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freebsd/sys/cam/cam_sim.c
Alexander Motin 227d67aa54 Merge CAM locking changes from the projects/camlock branch to radically
reduce lock congestion and improve SMP scalability of the SCSI/ATA stack,
preparing the ground for the coming next GEOM direct dispatch support.

Replace big per-SIM locks with bunch of smaller ones:
 - per-LUN locks to protect device and peripheral drivers state;
 - per-target locks to protect list of LUNs on target;
 - per-bus locks to protect reference counting;
 - per-send queue locks to protect queue of CCBs to be sent;
 - per-done queue locks to protect queue of completed CCBs;
 - remaining per-SIM locks now protect only HBA driver internals.

While holding LUN lock it is allowed (while not recommended for performance
reasons) to take SIM lock.  The opposite acquisition order is forbidden.
All the other locks are leaf locks, that can be taken anywhere, but should
not be cascaded.  Many functions, such as: xpt_action(), xpt_done(),
xpt_async(), xpt_create_path(), etc. are no longer require (but allow) SIM
lock to be held.

To keep compatibility and solve cases where SIM lock can't be dropped, all
xpt_async() calls in addition to xpt_done() calls are queued to completion
threads for async processing in clean environment without SIM lock held.

Instead of single CAM SWI thread, used for commands completion processing
before, use multiple (depending on number of CPUs) threads.  Load balanced
between them using "hash" of the device B:T:L address.

HBA drivers that can drop SIM lock during completion processing and have
sufficient number of completion threads to efficiently scale to multiple
CPUs can use new function xpt_done_direct() to avoid extra context switch.
Make ahci(4) driver to use this mechanism depending on hardware setup.

Sponsored by:	iXsystems, Inc.
MFC after:	2 months
2013-10-21 12:00:26 +00:00

155 lines
3.9 KiB
C

/*-
* Common functions for SCSI Interface Modules (SIMs).
*
* Copyright (c) 1997 Justin T. Gibbs.
* 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,
* without modification, immediately at the beginning of the file.
* 2. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <cam/cam.h>
#include <cam/cam_ccb.h>
#include <cam/cam_sim.h>
#include <cam/cam_queue.h>
#include <cam/cam_xpt.h>
#define CAM_PATH_ANY (u_int32_t)-1
static MALLOC_DEFINE(M_CAMSIM, "CAM SIM", "CAM SIM buffers");
struct cam_devq *
cam_simq_alloc(u_int32_t max_sim_transactions)
{
return (cam_devq_alloc(/*size*/0, max_sim_transactions));
}
void
cam_simq_free(struct cam_devq *devq)
{
cam_devq_free(devq);
}
struct cam_sim *
cam_sim_alloc(sim_action_func sim_action, sim_poll_func sim_poll,
const char *sim_name, void *softc, u_int32_t unit,
struct mtx *mtx, int max_dev_transactions,
int max_tagged_dev_transactions, struct cam_devq *queue)
{
struct cam_sim *sim;
if (mtx == NULL)
return (NULL);
sim = (struct cam_sim *)malloc(sizeof(struct cam_sim),
M_CAMSIM, M_ZERO | M_NOWAIT);
if (sim == NULL)
return (NULL);
sim->sim_action = sim_action;
sim->sim_poll = sim_poll;
sim->sim_name = sim_name;
sim->softc = softc;
sim->path_id = CAM_PATH_ANY;
sim->unit_number = unit;
sim->bus_id = 0; /* set in xpt_bus_register */
sim->max_tagged_dev_openings = max_tagged_dev_transactions;
sim->max_dev_openings = max_dev_transactions;
sim->flags = 0;
sim->refcount = 1;
sim->devq = queue;
sim->mtx = mtx;
if (mtx == &Giant) {
sim->flags |= 0;
callout_init(&sim->callout, 0);
} else {
sim->flags |= CAM_SIM_MPSAFE;
callout_init(&sim->callout, 1);
}
return (sim);
}
void
cam_sim_free(struct cam_sim *sim, int free_devq)
{
int error;
mtx_assert(sim->mtx, MA_OWNED);
sim->refcount--;
if (sim->refcount > 0) {
error = msleep(sim, sim->mtx, PRIBIO, "simfree", 0);
KASSERT(error == 0, ("invalid error value for msleep(9)"));
}
KASSERT(sim->refcount == 0, ("sim->refcount == 0"));
if (free_devq)
cam_simq_free(sim->devq);
free(sim, M_CAMSIM);
}
void
cam_sim_release(struct cam_sim *sim)
{
int lock;
lock = (mtx_owned(sim->mtx) == 0);
if (lock)
CAM_SIM_LOCK(sim);
KASSERT(sim->refcount >= 1, ("sim->refcount >= 1"));
sim->refcount--;
if (sim->refcount == 0)
wakeup(sim);
if (lock)
CAM_SIM_UNLOCK(sim);
}
void
cam_sim_hold(struct cam_sim *sim)
{
int lock;
lock = (mtx_owned(sim->mtx) == 0);
if (lock)
CAM_SIM_LOCK(sim);
KASSERT(sim->refcount >= 1, ("sim->refcount >= 1"));
sim->refcount++;
if (lock)
CAM_SIM_UNLOCK(sim);
}
void
cam_sim_set_path(struct cam_sim *sim, u_int32_t path_id)
{
sim->path_id = path_id;
}