ACK: [PATCH][SRU Disco] iommu/iova: Separate atomic variables to improve performance

[Connor Kuehl]

On 7/1/19 11:45 AM, Connor Kuehl wrote:
> On 6/14/19 1:57 PM, dann frazier wrote:
>> From: Jinyu Qi <jinyuqi at huawei.com>
>>
>> BugLink: https://bugs.launchpad.net/bugs/1832909
>>
>> In struct iova_domain, there are three atomic variables, the former two
>> are about TLB flush counters which use atomic_add operation, anoter is
>> used to flush timer that use cmpxhg operation.
>> These variables are in the same cache line, so it will cause some
>> performance loss under the condition that many cores call queue_iova
>> function, Let's isolate the two type atomic variables to different
>> cache line to reduce cache line conflict.
>>
>> Cc: Joerg Roedel <joro at 8bytes.org>
>> Signed-off-by: Jinyu Qi <jinyuqi at huawei.com>
>> Signed-off-by: Joerg Roedel <jroedel at suse.de>
>> (cherry picked from commit 14bd9a607f9082e7b5690c27e69072f2aeae0de4)
>> Signed-off-by: dann frazier <dann.frazier at canonical.com>
> 
> Acked-by: Connor Kuehl <connor.kuehl at canonical.com>

Sorry, I meant to put ACK in the e-mail subject.

Acked-by: Connor Kuehl <connor.kuehl at canonical.com>

> 
>> ---
>>  include/linux/iova.h | 16 ++++++++--------
>>  1 file changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/linux/iova.h b/include/linux/iova.h
>> index 0b93bf96693ef..28a5128405f82 100644
>> --- a/include/linux/iova.h
>> +++ b/include/linux/iova.h
>> @@ -76,6 +76,14 @@ struct iova_domain {
>>  	unsigned long	start_pfn;	/* Lower limit for this domain */
>>  	unsigned long	dma_32bit_pfn;
>>  	unsigned long	max32_alloc_size; /* Size of last failed allocation */
>> +	struct iova_fq __percpu *fq;	/* Flush Queue */
>> +
>> +	atomic64_t	fq_flush_start_cnt;	/* Number of TLB flushes that
>> +						   have been started */
>> +
>> +	atomic64_t	fq_flush_finish_cnt;	/* Number of TLB flushes that
>> +						   have been finished */
>> +
>>  	struct iova	anchor;		/* rbtree lookup anchor */
>>  	struct iova_rcache rcaches[IOVA_RANGE_CACHE_MAX_SIZE];	/* IOVA range caches */
>>  
>> @@ -85,14 +93,6 @@ struct iova_domain {
>>  	iova_entry_dtor entry_dtor;	/* IOMMU driver specific destructor for
>>  					   iova entry */
>>  
>> -	struct iova_fq __percpu *fq;	/* Flush Queue */
>> -
>> -	atomic64_t	fq_flush_start_cnt;	/* Number of TLB flushes that
>> -						   have been started */
>> -
>> -	atomic64_t	fq_flush_finish_cnt;	/* Number of TLB flushes that
>> -						   have been finished */
>> -
>>  	struct timer_list fq_timer;		/* Timer to regularily empty the
>>  						   flush-queues */
>>  	atomic_t fq_timer_on;			/* 1 when timer is active, 0
>>
>