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From:   Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH 5/5] mm/hugetl.c: warn out if expected count of huge pages
 adjustment is not achieved
To:     Baoquan He <bhe@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        akpm@linux-foundation.org
References: <20200720062623.13135-1-bhe@redhat.com>
 <20200720062623.13135-6-bhe@redhat.com>
 <c5eb3692-2d05-d6dc-437d-21e51705560e@oracle.com>
 <20200722084913.GO32539@MiWiFi-R3L-srv>
Message-ID: <05d5dfde-4c1f-8f62-9526-a9a81c5ffdc1@oracle.com>
Date:   Wed, 22 Jul 2020 09:15:58 -0700
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On 7/22/20 1:49 AM, Baoquan He wrote:
> On 07/20/20 at 05:38pm, Mike Kravetz wrote:
>>> +	if (count != h->max_huge_pages) {
>>> +		char buf[32];
>>> +
>>> +		string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
>>> +		pr_warn("HugeTLB: %s %lu of page size %s failed. Only %s %lu hugepages.\n",
>>> +			count > old_max ? "increasing" : "decreasing",
>>> +			abs(count - old_max), buf,
>>> +			count > old_max ? "increased" : "decreased",
>>> +			abs(old_max - h->max_huge_pages));
>>> +	}
>>>  	spin_unlock(&hugetlb_lock);
>>
>> I would prefer if we drop the lock before logging the message.  That would
>> involve grabbing the value of h->max_huge_pages before dropping the lock.
> 
> Do you think the below change is OK to you to move the message logging
> after lock dropping? If yes, I will repost with updated patches.
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 6a9b7556ce5b..b5aa32a13569 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2661,7 +2661,7 @@ static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
>  static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
>  			      nodemask_t *nodes_allowed)
>  {
> -	unsigned long min_count, ret, old_max;
> +	unsigned long min_count, ret, old_max, new_max;
>  	NODEMASK_ALLOC(nodemask_t, node_alloc_noretry, GFP_KERNEL);
>  
>  	/*
> @@ -2780,7 +2780,10 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
>  	}
>  out:
>  	h->max_huge_pages = persistent_huge_pages(h);
> -	if (count != h->max_huge_pages) {
> +	new_max = h->max_huge_pages;
> +	spin_unlock(&hugetlb_lock);
> +
> +	if (count != new_max) {
>  		char buf[32];
>  
>  		string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
> @@ -2788,9 +2791,8 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
>  			count > old_max ? "increasing" : "decreasing",
>  			abs(count - old_max), buf,
>  			count > old_max ? "increased" : "decreased",
> -			abs(old_max - h->max_huge_pages));
> +			abs(old_max - new_max));
>  	}
> -	spin_unlock(&hugetlb_lock);
>  
>  	NODEMASK_FREE(node_alloc_noretry);

Yes, that looks better.  Thank you.

-- 
Mike Kravetz