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175746eb06
The CIO layer scans for newly available I/O devices by performing a scan of available subchannels using the Store Subchannel (STSCH) instruction. Performing too many STSCH instructions in a tight loop can cause high Hypervisor overhead which can negatively impact the performance of the virtual machine as a whole. A subchannel scan is triggered for example during a hardware event that indicates that a channel path has become available. It is also triggered by the DASD device driver for each device that is set online. This patch reduces the number of STSCH instructions being performed by delaying the start of the actual subchannel scan by 1 second. Multiple scan requests that are scheduled during this time will be merged into a single scan loop. The trade-off consists of a short delay that is introduced between the time that the event is processed and a newly available device becoming usable. This delay should be acceptable since it only affects devices that have not been in use before. Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com> Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
147 lines
4.4 KiB
C
147 lines
4.4 KiB
C
#ifndef _CSS_H
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#define _CSS_H
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#include <linux/mutex.h>
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#include <linux/wait.h>
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#include <linux/workqueue.h>
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#include <linux/device.h>
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#include <linux/types.h>
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#include <asm/cio.h>
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#include <asm/chpid.h>
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#include <asm/schid.h>
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#include "cio.h"
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/*
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* path grouping stuff
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*/
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#define SPID_FUNC_SINGLE_PATH 0x00
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#define SPID_FUNC_MULTI_PATH 0x80
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#define SPID_FUNC_ESTABLISH 0x00
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#define SPID_FUNC_RESIGN 0x40
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#define SPID_FUNC_DISBAND 0x20
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#define SNID_STATE1_RESET 0
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#define SNID_STATE1_UNGROUPED 2
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#define SNID_STATE1_GROUPED 3
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#define SNID_STATE2_NOT_RESVD 0
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#define SNID_STATE2_RESVD_ELSE 2
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#define SNID_STATE2_RESVD_SELF 3
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#define SNID_STATE3_MULTI_PATH 1
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#define SNID_STATE3_SINGLE_PATH 0
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struct path_state {
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__u8 state1 : 2; /* path state value 1 */
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__u8 state2 : 2; /* path state value 2 */
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__u8 state3 : 1; /* path state value 3 */
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__u8 resvd : 3; /* reserved */
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} __attribute__ ((packed));
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struct extended_cssid {
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u8 version;
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u8 cssid;
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} __attribute__ ((packed));
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struct pgid {
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union {
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__u8 fc; /* SPID function code */
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struct path_state ps; /* SNID path state */
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} __attribute__ ((packed)) inf;
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union {
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__u32 cpu_addr : 16; /* CPU address */
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struct extended_cssid ext_cssid;
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} __attribute__ ((packed)) pgid_high;
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__u32 cpu_id : 24; /* CPU identification */
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__u32 cpu_model : 16; /* CPU model */
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__u32 tod_high; /* high word TOD clock */
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} __attribute__ ((packed));
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struct subchannel;
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struct chp_link;
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/**
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* struct css_driver - device driver for subchannels
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* @subchannel_type: subchannel type supported by this driver
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* @drv: embedded device driver structure
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* @irq: called on interrupts
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* @chp_event: called for events affecting a channel path
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* @sch_event: called for events affecting the subchannel
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* @probe: function called on probe
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* @remove: function called on remove
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* @shutdown: called at device shutdown
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* @prepare: prepare for pm state transition
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* @complete: undo work done in @prepare
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* @freeze: callback for freezing during hibernation snapshotting
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* @thaw: undo work done in @freeze
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* @restore: callback for restoring after hibernation
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* @settle: wait for asynchronous work to finish
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*/
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struct css_driver {
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struct css_device_id *subchannel_type;
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struct device_driver drv;
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void (*irq)(struct subchannel *);
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int (*chp_event)(struct subchannel *, struct chp_link *, int);
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int (*sch_event)(struct subchannel *, int);
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int (*probe)(struct subchannel *);
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int (*remove)(struct subchannel *);
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void (*shutdown)(struct subchannel *);
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int (*prepare) (struct subchannel *);
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void (*complete) (struct subchannel *);
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int (*freeze)(struct subchannel *);
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int (*thaw) (struct subchannel *);
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int (*restore)(struct subchannel *);
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int (*settle)(void);
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};
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#define to_cssdriver(n) container_of(n, struct css_driver, drv)
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extern int css_driver_register(struct css_driver *);
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extern void css_driver_unregister(struct css_driver *);
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extern void css_sch_device_unregister(struct subchannel *);
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extern int css_register_subchannel(struct subchannel *);
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extern struct subchannel *css_alloc_subchannel(struct subchannel_id);
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extern struct subchannel *get_subchannel_by_schid(struct subchannel_id);
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extern int css_init_done;
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extern int max_ssid;
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int for_each_subchannel_staged(int (*fn_known)(struct subchannel *, void *),
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int (*fn_unknown)(struct subchannel_id,
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void *), void *data);
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extern int for_each_subchannel(int(*fn)(struct subchannel_id, void *), void *);
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void css_update_ssd_info(struct subchannel *sch);
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struct channel_subsystem {
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u8 cssid;
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int valid;
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struct channel_path *chps[__MAX_CHPID + 1];
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struct device device;
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struct pgid global_pgid;
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struct mutex mutex;
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/* channel measurement related */
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int cm_enabled;
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void *cub_addr1;
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void *cub_addr2;
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/* for orphaned ccw devices */
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struct subchannel *pseudo_subchannel;
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};
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#define to_css(dev) container_of(dev, struct channel_subsystem, device)
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extern struct channel_subsystem *channel_subsystems[];
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/* Helper functions to build lists for the slow path. */
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void css_schedule_eval(struct subchannel_id schid);
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void css_schedule_eval_all(void);
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void css_schedule_eval_all_unreg(unsigned long delay);
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int css_complete_work(void);
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int sch_is_pseudo_sch(struct subchannel *);
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struct schib;
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int css_sch_is_valid(struct schib *);
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extern struct workqueue_struct *cio_work_q;
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void css_wait_for_slow_path(void);
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void css_sched_sch_todo(struct subchannel *sch, enum sch_todo todo);
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#endif
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