[PATCH V2] mm/hugetlb: add is_resv_equal_free() func

[PATCH V2] mm/hugetlb: add is_resv_equal_free() func

[Xin Hao]

In hugetlb.c file, there are several places to compare the values of
'h->free_huge_pages' and 'h->resv_huge_pages', it looks a bit messy, so
there add a new is_resv_equal_free() func to do these.

Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
---
 mm/hugetlb.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 66496fc424f4..db6f63fb083f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1191,6 +1191,11 @@ static struct page *dequeue_huge_page_nodemask(struct hstate *h, gfp_t gfp_mask,
 	return NULL;
 }

+static inline bool is_resv_equal_free(struct hstate *h)
+{
+	return (h->free_huge_pages - h->resv_huge_pages == 0) ? true : false;
+}
+
 static struct page *dequeue_huge_page_vma(struct hstate *h,
 				struct vm_area_struct *vma,
 				unsigned long address, int avoid_reserve,
@@ -1207,12 +1212,11 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
 	 * have no page reserves. This check ensures that reservations are
 	 * not "stolen". The child may still get SIGKILLed
 	 */
-	if (!vma_has_reserves(vma, chg) &&
-			h->free_huge_pages - h->resv_huge_pages == 0)
+	if (!vma_has_reserves(vma, chg) && is_resv_equal_free(h))
 		goto err;

 	/* If reserves cannot be used, ensure enough pages are in the pool */
-	if (avoid_reserve && h->free_huge_pages - h->resv_huge_pages == 0)
+	if (avoid_reserve && is_resv_equal_free(h))
 		goto err;

 	gfp_mask = htlb_alloc_mask(h);
@@ -2105,7 +2109,7 @@ int dissolve_free_huge_page(struct page *page)
 	if (!page_count(page)) {
 		struct page *head = compound_head(page);
 		struct hstate *h = page_hstate(head);
-		if (h->free_huge_pages - h->resv_huge_pages == 0)
+		if (is_resv_equal_free(h))
 			goto out;

 		/*
@@ -2315,7 +2319,7 @@ struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
 		nodemask_t *nmask, gfp_t gfp_mask)
 {
 	spin_lock_irq(&hugetlb_lock);
-	if (h->free_huge_pages - h->resv_huge_pages > 0) {
+	if (!is_resv_equal_free(h)) {
 		struct page *page;

 		page = dequeue_huge_page_nodemask(h, gfp_mask, preferred_nid, nmask);
--
2.31.0

Re: [PATCH V2] mm/hugetlb: add is_resv_equal_free() func

[Andrew Morton]

On Fri, 16 Sep 2022 14:41:27 +0800 Xin Hao <xhao@linux.alibaba.com> wrote:

> In hugetlb.c file, there are several places to compare the values of
> 'h->free_huge_pages' and 'h->resv_huge_pages', it looks a bit messy, so
> there add a new is_resv_equal_free() func to do these.
> 
> ...
>
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1191,6 +1191,11 @@ static struct page *dequeue_huge_page_nodemask(struct hstate *h, gfp_t gfp_mask,
>  	return NULL;
>  }
> 
> +static inline bool is_resv_equal_free(struct hstate *h)

I'm not sure that's a well chosen name.  A better name would reflect
the *meaning* of free_huge_pages being equal to resv_huge_pages.  Maybe
something like reserves_exhausted()?

This would all be clearer if we'd bothered to document the fields of
struct hstate :(


> +{
> +	return (h->free_huge_pages - h->resv_huge_pages == 0) ? true : false;

	return h->free_huge_pages == h->resv_huge_pages;

> +}

Re: [PATCH V2] mm/hugetlb: add is_resv_equal_free() func

[Mike Kravetz]

On 09/16/22 13:12, Andrew Morton wrote:
> On Fri, 16 Sep 2022 14:41:27 +0800 Xin Hao <xhao@linux.alibaba.com> wrote:
> 
> > In hugetlb.c file, there are several places to compare the values of
> > 'h->free_huge_pages' and 'h->resv_huge_pages', it looks a bit messy, so
> > there add a new is_resv_equal_free() func to do these.
> > 
> > ...
> >
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -1191,6 +1191,11 @@ static struct page *dequeue_huge_page_nodemask(struct hstate *h, gfp_t gfp_mask,
> >  	return NULL;
> >  }
> > 
> > +static inline bool is_resv_equal_free(struct hstate *h)
> 
> I'm not sure that's a well chosen name.  A better name would reflect
> the *meaning* of free_huge_pages being equal to resv_huge_pages.  Maybe
> something like reserves_exhausted()?

How about calling it free_non_reserved_huge_pages() and returning the actual
value (h->free_huge_pages - h->resv_huge_pages)?

Perhaps available_huge_pages()?

It could then be used in at least one other place
- if (h->free_huge_pages - h->resv_huge_pages > 0)

> This would all be clearer if we'd bothered to document the fields of
> struct hstate :(

Agree, and discussed elsewhwere some may even be able to be eliminated.  I can
add that to my todo list.
-- 
Mike Kravetz

> 
> 
> > +{
> > +	return (h->free_huge_pages - h->resv_huge_pages == 0) ? true : false;
> 
> 	return h->free_huge_pages == h->resv_huge_pages;
> 
> > +}
> 

Re: [PATCH V2] mm/hugetlb: add is_resv_equal_free() func

[haoxin]

在 2022/9/17 上午5:09, Mike Kravetz 写道:
> On 09/16/22 13:12, Andrew Morton wrote:
>> On Fri, 16 Sep 2022 14:41:27 +0800 Xin Hao <xhao@linux.alibaba.com> wrote:
>>
>>> In hugetlb.c file, there are several places to compare the values of
>>> 'h->free_huge_pages' and 'h->resv_huge_pages', it looks a bit messy, so
>>> there add a new is_resv_equal_free() func to do these.
>>>
>>> ...
>>>
>>> --- a/mm/hugetlb.c
>>> +++ b/mm/hugetlb.c
>>> @@ -1191,6 +1191,11 @@ static struct page *dequeue_huge_page_nodemask(struct hstate *h, gfp_t gfp_mask,
>>>   	return NULL;
>>>   }
>>>
>>> +static inline bool is_resv_equal_free(struct hstate *h)
>> I'm not sure that's a well chosen name.  A better name would reflect
>> the *meaning* of free_huge_pages being equal to resv_huge_pages.  Maybe
>> something like reserves_exhausted()?
> How about calling it free_non_reserved_huge_pages() and returning the actual
> value (h->free_huge_pages - h->resv_huge_pages)?
>
> Perhaps available_huge_pages()?
Ok, I am going to use available_huge_pages() in the patch v3, thanks.
> It could then be used in at least one other place
> - if (h->free_huge_pages - h->resv_huge_pages > 0)
>
>> This would all be clearer if we'd bothered to document the fields of
>> struct hstate :(
> Agree, and discussed elsewhwere some may even be able to be eliminated.  I can
> add that to my todo list.