agno = XFS_INO_TO_AGNO(mp, startino);
> int error;
> diff --git a/fs/xfs/xfs_iwalk.h b/fs/xfs/xfs_iwalk.h
> index 94fad060b3e9..22c31763a9b8 100644
> --- a/fs/xfs/xfs_iwalk.h
> +++ b/fs/xfs/xfs_iwalk.h
> @@ -15,6 +15,8 @@ typedef int (*xfs_iwalk_fn)(struct xfs_mount *mp, struct xfs_trans *tp,
>
> int xfs_iwalk(struct xfs_mount *mp, struct xfs_trans *tp, xfs_ino_t startino,
> xfs_iwalk_fn iwalk_fn, unsigned int inode_records, void *data);
> +int xfs_iwalk_threaded(struct xfs_mount *mp, xfs_ino_t startino,
> + xfs_iwalk_fn iwalk_fn, unsigned int inode_records, void *data);
>
> /* Walk all inode btree records in the filesystem starting from @startino. */
> typedef int (*xfs_inobt_walk_fn)(struct xfs_mount *mp, struct xfs_trans *tp,
> diff --git a/fs/xfs/xfs_pwork.c b/fs/xfs/xfs_pwork.c
> new file mode 100644
> index 000000000000..fee727d07822
> --- /dev/null
> +++ b/fs/xfs/xfs_pwork.c
> @@ -0,0 +1,115 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2019 Oracle. All Rights Reserved.
> + * Author: Darrick J. Wong <darrick.wong@oracle.com>
> + */
> +#include "xfs.h"
> +#include "xfs_fs.h"
> +#include "xfs_shared.h"
> +#include "xfs_format.h"
> +#include "xfs_log_format.h"
> +#include "xfs_trans_resv.h"
> +#include "xfs_mount.h"
> +#include "xfs_trace.h"
> +#include "xfs_sysctl.h"
> +#include "xfs_pwork.h"
> +
> +/*
> + * Parallel Work Queue
> + * ===================
> + *
> + * Abstract away the details of running a large and "obviously" parallelizable
> + * task across multiple CPUs. Callers initialize the pwork control object with
> + * a desired level of parallelization and a work function. Next, they embed
> + * struct xfs_pwork in whatever structure they use to pass work context to a
> + * worker thread and queue that pwork. The work function will be passed the
> + * pwork item when it is run (from process context) and any returned error will
> + * be recorded in xfs_pwork_ctl.error. Work functions should check for errors
> + * and abort if necessary; the non-zeroness of xfs_pwork_ctl.error does not
> + * stop workqueue item processing.
> + *
> + * This is the rough equivalent of the xfsprogs workqueue code, though we can't
> + * reuse that name here.
> + */
> +
> +/* Invoke our caller's function. */
> +static void
> +xfs_pwork_work(
> + struct work_struct *work)
> +{
> + struct xfs_pwork *pwork;
> + struct xfs_pwork_ctl *pctl;
> + int error;
> +
> + pwork = container_of(work, struct xfs_pwork, work);
> + pctl = pwork->pctl;
> + error = pctl->work_fn(pctl->mp, pwork);
> + if (error && !pctl->error)
> + pctl->error = error;
> +}
> +
> +/*
> + * Set up control data for parallel work. @work_fn is the function that will
> + * be called. @tag will be written into the kernel threads. @nr_threads is
> + * the level of parallelism desired, or 0 for no limit.
