Am Wed, 28 Sep 2016 14:38:37 -0700 (PDT)
schrieb Eric Wheeler <bcache@xxxxxxxxxxxxxxxxxx>:
> On Wed, 28 Sep 2016, Kai Krakow wrote:
>
> > Am Mon, 26 Sep 2016 16:17:22 -0700
> > schrieb Eric Wheeler <git@xxxxxxxxxxxxxxxxxx>:
> >
> > > Add support to bcache hinting functions and sysfs to hint by the
> > > ioprio of 'current' which can be configured with `ionice`.
> > >
> > > Cache hinting is configurable by writing 'class,level' pairs to
> > > sysfs. These are the defaults:
> > > echo 2,7 > /sys/block/bcache0/bcache/ioprio_bypass
> > > echo 2,0 > /sys/block/bcache0/bcache/ioprio_writeback
> > >
> > > (-p) IO Class (-n) Class level Action
> > > -----------------------------------------------------
> > > (1) Realtime 0-7 Writeback
> > > (2) Best-effort 0 Writeback
> > > (2) Best-effort 1-6 Original
> > > bcache logic (2) Best-effort 7
> > > Bypass cache (3) Idle n/a
> > > Bypass cache
> > >
> > > See `man ionice` for more ioprio detail.
> >
> > This patch fails to apply on 4.7.5... Is it possible to adapt for
> > that version?
> >
>
> Try this one. It's my 4.1 backport which applies cleanly to 4.7, too.
Thanks, this applies.
I wonder if this also has an effect if I only use deadline scheduler? I
think only cfq uses scheduling hints but even with deadline, processes
know about their io priorities. So, bcache should still be able to use
this even with deadline?
> commit 03d581518c28b9361cfde85922919baa1e430c54
> Author: Eric Wheeler <git@xxxxxxxxxxxxxxxxxx>
> Date: Mon Sep 26 16:17:22 2016 -0700
>
> bcache: introduce ioprio-based bypass/writeback hints
>
> Add support to bcache hinting functions and sysfs to hint by the
> ioprio of 'current' which can be configured with `ionice`.
>
> Cache hinting is configurable by writing 'class,level' pairs to
> sysfs. These are the defaults:
> echo 2,7 > /sys/block/bcache0/bcache/ioprio_bypass
> echo 2,0 > /sys/block/bcache0/bcache/ioprio_writeback
>
> (-c) IO Class (-n) Class level Action
> -----------------------------------------------------
> (1) Realtime 0-7 Writeback
> (2) Best-effort 0 Writeback
> (2) Best-effort 1-6 Original
> bcache logic (2) Best-effort 7
> Bypass cache (3) Idle n/a
> Bypass cache
> See `man ionice` for more ioprio detail.
>
> Signed-off-by: Eric Wheeler <bcache@xxxxxxxxxxxxxxxxxx>
>
> Conflicts:
> drivers/md/bcache/writeback.h
>
> diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
> index 04f7bc2..ff1026f 100644
> --- a/drivers/md/bcache/bcache.h
> +++ b/drivers/md/bcache/bcache.h
> @@ -382,6 +382,9 @@ struct cached_dev {
> unsigned writeback_rate_update_seconds;
> unsigned writeback_rate_d_term;
> unsigned writeback_rate_p_term_inverse;
> +
> + unsigned short ioprio_writeback;
> + unsigned short ioprio_bypass;
> };
>
> enum alloc_reserve {
> diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
> index ab43fad..7b36da3 100644
> --- a/drivers/md/bcache/request.c
> +++ b/drivers/md/bcache/request.c
> @@ -369,6 +369,7 @@ static bool check_should_bypass(struct cached_dev
> *dc, struct bio *bio) unsigned sectors, congested =
> bch_get_congested(c); struct task_struct *task = current;
> struct io *i;
> + struct io_context *ioc;
>
> if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
> c->gc_stats.in_use > CUTOFF_CACHE_ADD ||
> @@ -380,6 +381,18 @@ static bool check_should_bypass(struct
> cached_dev *dc, struct bio *bio) (bio->bi_rw & REQ_WRITE)))
> goto skip;
>
> + /* If process ioprio is lower-or-equal to dc->ioprio_bypass,
> then
> + * hint for bypass. Note that a lower-priority IO class+value
> + * has a greater numeric value. */
> + ioc = get_task_io_context(current, GFP_ATOMIC, NUMA_NO_NODE);
> + if (ioc
> + && ioprio_valid(ioc->ioprio)
> + && ioprio_valid(dc->ioprio_writeback)
> + && ioc->ioprio >= dc->ioprio_bypass) {
> + put_io_context(ioc);
> + return true;
> + }
> +
> if (bio->bi_iter.bi_sector & (c->sb.block_size - 1) ||
> bio_sectors(bio) & (c->sb.block_size - 1)) {
> pr_debug("skipping unaligned io");
> diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
> index b3ff57d..83ac010 100644
> --- a/drivers/md/bcache/sysfs.c
> +++ b/drivers/md/bcache/sysfs.c
> @@ -106,6 +106,9 @@ rw_attribute(btree_shrinker_disabled);
> rw_attribute(copy_gc_enabled);
> rw_attribute(size);
>
