Date: Fri, 9 Jan 2009 11:48:53 +0000 (UTC) From: Luigi Rizzo <luigi@FreeBSD.org> To: src-committers@freebsd.org, svn-src-user@freebsd.org Subject: svn commit: r186945 - in user/luigi/geom_sched: sbin/geom/class/sched sys/geom sys/geom/sched Message-ID: <200901091148.n09BmrlE055970@svn.freebsd.org>
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Author: luigi Date: Fri Jan 9 11:48:53 2009 New Revision: 186945 URL: http://svn.freebsd.org/changeset/base/186945 Log: documentation and small reorganization of the code Modified: user/luigi/geom_sched/sbin/geom/class/sched/gsched.8 user/luigi/geom_sched/sys/geom/geom_sched.c user/luigi/geom_sched/sys/geom/sched/g_rr.c Modified: user/luigi/geom_sched/sbin/geom/class/sched/gsched.8 ============================================================================== --- user/luigi/geom_sched/sbin/geom/class/sched/gsched.8 Fri Jan 9 11:47:14 2009 (r186944) +++ user/luigi/geom_sched/sbin/geom/class/sched/gsched.8 Fri Jan 9 11:48:53 2009 (r186945) @@ -27,7 +27,7 @@ .Os .Sh NAME .Nm gsched -.Nd "control utility for SCHED GEOM class" +.Nd "control utility for disk scheduler GEOM class" .Sh SYNOPSIS .Nm .Cm create @@ -46,13 +46,7 @@ .Op Fl v .Ar prov ... .Nm -.Cm list -.Nm -.Cm status -.Nm -.Cm load -.Nm -.Cm unload +.Cm { list | status | load | unload } .Sh DESCRIPTION The .Nm @@ -121,8 +115,8 @@ The following example shows how to creat .Pa /dev/da0 , and how to destroy it. .Bd -literal -offset indent -gnop create -v da0 -gnop destroy -v da0.nop +gsched create -v da0 +gsched destroy -v da0.nop .Ed .Pp .Ed Modified: user/luigi/geom_sched/sys/geom/geom_sched.c ============================================================================== --- user/luigi/geom_sched/sys/geom/geom_sched.c Fri Jan 9 11:47:14 2009 (r186944) +++ user/luigi/geom_sched/sys/geom/geom_sched.c Fri Jan 9 11:48:53 2009 (r186945) @@ -24,6 +24,14 @@ * SUCH DAMAGE. */ +/* + * This file implements the glue for device-level pluggable disk schedulers. + * The actual scheduling policy is implemented by external modules which + * register with this one, e.g. gs_as or gs_rr ... + * Functions defined here are exported to geom_disk and to individual + * device drivers. XXX to be completed + */ + #include <sys/cdefs.h> #include <sys/param.h> @@ -46,12 +54,17 @@ /* Debug sysctl stuff. */ SYSCTL_DECL(_kern_geom); -SYSCTL_NODE(_kern_geom, OID_AUTO, sched, CTLFLAG_RW, 0, "I/O scheduler stuff"); -u_int g_sched_debug; +SYSCTL_NODE(_kern_geom, OID_AUTO, sched, CTLFLAG_RW, 0, + "Disk I/O scheduler"); +u_int g_sched_debug; /* also used by children modules */ SYSCTL_UINT(_kern_geom_sched, OID_AUTO, debug, CTLFLAG_RW, &g_sched_debug, 0, "Debug level"); /* + * The variables below store the list of schedulers registered + * with this class. A scheduler registers through the DECLARE_GSCHED_MODULE + * macro which in eventually causes the invocation of g_sched_register(). + * * Global mutex, protecting the registered schedulers' list and their * gs_refs field. */ @@ -102,9 +115,9 @@ g_sched_disk_init(struct disk *dp) } /* - * Flush the scheduler, assuming that the disk d_sched_lock mutex is - * held. This function tries to dispatch all the requests queued in - * the target scheduler and to wait until they're completed. Flushing + * Flush the scheduler. Called with the disk d_sched_lock mutex held. + * This function tries to dispatch all the requests queued in + * the target scheduler and to wait until they