freebsd-skq/sys/geom/sched/gs_delay.c

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/*-
* Copyright (c) 2015 Netflix, Inc.
*
* Derived from gs_rr.c:
* Copyright (c) 2009-2010 Fabio Checconi
* Copyright (c) 2009-2010 Luigi Rizzo, Universita` di Pisa
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* $Id$
* $FreeBSD$
*
* A simple scheduler that just delays certain transactions by a certain
* amount. We collect all the transactions that are 'done' and put them on
* a queue. The queue is run through every so often and the transactions that
* have taken longer than the threshold delay are completed.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/bio.h>
#include <sys/callout.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/proc.h>
#include <sys/queue.h>
#include <sys/sbuf.h>
#include <sys/sysctl.h>
#include "gs_scheduler.h"
/* Useful constants */
#define BTFRAC_1US 18446744073709ULL /* 2^64 / 1000000 */
/* list of scheduler instances */
LIST_HEAD(g_scheds, g_delay_softc);
/*
* Per device descriptor, holding the Round Robin list of queues
* accessing the disk, a reference to the geom, and the timer.
*/
struct g_delay_softc {
struct g_geom *sc_geom;
struct bio_queue_head sc_bioq; /* queue of pending requests */
struct callout sc_wait; /* timer for completing with delays */
/* Statistics */
int sc_in_flight; /* requests in the driver */
};
/*
* parameters, config and stats
*/
struct g_delay_params {
uint64_t io;
int bypass; /* bypass scheduling */
int units; /* how many instances */
int latency; /* How big a latncy are hoping for */
};
static struct g_delay_params me = {
.bypass = 0,
.units = 0,
.latency = 0,
.io = 0,
};
struct g_delay_params *gs_delay_me = &me;
SYSCTL_DECL(_kern_geom_sched);
static SYSCTL_NODE(_kern_geom_sched, OID_AUTO, delay, CTLFLAG_RW, 0,
"GEOM_SCHED DELAY stuff");
SYSCTL_INT(_kern_geom_sched_delay, OID_AUTO, bypass, CTLFLAG_RD,
&me.bypass, 0, "Scheduler bypass");
SYSCTL_INT(_kern_geom_sched_delay, OID_AUTO, units, CTLFLAG_RD,
&me.units, 0, "Scheduler instances");
SYSCTL_INT(_kern_geom_sched_delay, OID_AUTO, latency, CTLFLAG_RW,
&me.latency, 0, "Minimum latency for requests, in microseconds (1/hz resolution)");
SYSCTL_QUAD(_kern_geom_sched_delay, OID_AUTO, io, CTLFLAG_RW,
&me.io, 0, "I/Os delayed\n");
static int
g_delay_init_class(void *data, void *priv)
{
return (0);
}
static void
g_delay_fini_class(void *data, void *priv)
{
}
/*
* Called on a request arrival, timeout or completion.
* Try to serve a request among those queued.
*/
static struct bio *
g_delay_next(void *data, int force)
{
struct g_delay_softc *sc = data;
struct bio *bp;
struct bintime bt;
bp = bioq_first(&sc->sc_bioq);
if (bp == NULL)
return (NULL);
/*
* If the time isn't yet ripe for this bp to be let loose,
* then the time isn't ripe for any of its friends either
* since we insert in-order. Terminate if the bio hasn't
* aged appropriately. Note that there's pathology here
* such that we may be up to one tick early in releasing
* this I/O. We could implement this up to a tick late too
* but choose not to.
*/
getbinuptime(&bt); /* BIO's bio_t0 is uptime */
if (bintime_cmp(&bp->bio_t0, &bt, >))
return (NULL);
me.io++;
/*
* The bp has mellowed enough, let it through and update stats.
* If there's others, we'll catch them next time we get called.
*/
sc->sc_in_flight++;
bp = bioq_takefirst(&sc->sc_bioq);
return (bp);
}
/*
* Called when a real request for disk I/O arrives.
* Locate the queue associated with the client.
* If the queue is the one we are anticipating for, reset its timeout;
* if the queue is not in the round robin list, insert it in the list.
* On any error, do not queue the request and return -1, the caller
* will take care of this request.
*/
static int
g_delay_start(void *data, struct bio *bp)
{
struct g_delay_softc *sc = data;
if (me.bypass)
return (-1); /* bypass the scheduler */
bp->bio_caller1 = sc;
getbinuptime(&bp->bio_t0); /* BIO's bio_t0 is uptime */
bintime_addx(&bp->bio_t0, BTFRAC_1US * me.latency);
/*
* Keep the I/Os ordered. Lower layers will reorder as we release them down.
* We rely on this in g_delay_next() so that we delay all things equally. Even
* if we move to multiple queues to push stuff down the stack, we'll want to
* insert in order and let the lower layers do whatever reordering they want.
*/
bioq_insert_tail(&sc->sc_bioq, bp);
return (0);
}
static void
g_delay_timeout(void *data)
{
struct g_delay_softc *sc = data;
g_sched_lock(sc->sc_geom);
g_sched_dispatch(sc->sc_geom);
g_sched_unlock(sc->sc_geom);
callout_reset(&sc->sc_wait, 1, g_delay_timeout, sc);
}
/*
* Module glue: allocate descriptor, initialize its fields.
*/
static void *
g_delay_init(struct g_geom *geom)
{
struct g_delay_softc *sc;
/* XXX check whether we can sleep */
sc = malloc(sizeof *sc, M_GEOM_SCHED, M_NOWAIT | M_ZERO);
sc->sc_geom = geom;
bioq_init(&sc->sc_bioq);
callout_init(&sc->sc_wait, CALLOUT_MPSAFE);
callout_reset(&sc->sc_wait, 1, g_delay_timeout, sc);
me.units++;
return (sc);
}
/*
* Module glue -- drain the callout structure, destroy the
* hash table and its element, and free the descriptor.
*/
static void
g_delay_fini(void *data)
{
struct g_delay_softc *sc = data;
/* We're force drained before getting here */
/* Kick out timers */
callout_drain(&sc->sc_wait);
me.units--;
free(sc, M_GEOM_SCHED);
}
/*
* Called when the request under service terminates.
* Start the anticipation timer if needed.
*/
static void
g_delay_done(void *data, struct bio *bp)
{
struct g_delay_softc *sc = data;
sc->sc_in_flight--;
g_sched_dispatch(sc->sc_geom);
}
static void
g_delay_dumpconf(struct sbuf *sb, const char *indent, struct g_geom *gp,
struct g_consumer *cp, struct g_provider *pp)
{
}
static struct g_gsched g_delay = {
.gs_name = "delay",
.gs_priv_size = 0,
.gs_init = g_delay_init,
.gs_fini = g_delay_fini,
.gs_start = g_delay_start,
.gs_done = g_delay_done,
.gs_next = g_delay_next,
.gs_dumpconf = g_delay_dumpconf,
.gs_init_class = g_delay_init_class,
.gs_fini_class = g_delay_fini_class,
};
DECLARE_GSCHED_MODULE(delay, &g_delay);