On Tue, 21 Jan 2014 14:59:43 +0100, Andreas Rohner wrote:
> With this ioctl the segment usage information in the SUFILE can be
> updated from userspace.
>
> This is useful, because it allows the GC to modify and update segment
> usage entries for specific segments, which enables it to avoid
> unnecessary write operations.
>
> If a segment needs to be cleaned, but there is no or very little free
> space to be gained, the cleaning operation basically degrades to
> needless expensive copying of data. In the end the only thing that
> changes is the location of the data and a timestamp in the segment
> usage info. With this ioctl the GC can skip the copying and update the
> segment usage entries directly instead.
>
> Additionally this patch implements a simple check in
> nilfs_reclaim_segment. If the number of free blocks that can be gained
> by cleaning the segments is below the threshold of minblocks, it simply
> updates the segment usage information instead.
>
> Signed-off-by: Andreas Rohner <andreas.rohner@xxxxxxx>
> ---
> include/nilfs.h | 2 ++
> include/nilfs2_fs.h | 41 +++++++++++++++++++++++++++++++++++++++++
> lib/gc.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
> lib/nilfs.c | 26 ++++++++++++++++++++++++++
> 4 files changed, 112 insertions(+), 1 deletion(-)
>
> diff --git a/include/nilfs.h b/include/nilfs.h
> index 56286a9..1e9b034 100644
> --- a/include/nilfs.h
> +++ b/include/nilfs.h
> @@ -299,6 +299,8 @@ int nilfs_delete_checkpoint(struct nilfs *, nilfs_cno_t);
> int nilfs_get_cpstat(const struct nilfs *, struct nilfs_cpstat *);
> ssize_t nilfs_get_suinfo(const struct nilfs *, __u64, struct nilfs_suinfo *,
> size_t);
> +ssize_t nilfs_set_suinfo(const struct nilfs *, struct nilfs_suinfo_update *,
> + size_t);
> int nilfs_get_sustat(const struct nilfs *, struct nilfs_sustat *);
> ssize_t nilfs_get_vinfo(const struct nilfs *, struct nilfs_vinfo *, size_t);
> ssize_t nilfs_get_bdescs(const struct nilfs *, struct nilfs_bdesc *, size_t);
> diff --git a/include/nilfs2_fs.h b/include/nilfs2_fs.h
> index e674f44..181c482 100644
> --- a/include/nilfs2_fs.h
> +++ b/include/nilfs2_fs.h
> @@ -713,6 +713,45 @@ static inline int nilfs_suinfo_clean(const struct nilfs_suinfo *si)
> return !si->sui_flags;
> }
>
> +/**
> + * nilfs_suinfo_update - segment usage information update
> + * @sup_segnum: segment number
> + * @sup_flags: flags for which fields are active in sup_sui
> + * @sup_sui: segment usage information
> + */
> +struct nilfs_suinfo_update {
> + __u64 sup_segnum;
> + __u32 sup_flags;
> + struct nilfs_suinfo sup_sui;
> +};
> +
> +enum {
> + NILFS_SUINFO_UPDATE_LASTMOD,
> + NILFS_SUINFO_UPDATE_NBLOCKS,
> + NILFS_SUINFO_UPDATE_FLAGS,
> +};
> +
> +#define NILFS_SUINFO_UPDATE_FNS(flag, name) \
> +static inline void \
> +nilfs_suinfo_update_set_##name(struct nilfs_suinfo_update *sup) \
> +{ \
> + sup->sup_flags |= 1UL << NILFS_SUINFO_UPDATE_##flag; \
> +} \
> +static inline void \
> +nilfs_suinfo_update_clear_##name(struct nilfs_suinfo_update *sup) \
> +{ \
> + sup->sup_flags &= ~(1UL << NILFS_SUINFO_UPDATE_##flag); \
> +} \
> +static inline int \
> +nilfs_suinfo_update_##name(const struct nilfs_suinfo_update *sup) \
> +{ \
> + return !!(sup->sup_flags & (1UL << NILFS_SUINFO_UPDATE_##flag));\
> +}
> +
> +NILFS_SUINFO_UPDATE_FNS(LASTMOD, lastmod)
> +NILFS_SUINFO_UPDATE_FNS(NBLOCKS, nblocks)
> +NILFS_SUINFO_UPDATE_FNS(FLAGS, flags)
> +
> /* ioctl */
> enum {
> NILFS_CHECKPOINT,