are completed. Flushing * is implemented avoiding queueing for all the requests arriving while * the flush is in progres. */ @@ -129,6 +142,11 @@ g_sched_flush_locked(struct disk *dp) dp->d_sched_flags &= ~G_SCHED_FLUSHING; } +/* + * This function is called by geom_disk when a disk has been detached. + * We may have requests still queued, and need to dispose them because + * there is no underlying device anymore. + */ void g_sched_disk_gone(struct disk *dp) { @@ -145,6 +163,7 @@ g_sched_disk_gone(struct disk *dp) * an appropriate error. Need to release the disk * lock since completion callbacks may reenter the * scheduler. + * gsp should remain unchanged across the loop. */ biofinish(bp, NULL, ENXIO); mtx_lock(&dp->d_sched_lock); @@ -159,8 +178,9 @@ g_sched_disk_fini(struct disk *dp) g_sched_disk_gone(dp); /* - * Here we assume that no new requests reach the scheduler, since - * the disk is almost already destroyed. + * No new requests can reach the scheduler, as the disk + * is almost already destroyed (almost meaning that no more + * requests should arrive and the queue is empty). */ g_sched_configure(dp, "none"); mtx_destroy(&dp->d_sched_lock); @@ -175,45 +195,36 @@ g_sched_start(struct disk *dp, struct bi gsp = dp->d_sched; /* - * Don't try to queue a request if we have no scheduler for - * this disk, or if the request is not one of the type we care - * about (i.e., it is not a read or write). - */ - if (gsp == NULL || (bp->bio_cmd & (BIO_READ | BIO_WRITE)) == 0) - goto nosched; - - /* - * When flushing is in progress we don't want the scheduler - * queue to grow, so we dispatch new requests directly to the - * driver. - */ - if ((dp->d_sched_flags & G_SCHED_FLUSHING) != 0) - goto nosched; - - dp->d_nr_sorted++; - gsp->gs_start(dp->d_sched_data, bp); - mtx_unlock(&dp->d_sched_lock); - - /* - * Try to immediately start the queue. It is up to the scheduler - * to freeze it if needed (returning NULL on the next invocation - * of gs_next()). The scheduler will also be responsible of - * restarting the dispatches to the driver, invoking d_kick() - * directly. - */ - dp->d_kick(dp); - return; + * Only queue a request if + * 1. we have a scheduler (gsp != NULL); + * 2. this is a read or write request; + * 3. we are not flushing the scheduler. + * In all other cases, dispatch directly to the driver. + */ + if (gsp != NULL && (bp->bio_cmd & (BIO_READ | BIO_WRITE)) != 0 && + (dp->d_sched_flags & G_SCHED_FLUSHING) == 0) { + dp->d_nr_sorted++; + gsp->gs_start(dp->d_sched_data, bp); + mtx_unlock(&dp->d_sched_lock); -nosched: - mtx_unlock(&dp->d_sched_lock); + /* + * Try to immediately start the queue. It is up to + * the scheduler to freeze it if needed (returning NULL + * on the next invocation of gs_next()). In this case + * the scheduler will also be in charge of restarting + * the dispatches to the driver, invoking d_kick() + * directly. + */ + dp->d_kick(dp); + } else { + mtx_unlock(&dp->d_sched_lock); - /* - * Mark the request as not sorted by the scheduler. Schedulers - * are supposed to store a non-NULL value in the bio_caller1 field - * (they will need it anyway, unless they're really really simple.) - */ - bp->bio_caller1 = NULL; - dp->d_strategy(bp); + /* + * Mark the request as not sorted by the scheduler. + */ + bp->bio_caller1 = NULL; + dp->d_strategy(bp); + } } struct bio * @@ -227,18 +238,14 @@ g_sched_next(struct disk *dp) mtx_lock(&dp->d_sched_lock); gsp = dp->d_sched; - /* If