From 8b6e511e51f7e540c8e71022318ee4cc9a4567a7 Mon Sep 17 00:00:00 2001 From: Cliff Wickman Date: Fri, 22 Jun 2012 08:14:59 -0500 Subject: x86/uv: Work around UV2 BAU hangs On SGI's UV2 the BAU (Broadcast Assist Unit) driver can hang under a heavy load. To cure this: - Disable the UV2 extended status mode (see UV2_EXT_SHFT), as this mode changes BAU behavior in more ways then just delivering an extra bit of status. Revert status to just two meaningful bits, like UV1. - Use no IPI-style resets on UV2. Just give up the request for whatever the reason it failed and let it be accomplished with the legacy IPI method. - Use no alternate sending descriptor (the former UV2 workaround bcp->using_desc and handle_uv2_busy() stuff). Just disable the use of the BAU for a period of time in favor of the legacy IPI method when the h/w bug leaves a descriptor busy. -- new tunable: giveup_limit determines the threshold at which a hub is so plugged that it should do all requests with the legacy IPI method for a period of time -- generalize disable_for_congestion() (renamed disable_for_period()) for use whenever a hub should avoid using the BAU for a period of time Also: - Fix find_another_by_swack(), which is part of the UV2 bug workaround - Correct and clarify the statistics (new stats s_overipilimit, s_giveuplimit, s_enters, s_ipifordisabled, s_plugged, s_congested) Signed-off-by: Cliff Wickman Link: http://lkml.kernel.org/r/20120622131459.GC31884@sgi.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/uv/uv_bau.h | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) (limited to 'arch/x86/include/asm/uv') diff --git a/arch/x86/include/asm/uv/uv_bau.h b/arch/x86/include/asm/uv/uv_bau.h index 847c00b721b2..a06983cdc125 100644 --- a/arch/x86/include/asm/uv/uv_bau.h +++ b/arch/x86/include/asm/uv/uv_bau.h @@ -140,6 +140,9 @@ #define IPI_RESET_LIMIT 1 /* after this # consecutive successes, bump up the throttle if it was lowered */ #define COMPLETE_THRESHOLD 5 +/* after this # of giveups (fall back to kernel IPI's) disable the use of + the BAU for a period of time */ +#define GIVEUP_LIMIT 100 #define UV_LB_SUBNODEID 0x10 @@ -166,7 +169,6 @@ #define FLUSH_RETRY_TIMEOUT 2 #define FLUSH_GIVEUP 3 #define FLUSH_COMPLETE 4 -#define FLUSH_RETRY_BUSYBUG 5 /* * tuning the action when the numalink network is extremely delayed @@ -175,7 +177,7 @@ microseconds */ #define CONGESTED_REPS 10 /* long delays averaged over this many broadcasts */ -#define CONGESTED_PERIOD 30 /* time for the bau to be +#define DISABLED_PERIOD 10 /* time for the bau to be disabled, in seconds */ /* see msg_type: */ #define MSG_NOOP 0 @@ -520,7 +522,12 @@ struct ptc_stats { unsigned long s_uv2_wars; /* uv2 workaround, perm. busy */ unsigned long s_uv2_wars_hw; /* uv2 workaround, hiwater */ unsigned long s_uv2_war_waits; /* uv2 workaround, long waits */ - unsigned long s_enters; /* entries to the driver */ + unsigned long s_overipilimit; /* over the ipi reset limit */ + unsigned long s_giveuplimit; /* disables, over giveup limit*/ + unsigned long s_enters; /* entries to the driver */ + unsigned long s_ipifordisabled; /* fall back to IPI; disabled */ + unsigned long s_plugged; /* plugged by h/w bug*/ + unsigned long s_congested; /* giveup on long wait */ /* destination statistics */ unsigned long d_alltlb; /* times all tlb's on this cpu were flushed */ @@ -588,8 +595,7 @@ struct bau_control { int ipi_attempts; int conseccompletes; short nobau; - int baudisabled; - int set_bau_off; + short baudisabled; short cpu; short osnode; short uvhub_cpu; @@ -598,14 +604,16 @@ struct bau_control { short cpus_in_socket; short cpus_in_uvhub; short partition_base_pnode; - short using_desc; /* an index, like uvhub_cpu */ - unsigned int inuse_map; + short busy; /* all were busy (war) */ unsigned short message_number; unsigned short uvhub_quiesce; short socket_acknowledge_count[DEST_Q_SIZE]; cycles_t send_message; + cycles_t period_end; + cycles_t period_time; spinlock_t uvhub_lock; spinlock_t queue_lock; + spinlock_t disable_lock; /* tunables */ int max_concurr; int max_concurr_const; @@ -616,9 +624,9 @@ struct bau_control { int complete_threshold; int cong_response_us; int cong_reps; - int cong_period; - unsigned long clocks_per_100_usec; - cycles_t period_time; + cycles_t disabled_period; + int period_giveups; + int giveup_limit; long period_requests; struct hub_and_pnode *thp; }; -- cgit v1.2.1