> @@ -867,5 +906,7 @@ struct nilfs_bdesc {
> _IOW(NILFS_IOCTL_IDENT, 0x8B, __u64)
> #define NILFS_IOCTL_SET_ALLOC_RANGE \
> _IOW(NILFS_IOCTL_IDENT, 0x8C, __u64[2])
> +#define NILFS_IOCTL_SET_SUINFO \
> + _IOW(NILFS_IOCTL_IDENT, 0x8D, struct nilfs_argv)
>
> #endif /* _LINUX_NILFS_FS_H */
> diff --git a/lib/gc.c b/lib/gc.c
> index 0b0e2d6..ebbe0ca 100644
> --- a/lib/gc.c
> +++ b/lib/gc.c
> @@ -29,6 +29,10 @@
> #include <syslog.h>
> #endif /* HAVE_SYSLOG_H */
>
> +#if HAVE_SYS_TIME_H
> +#include <sys/time.h>
> +#endif /* HAVE_SYS_TIME */
> +
> #include <errno.h>
> #include <assert.h>
> #include <stdarg.h>
> @@ -615,7 +619,10 @@ ssize_t nilfs_reclaim_segment(struct nilfs *nilfs,
> {
> struct nilfs_vector *vdescv, *bdescv, *periodv, *vblocknrv;
> sigset_t sigset, oldset, waitset;
> - ssize_t n, ret = -1;
> + ssize_t n, i, ret = -1;
> + __u32 freeblocks;
> + struct nilfs_suinfo_update *supv;
> + struct timeval tv;
>
> if (nsegs == 0)
> return 0;
> @@ -678,6 +685,41 @@ ssize_t nilfs_reclaim_segment(struct nilfs *nilfs,
> goto out_lock;
> }
>
> + freeblocks = (nilfs_get_blocks_per_segment(nilfs) * n)
> + - (nilfs_vector_get_size(vdescv)
> + + nilfs_vector_get_size(bdescv));
> +
> + /* if there are less free blocks than the
> + * minimal threshold try to update suinfo
> + * instead of cleaning */
> + if (freeblocks < minblocks * n) {
> + ret = gettimeofday(&tv, NULL);
> + if (ret < 0)
> + goto out_lock;
> +
> + supv = malloc(sizeof(struct nilfs_suinfo_update) * n);
> + if (supv == NULL) {
> + ret = -1;
> + goto out_lock;
> + }
> +
> + for (i = 0; i < n; ++i) {
> + supv[i].sup_segnum = segnums[i];
> + supv[i].sup_flags = 0;
> + nilfs_suinfo_update_set_lastmod(&supv[i]);
> + supv[i].sup_sui.sui_lastmod = tv.tv_sec;
> + }
> +
> + ret = nilfs_set_suinfo(nilfs, supv, n);
> + free(supv);
> + if (ret >= 0) {
> + /* success, tell caller
> + * to try another segment/s */
> + ret = -EGCTRYAGAIN;
> + goto out_lock;
> + }
You should design the new reclaim function so that it turns off the
logic using nilfs_set_suinfo() once nilfs_set_suinfo() returned a
status code < 0 and errno was ENOTTY.
This fallback logic is needed to keep compatibility for old kernel.
In addition, whether applying the optimization or not, should be
selectable in /etc/nilfs_cleanerd.conf.
> + }
> +
> ret = nilfs_clean_segments(nilfs,
> nilfs_vector_get_data(vdescv),
> nilfs_vector_get_size(vdescv),
> diff --git a/lib/nilfs.c b/lib/nilfs.c
> index 7265830..dbd03e6 100644
> --- a/lib/nilfs.c
> +++ b/lib/nilfs.c
> @@ -548,6 +548,32 @@ ssize_t nilfs_get_suinfo(const struct nilfs *nilfs, __u64 segnum,
> }
>
> /**
> + * nilfs_set_suinfo -
> + * @nilfs:
Please fill the summary line of this function.
I'll continue reviewing this patchset tomorrow.
Regards,
Ryusuke Konishi
> + * @sup: an array of nilfs_suinfo_update structs
> + * @nsup: number of elements in sup
> + */
> +ssize_t nilfs_set_suinfo(const struct nilfs *nilfs,
> + struct nilfs_suinfo_update *sup, size_t nsup)
> +{
> + struct nilfs_argv argv;
> +
> + if (nilfs->n_iocfd < 0) {
> + errno = EBADF;
> + return -1;
> + }
> +
> + argv.v_base = (unsigned long)sup;
> + argv.v_nmembs = nsup;
> + argv.v_size = sizeof(struct nilfs_suinfo_update);
> + argv.v_index = 0;
> + argv.v_flags = 0;
> + if (ioctl(nilfs->n_iocfd, NILFS_IOCTL_SET_SUINFO, &argv) < 0)
> + return -1;
> + return argv.v_nmembs;
> +}
> +
> +/**
> * nilfs_get_sustat -
> * @nilfs:
> * @sustat:
> --
> 1.8.5.3
>
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