the disk is not using a scheduler, just always return NULL. */ - if (gsp == NULL) - goto out; - - /* Get the next request from the scheduler. */ - bp = gsp->gs_next(dp->d_sched_data, - (dp->d_sched_flags & G_SCHED_FLUSHING) != 0); + if (gsp != NULL) { /* make sure we have a scheduler */ + /* Get the next request from the scheduler. */ + bp = gsp->gs_next(dp->d_sched_data, + (dp->d_sched_flags & G_SCHED_FLUSHING) != 0); - KASSERT(bp == NULL || bp->bio_caller1 != NULL, - ("bio_caller1 == NULL")); - -out: + KASSERT(bp == NULL || bp->bio_caller1 != NULL, + ("bio_caller1 == NULL")); + } mtx_unlock(&dp->d_sched_lock); return (bp); @@ -262,22 +269,19 @@ g_sched_done(struct bio *bp) * Don't call the completion callback if we have no scheduler * or if the request that completed was not one we sorted. */ - if (gsp == NULL || bp->bio_caller1 == NULL) - goto out; - - kick = gsp->gs_done(dp->d_sched_data, bp); + if (gsp != NULL && bp->bio_caller1 != NULL) { + kick = gsp->gs_done(dp->d_sched_data, bp); - /* - * If flush is in progress and we have no more requests queued, - * wake up the flushing process. - */ - if (--dp->d_nr_sorted == 0 && - (dp->d_sched_flags & G_SCHED_FLUSHING) != 0) { - G_SCHED_DEBUG(2, "geom_sched: flush complete"); - wakeup(&dp->d_sched); + /* + * If flush is in progress and we have no more requests queued, + * wake up the flushing process. + */ + if (--dp->d_nr_sorted == 0 && + (dp->d_sched_flags & G_SCHED_FLUSHING) != 0) { + G_SCHED_DEBUG(2, "geom_sched: flush complete"); + wakeup(&dp->d_sched); + } } - -out: mtx_unlock(&dp->d_sched_lock); if (kick) @@ -333,13 +337,14 @@ g_sched_unregister(struct g_sched *gsp) G_SCHED_DEBUG(1, "geom_sched: %s still in use", gsp->gs_name); error = EBUSY; - } else if (gsp->gs_refs == 1) + } else if (gsp->gs_refs == 1) { /* * The list reference is the last one * that can be removed, so it is safe to * just decrement the counter elsewhere. */ LIST_REMOVE(gsp, gs_list); + } goto out; } } Modified: user/luigi/geom_sched/sys/geom/sched/g_rr.c ============================================================================== --- user/luigi/geom_sched/sys/geom/sched/g_rr.c Fri Jan 9 11:47:14 2009 (r186944) +++ user/luigi/geom_sched/sys/geom/sched/g_rr.c Fri Jan 9 11:48:53 2009 (r186945) @@ -24,6 +24,10 @@ * SUCH DAMAGE. */ +/* + * GEOM-based round robin disk scheduler. + */ + #include <sys/param.h> #include <sys/systm.h> #include <sys/kernel.h> @@ -43,7 +47,7 @@ */ /* Timeout for anticipation. */ -#define G_RR_WAIT_EXPIRE (hz/200 > 0 ? hz/200 : 2) +#define G_RR_WAIT_EXPIRE (hz/400 > 0 ? hz/200 : 2) #define G_QUEUE_NOWAIT 0 /* Ready to dispatch. */ #define G_QUEUE_WAITREQ 1 /* Waiting for a completion. */ @@ -129,6 +133,7 @@ g_rr_queue_get(struct g_rr_softc *sc, u_ bioq_init(&qp->q_bioq); qp->q_budget = G_RR_DEFAULT_BUDGET; LIST_INSERT_HEAD(bucket, qp, q_hash); + printf("new queue for key %lu\n", key); } return (qp); @@ -177,7 +182,6 @@ g_rr_fini(void *data) KASSERT(TAILQ_EMPTY(&sc->sc_rr_tailq), ("still scheduled queues")); for (i = 0; i < G_RR_HASH_SIZE; i++) { LIST_FOREACH_SAFE(qp, &sc->sc_hash[i], q_hash, qp2) { - LIST_REMOVE(qp, q_hash); g_rr_queue_put(qp); } } @@ -246,6 +250,9 @@ g_rr_dispatch(struct g_rr_softc *sc) g_io_request(bp, LIST_FIRST(&sc->sc_geom->consumer)); } +/* + * Called when a real request for disk I/O arrives. + */ static void g_rr_start(void *data, struct bio *bp) {
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