> + */
> +int
> +xfs_pwork_init(
> + struct xfs_mount *mp,
> + struct xfs_pwork_ctl *pctl,
> + xfs_pwork_work_fn work_fn,
> + const char *tag,
> + unsigned int nr_threads)
> +{
> +#ifdef DEBUG
> + if (xfs_globals.pwork_threads >= 0)
> + nr_threads = xfs_globals.pwork_threads;
> +#endif
> + trace_xfs_pwork_init(mp, nr_threads, current->pid);
> +
> + pctl->wq = alloc_workqueue("%s-%d", WQ_FREEZABLE, nr_threads, tag,
> + current->pid);
> + if (!pctl->wq)
> + return -ENOMEM;
> + pctl->work_fn = work_fn;
> + pctl->error = 0;
> + pctl->mp = mp;
> +
> + return 0;
> +}
> +
> +/* Queue some parallel work. */
> +void
> +xfs_pwork_queue(
> + struct xfs_pwork_ctl *pctl,
> + struct xfs_pwork *pwork)
> +{
> + INIT_WORK(&pwork->work, xfs_pwork_work);
> + pwork->pctl = pctl;
> + queue_work(pctl->wq, &pwork->work);
> +}
> +
> +/* Wait for the work to finish and tear down the control structure. */
> +int
> +xfs_pwork_destroy(
> + struct xfs_pwork_ctl *pctl)
> +{
> + destroy_workqueue(pctl->wq);
> + pctl->wq = NULL;
> + return pctl->error;
> +}
> +
> +/*
> + * Return the amount of parallelism that the data device can handle, or 0 for
> + * no limit.
> + */
> +unsigned int
> +xfs_pwork_guess_datadev_parallelism(
> + struct xfs_mount *mp)
> +{
> + /*
> + * For now we'll go with the most conservative setting possible,
> + * which is two threads for an SSD and 1 thread everywhere else.
> + */
> + return blk_queue_nonrot(btp->bt_bdev->bd_queue) ? 2 : 1;
> +}
> diff --git a/fs/xfs/xfs_pwork.h b/fs/xfs/xfs_pwork.h
> new file mode 100644
> index 000000000000..99a9d210d49e
> --- /dev/null
> +++ b/fs/xfs/xfs_pwork.h
> @@ -0,0 +1,58 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2019 Oracle. All Rights Reserved.
> + * Author: Darrick J. Wong <darrick.wong@oracle.com>
> + */
> +#ifndef __XFS_PWORK_H__
> +#define __XFS_PWORK_H__
> +
> +struct xfs_pwork;
> +struct xfs_mount;
> +
> +typedef int (*xfs_pwork_work_fn)(struct xfs_mount *mp, struct xfs_pwork *pwork);
> +
> +/*
> + * Parallel work coordination structure.
> + */
> +struct xfs_pwork_ctl {
> + struct workqueue_struct *wq;
> + struct xfs_mount *mp;
> + xfs_pwork_work_fn work_fn;
> + int error;
> +};
> +
> +/*
> + * Embed this parallel work control item inside your own work structure,
> + * then queue work with it.
> + */
> +struct xfs_pwork {
> + struct work_struct work;
> + struct xfs_pwork_ctl *pctl;
> +};
> +
> +#define XFS_PWORK_SINGLE_THREADED { .pctl = NULL }
> +
> +/* Have we been told to abort? */
> +static inline bool
> +xfs_pwork_ctl_want_abort(
> + struct xfs_pwork_ctl *pctl)
> +{
> + return pctl && pctl->error;
> +}
> +
> +/* Have we been told to abort? */
> +static inline bool
> +xfs_pwork_want_abort(
> + struct xfs_pwork *pwork)
> +{
> + return xfs_pwork_ctl_want_abort(pwork->pctl);
> +}
> +
> +int xfs_pwork_init(struct xfs_mount *mp, struct xfs_pwork_ctl *pctl,
> + xfs_pwork_work_fn work_fn, const char *tag,
> + unsigned int nr_threads);
> +void xfs_pwork_queue(struct xfs_pwork_ctl *pctl, struct xfs_pwork *pwork);
> +int xfs_pwork_destroy(struct xfs_pwork_ctl *pctl);
