Date: Thu, 15 Nov 2018 16:02:45 +0000 (UTC) From: Warner Losh <imp@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r340453 - head/sys/cam Message-ID: <201811151602.wAFG2jjU041028@repo.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: imp Date: Thu Nov 15 16:02:45 2018 New Revision: 340453 URL: https://svnweb.freebsd.org/changeset/base/340453 Log: Add cam_iosched_set_latfcn to set a latency callback for high latency. It's often useful to have a callback when an I/O takes more than a threshold amount of time. This adds the infrastructure for periph devices to register one. One use-case is as a debugging aide when you need a semi-realtime indication of an I/O outlier so you can trigger bus capture gear for vendor analysis. Sponsored by: Netflix, Inc Modified: head/sys/cam/cam_iosched.c head/sys/cam/cam_iosched.h Modified: head/sys/cam/cam_iosched.c ============================================================================== --- head/sys/cam/cam_iosched.c Thu Nov 15 16:02:34 2018 (r340452) +++ head/sys/cam/cam_iosched.c Thu Nov 15 16:02:45 2018 (r340453) @@ -294,6 +294,9 @@ struct cam_iosched_softc { uint32_t this_frac; /* Fraction of a second (1024ths) for this tick */ sbintime_t last_time; /* Last time we ticked */ struct control_loop cl; + sbintime_t max_lat; /* when != 0, if iop latency > max_lat, call max_lat_fcn */ + cam_iosched_latfcn_t latfcn; + void *latarg; #endif }; @@ -1171,9 +1174,24 @@ void cam_iosched_sysctl_init(struct cam_iosched_softc OID_AUTO, "load", CTLFLAG_RD, &isc->load, 0, "scaled load average / 100"); + + SYSCTL_ADD_U64(ctx, n, + OID_AUTO, "latency_trigger", CTLFLAG_RW, + &isc->max_lat, 0, + "Latency treshold to trigger callbacks"); #endif } +void +cam_iosched_set_latfcn(struct cam_iosched_softc *isc, + cam_iosched_latfcn_t fnp, void *argp) +{ +#ifdef CAM_IOSCHED_DYNAMIC + isc->latfcn = fnp; + isc->latarg = argp; +#endif +} + /* * Flush outstanding I/O. Consumers of this library don't know all the * queues we may keep, so this allows all I/O to be flushed in one @@ -1510,10 +1528,21 @@ cam_iosched_bio_complete(struct cam_iosched_softc *isc printf("Completing command with bio_cmd == %#x\n", bp->bio_cmd); } - if (!(bp->bio_flags & BIO_ERROR) && done_ccb != NULL) - cam_iosched_io_metric_update(isc, - cam_iosched_sbintime_t(done_ccb->ccb_h.qos.periph_data), + if (!(bp->bio_flags & BIO_ERROR) && done_ccb != NULL) { + sbintime_t sim_latency; + + sim_latency = cam_iosched_sbintime_t(done_ccb->ccb_h.qos.periph_data); + + cam_iosched_io_metric_update(isc, sim_latency, bp->bio_cmd, bp->bio_bcount); + /* + * Debugging code: allow callbacks to the periph driver when latency max + * is exceeded. This can be useful for triggering external debugging actions. + */ + if (isc->latfcn && isc->max_lat != 0 && sim_latency > isc->max_lat) + isc->latfcn(isc->latarg, sim_latency, bp); + } + #endif return retval; } Modified: head/sys/cam/cam_iosched.h ============================================================================== --- head/sys/cam/cam_iosched.h Thu Nov 15 16:02:34 2018 (r340452) +++ head/sys/cam/cam_iosched.h Thu Nov 15 16:02:45 2018 (r340453) @@ -80,6 +80,8 @@ cam_iosched_sbintime_t(uintptr_t delta) return (sbintime_t)((uint64_t)delta << CAM_IOSCHED_TIME_SHIFT); } +typedef void (*cam_iosched_latfcn_t)(void *, sbintime_t, struct bio *); + int cam_iosched_init(struct cam_iosched_softc **, struct cam_periph *periph); void cam_iosched_fini(struct cam_iosched_softc *); void cam_iosched_sysctl_init(struct cam_iosched_softc *, struct sysctl_ctx_list *, struct sysctl_oid *); @@ -98,6 +100,7 @@ void cam_iosched_set_work_flags(struct cam_iosched_sof void cam_iosched_clr_work_flags(struct cam_iosched_softc *isc, uint32_t flags); void cam_iosched_trim_done(struct cam_iosched_softc *isc); int cam_iosched_bio_complete(struct cam_iosched_softc *isc, struct bio *bp, union ccb *done_ccb); +void cam_iosched_set_latfcn(struct cam_iosched_softc *isc, cam_iosched_latfcn_t, void *); #endif #endif
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201811151602.wAFG2jjU041028>