Date: Tue, 21 Apr 2020 16:52:57 +0000 (UTC) From: Alexander Motin <mav@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r360156 - stable/12/sys/dev/ipmi Message-ID: <202004211652.03LGqv3l087087@repo.freebsd.org>
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Author: mav Date: Tue Apr 21 16:52:56 2020 New Revision: 360156 URL: https://svnweb.freebsd.org/changeset/base/360156 Log: MFC r348996 (by jtl): The current IPMI KCS code is waiting 100us for all transitions (roughly between each byte either sent or received). However, most transitions actually complete in 2-3 microseconds. By polling the status register with a delay of 4us with exponential backoff, the performance of most IPMI operations is significantly improved: - A BMC update on a Supermicro x9 or x11 motherboard goes from ~1 hour to ~6-8 minutes. - An ipmitool sensor list time improves by a factor of 4. Testing showed no significant improvements on a modern server by using a lower delay. The changes should also generally reduce the total amount of CPU or I/O bandwidth used for a given IPMI operation. Modified: stable/12/sys/dev/ipmi/ipmi_kcs.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/dev/ipmi/ipmi_kcs.c ============================================================================== --- stable/12/sys/dev/ipmi/ipmi_kcs.c Tue Apr 21 16:13:22 2020 (r360155) +++ stable/12/sys/dev/ipmi/ipmi_kcs.c Tue Apr 21 16:52:56 2020 (r360156) @@ -48,55 +48,46 @@ __FBSDID("$FreeBSD$"); #include <dev/ipmi/ipmivars.h> #endif +#define POLLING_DELAY_MIN 4 /* Waits are 2-3 usecs on typical systems */ +#define POLLING_DELAY_MAX 256 + static void kcs_clear_obf(struct ipmi_softc *, int); static void kcs_error(struct ipmi_softc *); -static int kcs_wait_for_ibf(struct ipmi_softc *, int); -static int kcs_wait_for_obf(struct ipmi_softc *, int); +static int kcs_wait_for_ibf(struct ipmi_softc *, bool); +static int kcs_wait_for_obf(struct ipmi_softc *, bool); static int -kcs_wait_for_ibf(struct ipmi_softc *sc, int state) +kcs_wait(struct ipmi_softc *sc, int value, int mask) { int status, start = ticks; + int delay_usec = POLLING_DELAY_MIN; status = INB(sc, KCS_CTL_STS); - if (state == 0) { - /* WAIT FOR IBF = 0 */ - while (ticks - start < MAX_TIMEOUT && status & KCS_STATUS_IBF) { - DELAY(100); - status = INB(sc, KCS_CTL_STS); - } - } else { - /* WAIT FOR IBF = 1 */ - while (ticks - start < MAX_TIMEOUT && - !(status & KCS_STATUS_IBF)) { - DELAY(100); - status = INB(sc, KCS_CTL_STS); - } + while (ticks - start < MAX_TIMEOUT && (status & mask) != value) { + /* + * The wait delay is increased exponentially to avoid putting + * significant load on I/O bus. + */ + DELAY(delay_usec); + status = INB(sc, KCS_CTL_STS); + if (delay_usec < POLLING_DELAY_MAX) + delay_usec *= 2; } return (status); } static int -kcs_wait_for_obf(struct ipmi_softc *sc, int state) +kcs_wait_for_ibf(struct ipmi_softc *sc, bool level) { - int status, start = ticks; - status = INB(sc, KCS_CTL_STS); - if (state == 0) { - /* WAIT FOR OBF = 0 */ - while (ticks - start < MAX_TIMEOUT && status & KCS_STATUS_OBF) { - DELAY(100); - status = INB(sc, KCS_CTL_STS); - } - } else { - /* WAIT FOR OBF = 1 */ - while (ticks - start < MAX_TIMEOUT && - !(status & KCS_STATUS_OBF)) { - DELAY(100); - status = INB(sc, KCS_CTL_STS); - } - } - return (status); + return (kcs_wait(sc, level ? KCS_STATUS_IBF : 0, KCS_STATUS_IBF)); +} + +static int +kcs_wait_for_obf(struct ipmi_softc *sc, bool level) +{ + + return (kcs_wait(sc, level ? KCS_STATUS_OBF : 0, KCS_STATUS_OBF)); } static void
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