From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3sZdr05KZ0zDsYn for ; Thu, 15 Sep 2016 23:02:56 +1000 (AEST) Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id u8FCxMm0084607 for ; Thu, 15 Sep 2016 09:02:54 -0400 Received: from e23smtp05.au.ibm.com (e23smtp05.au.ibm.com [202.81.31.147]) by mx0b-001b2d01.pphosted.com with ESMTP id 25ftr6w15s-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 15 Sep 2016 09:02:54 -0400 Received: from localhost by e23smtp05.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 15 Sep 2016 23:02:50 +1000 Received: from d23relay06.au.ibm.com (d23relay06.au.ibm.com [9.185.63.219]) by d23dlp01.au.ibm.com (Postfix) with ESMTP id 726312CE8056 for ; Thu, 15 Sep 2016 23:02:48 +1000 (EST) Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay06.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u8FD2mh61573326 for ; Thu, 15 Sep 2016 23:02:48 +1000 Received: from d23av03.au.ibm.com (localhost [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u8FD2lv6032084 for ; Thu, 15 Sep 2016 23:02:48 +1000 From: Madhavan Srinivasan To: benh@kernel.crashing.org, mpe@ellerman.id.au Cc: anton@samba.org, paulus@samba.org, npiggin@gmail.com, linuxppc-dev@lists.ozlabs.org, Madhavan Srinivasan Subject: [PATCH 13/13] powerpc: rewrite local_t using soft_irq Date: Thu, 15 Sep 2016 18:32:03 +0530 In-Reply-To: <1473944523-624-1-git-send-email-maddy@linux.vnet.ibm.com> References: <1473944523-624-1-git-send-email-maddy@linux.vnet.ibm.com> Message-Id: <1473944523-624-14-git-send-email-maddy@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Local atomic operations are fast and highly reentrant per CPU counters. Used for percpu variable updates. Local atomic operations only guarantee variable modification atomicity wrt the CPU which owns the data and these needs to be executed in a preemption safe way. Here is the design of this patch. Since local_* operations are only need to be atomic to interrupts (IIUC), we have two options. Either replay the "op" if interrupted or replay the interrupt after the "op". Initial patchset posted was based on implementing local_* operation based on CR5 which replay's the "op". Patchset had issues in case of rewinding the address pointor from an array. This make the slow patch really slow. Since CR5 based implementation proposed using __ex_table to find the rewind addressr, this rasied concerns about size of __ex_table and vmlinux. https://lists.ozlabs.org/pipermail/linuxppc-dev/2014-December/123115.html But this patch uses, local_irq_pmu_save to soft_disable interrupts (including PMIs). After finishing the "op", local_irq_pmu_restore() called and correspondingly interrupts are replayed if any occured. patch re-write the current local_* functions to use arch_local_irq_disbale. Base flow for each function is { local_irq_pmu_save(flags) load .. store local_irq_pmu_restore(flags) } Reason for the approach is that, currently l[w/d]arx/st[w/d]cx. instruction pair is used for local_* operations, which are heavy on cycle count and they dont support a local variant. So to see whether the new implementation helps, used a modified version of Rusty's benchmark code on local_t. https://lkml.org/lkml/2008/12/16/450 Modifications to Rusty's benchmark code: - Executed only local_t test Here are the values with the patch. Time in ns per iteration Local_t Without Patch With Patch _inc 28 8 _add 28 8 _read 3 3 _add_return 28 7 Currently only asm/local.h has been rewrite, and also the entire change is tested only in PPC64 (pseries guest) and PPC64 host (LE) TODO: - local_cmpxchg and local_xchg needs modification. Signed-off-by: Madhavan Srinivasan --- arch/powerpc/include/asm/local.h | 94 ++++++++++++++++++++++++++++------------ 1 file changed, 66 insertions(+), 28 deletions(-) diff --git a/arch/powerpc/include/asm/local.h b/arch/powerpc/include/asm/local.h index b8da91363864..fb5728abb4e9 100644 --- a/arch/powerpc/include/asm/local.h +++ b/arch/powerpc/include/asm/local.h @@ -3,6 +3,9 @@ #include #include +#include + +#include typedef struct { @@ -14,24 +17,50 @@ typedef struct #define local_read(l) atomic_long_read(&(l)->a) #define