> +unsigned int xfs_pwork_guess_datadev_parallelism(struct xfs_mount *mp);
> +
> +#endif /* __XFS_PWORK_H__ */
> diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
> index 588e36fe43f2..fb7a41fdde7f 100644
> --- a/fs/xfs/xfs_qm.c
> +++ b/fs/xfs/xfs_qm.c
> @@ -1300,7 +1300,7 @@ xfs_qm_quotacheck(
> flags |= XFS_PQUOTA_CHKD;
> }
>
> - error = xfs_iwalk(mp, NULL, 0, xfs_qm_dqusage_adjust, 0, NULL);
> + error = xfs_iwalk_threaded(mp, 0, xfs_qm_dqusage_adjust, 0, NULL);
> if (error)
> goto error_return;
>
> diff --git a/fs/xfs/xfs_sysctl.h b/fs/xfs/xfs_sysctl.h
> index ad7f9be13087..8abf4640f1d5 100644
> --- a/fs/xfs/xfs_sysctl.h
> +++ b/fs/xfs/xfs_sysctl.h
> @@ -82,6 +82,9 @@ enum {
> extern xfs_param_t xfs_params;
>
> struct xfs_globals {
> +#ifdef DEBUG
> + int pwork_threads; /* parallel workqueue threads */
> +#endif
> int log_recovery_delay; /* log recovery delay (secs) */
> int mount_delay; /* mount setup delay (secs) */
> bool bug_on_assert; /* BUG() the kernel on assert failure */
> diff --git a/fs/xfs/xfs_sysfs.c b/fs/xfs/xfs_sysfs.c
> index 688366d42cd8..ddd0bf7a4740 100644
> --- a/fs/xfs/xfs_sysfs.c
> +++ b/fs/xfs/xfs_sysfs.c
> @@ -204,11 +204,51 @@ always_cow_show(
> }
> XFS_SYSFS_ATTR_RW(always_cow);
>
> +#ifdef DEBUG
> +/*
> + * Override how many threads the parallel work queue is allowed to create.
> + * This has to be a debug-only global (instead of an errortag) because one of
> + * the main users of parallel workqueues is mount time quotacheck.
> + */
> +STATIC ssize_t
> +pwork_threads_store(
> + struct kobject *kobject,
> + const char *buf,
> + size_t count)
> +{
> + int ret;
> + int val;
> +
> + ret = kstrtoint(buf, 0, &val);
> + if (ret)
> + return ret;
> +
> + if (val < -1 || val > num_possible_cpus())
> + return -EINVAL;
> +
> + xfs_globals.pwork_threads = val;
> +
> + return count;
> +}
> +
> +STATIC ssize_t
> +pwork_threads_show(
> + struct kobject *kobject,
> + char *buf)
> +{
> + return snprintf(buf, PAGE_SIZE, "%d\n", xfs_globals.pwork_threads);
> +}
> +XFS_SYSFS_ATTR_RW(pwork_threads);
> +#endif /* DEBUG */
> +
> static struct attribute *xfs_dbg_attrs[] = {
> ATTR_LIST(bug_on_assert),
> ATTR_LIST(log_recovery_delay),
> ATTR_LIST(mount_delay),
> ATTR_LIST(always_cow),
> +#ifdef DEBUG
> + ATTR_LIST(pwork_threads),
> +#endif
> NULL,
> };
>
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index e61d519961a1..8094b1920eef 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -3557,6 +3557,24 @@ TRACE_EVENT(xfs_iwalk_ag_rec,
> __entry->startino, __entry->freemask)
> )
>
> +TRACE_EVENT(xfs_pwork_init,
> + TP_PROTO(struct xfs_mount *mp, unsigned int nr_threads, pid_t pid),
> + TP_ARGS(mp, nr_threads, pid),
> + TP_STRUCT__entry(
> + __field(dev_t, dev)
> + __field(unsigned int, nr_threads)
> + __field(pid_t, pid)
> + ),
> + TP_fast_assign(
> + __entry->dev = mp->m_super->s_dev;
> + __entry->nr_threads = nr_threads;
> + __entry->pid = pid;
> + ),
> + TP_printk("dev %d:%d nr_threads %u pid %u",
> + MAJOR(__entry->dev), MINOR(__entry->dev),
> + __entry->nr_threads, __entry->pid)
> +)
> +
> #endif /* _TRACE_XFS_H */
>
> #undef TRACE_INCLUDE_PATH