> +rw_attribute(ioprio_writeback);
> +rw_attribute(ioprio_bypass);
> +
> SHOW(__bch_cached_dev)
> {
> struct cached_dev *dc = container_of(kobj, struct cached_dev,
> @@ -182,6 +185,17 @@ SHOW(__bch_cached_dev)
> return strlen(buf);
> }
>
> + if (attr == &sysfs_ioprio_bypass)
> + return snprintf(buf, PAGE_SIZE-1, "%d,%ld\n",
> + IOPRIO_PRIO_CLASS(dc->ioprio_bypass),
> + IOPRIO_PRIO_DATA(dc->ioprio_bypass));
> +
> + if (attr == &sysfs_ioprio_writeback)
> + return snprintf(buf, PAGE_SIZE-1, "%d,%ld\n",
> + IOPRIO_PRIO_CLASS(dc->ioprio_writeback),
> + IOPRIO_PRIO_DATA(dc->ioprio_writeback));
> +
> +
> #undef var
> return 0;
> }
> @@ -194,6 +208,8 @@ STORE(__cached_dev)
> unsigned v = size;
> struct cache_set *c;
> struct kobj_uevent_env *env;
> + unsigned ioprio_class = 0; /* invalid initial ioprio values
> */
> + unsigned ioprio_value = IOPRIO_BE_NR+1;
>
> #define d_strtoul(var) sysfs_strtoul(var, dc->var)
> #define d_strtoul_nonzero(var) sysfs_strtoul_clamp(var,
> dc->var, 1, INT_MAX) @@ -282,6 +298,33 @@ STORE(__cached_dev)
> if (attr == &sysfs_stop)
> bcache_device_stop(&dc->disk);
>
> + if (attr == &sysfs_ioprio_writeback) {
> + if (sscanf(buf, "%u,%u", &ioprio_class,
> &ioprio_value) != 2
> + || ioprio_class > IOPRIO_CLASS_IDLE
> + || ioprio_class < IOPRIO_CLASS_RT
> + || ioprio_value >= IOPRIO_BE_NR)
> + pr_err("bcache: ioprio_writeback invalid
> ioprio class: %u data value: %u\n",
> + ioprio_class, ioprio_value);
> + else if (ioprio_class == IOPRIO_CLASS_IDLE)
> + dc->ioprio_writeback =
> IOPRIO_PRIO_VALUE(ioprio_class, 0);
> + else
> + dc->ioprio_writeback =
> IOPRIO_PRIO_VALUE(ioprio_class, ioprio_value);
> + }
> +
> + if (attr == &sysfs_ioprio_bypass)
> + {
> + if (sscanf(buf, "%u,%u", &ioprio_class,
> &ioprio_value) != 2
> + || ioprio_class > IOPRIO_CLASS_IDLE
> + || ioprio_class < IOPRIO_CLASS_RT
> + || ioprio_value >= IOPRIO_BE_NR)
> + pr_err("bcache: ioprio_bypass invalid ioprio
> class: %u data value: %u\n",
> + ioprio_class, ioprio_value);
> + else if (ioprio_class == IOPRIO_CLASS_IDLE)
> + dc->ioprio_writeback =
> IOPRIO_PRIO_VALUE(ioprio_class, 0);
> + else
> + dc->ioprio_writeback =
> IOPRIO_PRIO_VALUE(ioprio_class, ioprio_value);
> + }
> +
> return size;
> }
>
> @@ -334,6 +377,8 @@ static struct attribute *bch_cached_dev_files[] =
> { &sysfs_verify,
> &sysfs_bypass_torture_test,
> #endif
> + &sysfs_ioprio_bypass,
> + &sysfs_ioprio_writeback,
> NULL
> };
> KTYPE(bch_cached_dev);
> diff --git a/drivers/md/bcache/writeback.c
> b/drivers/md/bcache/writeback.c index f1986bc..cc2c7ae 100644
> --- a/drivers/md/bcache/writeback.c
> +++ b/drivers/md/bcache/writeback.c
> @@ -494,6 +494,9 @@ void bch_cached_dev_writeback_init(struct
> cached_dev *dc) dc->writeback_rate_d_term = 30;
> dc->writeback_rate_p_term_inverse = 6000;
>
> + dc->ioprio_writeback = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, 0);
> + dc->ioprio_bypass = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE,
> IOPRIO_BE_NR-1); +
> INIT_DELAYED_WORK(&dc->writeback_rate_update,
> update_writeback_rate); }
>
> diff --git a/drivers/md/bcache/writeback.h
> b/drivers/md/bcache/writeback.h index 0a9dab1..defd168 100644
> --- a/drivers/md/bcache/writeback.h
> +++ b/drivers/md/bcache/writeback.h
> @@ -43,6 +43,7 @@ static inline bool should_writeback(struct
> cached_dev *dc, struct bio *bio, unsigned cache_mode, bool would_skip)
> {
> unsigned in_use = dc->disk.c->gc_stats.in_use;
> + struct io_context *ioc;
>
> if (cache_mode != CACHE_MODE_WRITEBACK ||
> test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
> @@ -57,6 +58,18 @@ static inline bool should_writeback(struct
> cached_dev *dc, struct bio *bio, if (would_skip)
> return false;
>
> + /* If process ioprio is higher-or-equal to
> dc->ioprio_writeback, then
> + * hint for writeback. Note that a higher-priority IO
> class+value
> + * has a lesser numeric value. */
> + ioc = get_task_io_context(current, GFP_ATOMIC, NUMA_NO_NODE);
> + if (ioc
> + && ioprio_valid(ioc->ioprio)
> + && ioprio_valid(dc->ioprio_writeback)
> + && ioc->ioprio <= dc->ioprio_writeback) {
> + put_io_context(ioc);
> + return true;
> + }
> +
> return bio->bi_rw & REQ_SYNC ||
> in_use <= CUTOFF_WRITEBACK;
> }
>
--
Regards,
Kai
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