From 449666dd1efacaf3f0eb020cc617dd702356575c Mon Sep 17 00:00:00 2001 From: Peter Oberparleiter Date: Tue, 26 Nov 2013 14:55:56 +0100 Subject: [PATCH] s390/cio: More efficient handling of CHPID availability events The CIO layer processes hardware events that indicate that a channel path has become available 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. This patch reduces the number of STSCH instructions performed while processing a resource accessibility event and while varying a CHPID online. In both cases, Linux first performs a STSCH instruction on each unused subchannel to see if the subchannel has become available. If the STSCH instruction indicates that the subchannel is available, a full evaluation of this subchannel is scheduled. Since the full evaluation includes performing a STSCH instruction, the initial STSCH is unnecessary and can be removed. Signed-off-by: Peter Oberparleiter Reviewed-by: Sebastian Ott Signed-off-by: Martin Schwidefsky --- drivers/s390/cio/chsc.c | 40 ++++------------------------------------ 1 file changed, 4 insertions(+), 36 deletions(-) diff --git a/drivers/s390/cio/chsc.c b/drivers/s390/cio/chsc.c index 13299f9..eee70cb 100644 --- a/drivers/s390/cio/chsc.c +++ b/drivers/s390/cio/chsc.c @@ -237,26 +237,6 @@ void chsc_chp_offline(struct chp_id chpid) for_each_subchannel_staged(s390_subchannel_remove_chpid, NULL, &link); } -static int s390_process_res_acc_new_sch(struct subchannel_id schid, void *data) -{ - struct schib schib; - /* - * We don't know the device yet, but since a path - * may be available now to the device we'll have - * to do recognition again. - * Since we don't have any idea about which chpid - * that beast may be on we'll have to do a stsch - * on all devices, grr... - */ - if (stsch_err(schid, &schib)) - /* We're through */ - return -ENXIO; - - /* Put it on the slow path. */ - css_schedule_eval(schid); - return 0; -} - static int __s390_process_res_acc(struct subchannel *sch, void *data) { spin_lock_irq(sch->lock); @@ -287,8 +267,8 @@ static void s390_process_res_acc(struct chp_link *link) * The more information we have (info), the less scanning * will we have to do. */ - for_each_subchannel_staged(__s390_process_res_acc, - s390_process_res_acc_new_sch, link); + for_each_subchannel_staged(__s390_process_res_acc, NULL, link); + css_schedule_reprobe(); } static int @@ -663,19 +643,6 @@ static int s390_subchannel_vary_chpid_on(struct subchannel *sch, void *data) return 0; } -static int -__s390_vary_chpid_on(struct subchannel_id schid, void *data) -{ - struct schib schib; - - if (stsch_err(schid, &schib)) - /* We're through */ - return -ENXIO; - /* Put it on the slow path. */ - css_schedule_eval(schid); - return 0; -} - /** * chsc_chp_vary - propagate channel-path vary operation to subchannels * @chpid: channl-path ID @@ -694,7 +661,8 @@ int chsc_chp_vary(struct chp_id chpid, int on) /* Try to update the channel path description. */ chp_update_desc(chp); for_each_subchannel_staged(s390_subchannel_vary_chpid_on, - __s390_vary_chpid_on, &chpid); + NULL, &chpid); + css_schedule_reprobe(); } else for_each_subchannel_staged(s390_subchannel_vary_chpid_off, NULL, &chpid); -- 2.7.4