local_set(l,i) atomic_long_set(&(l)->a, (i)) -#define local_add(i,l) atomic_long_add((i),(&(l)->a)) -#define local_sub(i,l) atomic_long_sub((i),(&(l)->a)) -#define local_inc(l) atomic_long_inc(&(l)->a) -#define local_dec(l) atomic_long_dec(&(l)->a) +static __inline__ void local_add(long i, local_t *l) +{ + long t; + unsigned long flags; + + local_irq_pmu_save(flags); + __asm__ __volatile__( + PPC_LL" %0,0(%2)\n\ + add %0,%1,%0\n" + PPC_STL" %0,0(%2)\n" + : "=&r" (t) + : "r" (i), "r" (&(l->a.counter))); + local_irq_pmu_restore(flags); +} + +static __inline__ void local_sub(long i, local_t *l) +{ + long t; + unsigned long flags; + + local_irq_pmu_save(flags); + __asm__ __volatile__( + PPC_LL" %0,0(%2)\n\ + subf %0,%1,%0\n" + PPC_STL" %0,0(%2)\n" + : "=&r" (t) + : "r" (i), "r" (&(l->a.counter))); + local_irq_pmu_restore(flags); +} static __inline__ long local_add_return(long a, local_t *l) { long t; + unsigned long flags; + local_irq_pmu_save(flags); __asm__ __volatile__( -"1:" PPC_LLARX(%0,0,%2,0) " # local_add_return\n\ + PPC_LL" %0,0(%2)\n\ add %0,%1,%0\n" - PPC405_ERR77(0,%2) - PPC_STLCX "%0,0,%2 \n\ - bne- 1b" + PPC_STL "%0,0(%2)\n" : "=&r" (t) : "r" (a), "r" (&(l->a.counter)) : "cc", "memory"); + local_irq_pmu_restore(flags); return t; } @@ -41,16 +70,18 @@ static __inline__ long local_add_return(long a, local_t *l) static __inline__ long local_sub_return(long a, local_t *l) { long t; + unsigned long flags; + + local_irq_pmu_save(flags); __asm__ __volatile__( -"1:" PPC_LLARX(%0,0,%2,0) " # local_sub_return\n\ +"1:" PPC_LL" %0,0(%2)\n\ subf %0,%1,%0\n" - PPC405_ERR77(0,%2) - PPC_STLCX "%0,0,%2 \n\ - bne- 1b" + PPC_STL "%0,0(%2)\n" : "=&r" (t) : "r" (a), "r" (&(l->a.counter)) : "cc", "memory"); + local_irq_pmu_restore(flags); return t; } @@ -58,16 +89,17 @@ static __inline__ long local_sub_return(long a, local_t *l) static __inline__ long local_inc_return(local_t *l) { long t; + unsigned long flags; + local_irq_pmu_save(flags); __asm__ __volatile__( -"1:" PPC_LLARX(%0,0,%1,0) " # local_inc_return\n\ +"1:" PPC_LL" %0,0(%1)\n\ addic %0,%0,1\n" - PPC405_ERR77(0,%1) - PPC_STLCX "%0,0,%1 \n\ - bne- 1b" + PPC_STL "%0,0(%1)\n" : "=&r" (t) : "r" (&(l->a.counter)) : "cc", "xer", "memory"); + local_irq_pmu_restore(flags); return t; } @@ -85,20 +117,24 @@ static __inline__ long local_inc_return(local_t *l) static __inline__ long local_dec_return(local_t *l) { long t; + unsigned long flags; + local_irq_pmu_save(flags); __asm__ __volatile__( -"1:" PPC_LLARX(%0,0,%1,0) " # local_dec_return\n\ + PPC_LL" %0,0(%1)\n\ addic %0,%0,-1\n" - PPC405_ERR77(0,%1) - PPC_STLCX "%0,0,%1\n\ - bne- 1b" + PPC_STL "%0,0(%1)\n" : "=&r" (t) : "r" (&(l->a.counter)) : "cc", "xer", "memory"); + local_irq_pmu_restore(flags); return t; } +#define local_inc(l) local_inc_return(l) +#define local_dec(l) local_dec_return(l) + #define local_cmpxchg(l, o, n) \ (cmpxchg_local(&((l)->a.counter), (o), (n))) #define local_xchg(l, n) (xchg_local(&((l)->a.counter), (n))) @@ -115,20 +151,21 @@ static __inline__ long local_dec_return(local_t *l) static __inline__ int local_add_unless(local_t *l, long a, long u) { long t; + unsigned long flags; + local_irq_pmu_save(flags); __asm__ __volatile__ ( -"1:" PPC_LLARX(%0,0,%1,0) " # local_add_unless\n\ + PPC_LL" %0,0(%1)\n\ cmpw 0,%0,%3 \n\ beq- 2f \n\ add %0,%2,%0 \n" - PPC405_ERR77(0,%2) - PPC_STLCX "%0,0,%1 \n\ - bne- 1b \n" + PPC_STL" %0,0(%1) \n" " subf %0,%2,%0 \n\ 2:" : "=&r" (t) : "r" (&(l->a.counter)), "r" (a), "r" (u) : "cc", "memory"); + local_irq_pmu_restore(flags); return t != u; } @@ -145,19 +182,20 @@ static __inline__ int local_add_unless(local_t *l, long a, long u) static __inline__ long local_dec_if_positive(local_t *l) { long t; + unsigned long flags; + local_irq_pmu_save(flags); __asm__ __volatile__( -"1:" PPC_LLARX(%0,0,%1,0) " # local_dec_if_positive\n\ + PPC_LL" %0,0(%1)\n\ cmpwi %0,1\n\ addi %0,%0,-1\n\ blt- 2f\n" - PPC405_ERR77(0,%1) - PPC_STLCX "%0,0,%1\n\ - bne- 1b" + PPC_STL "%0,0(%1)\n" "\n\ 2:" : "=&b" (t) : "r" (&(l->a.counter)) : "cc", "memory"); + local_irq_pmu_restore(flags); return t; } -- 2.7.4