From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Baoquan He <bhe@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
mike.kravetz@oracle.com, david@redhat.com,
akpm@linux-foundation.org
Subject: Re: [PATCH v2 2/4] mm/hugetlb.c: Remove the unnecessary non_swap_entry()
Date: Thu, 23 Jul 2020 14:22:58 +0530 [thread overview]
Message-ID: <7c0d19e9-4f90-9f74-d364-4d877ccf67f9@arm.com> (raw)
In-Reply-To: <20200723061437.GQ32539@MiWiFi-R3L-srv>
On 07/23/2020 11:44 AM, Baoquan He wrote:
> On 07/23/20 at 10:36am, Anshuman Khandual wrote:
>>
>>
>> On 07/23/2020 08:52 AM, Baoquan He wrote:
>>> The checking is_migration_entry() and is_hwpoison_entry() are stricter
>>> than non_swap_entry(), means they have covered the conditional check
>>> which non_swap_entry() is doing.
>>
>> They are no stricter as such but implicitly contains non_swap_entry() in itself.
>> If a swap entry tests positive for either is_[migration|hwpoison]_entry(), then
>> its swap_type() is among SWP_MIGRATION_READ, SWP_MIGRATION_WRITE and SWP_HWPOISON.
>> All these types >= MAX_SWAPFILES, exactly what is asserted with non_swap_entry().
>>
>>>
>>> Hence remove the unnecessary non_swap_entry() in is_hugetlb_entry_migration()
>>> and is_hugetlb_entry_hwpoisoned() to simplify code.
>>>
>>> Signed-off-by: Baoquan He <bhe@redhat.com>
>>> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
>>> Reviewed-by: David Hildenbrand <david@redhat.com>
>>> ---
>>> mm/hugetlb.c | 4 ++--
>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>>> index 3569e731e66b..c14837854392 100644
>>> --- a/mm/hugetlb.c
>>> +++ b/mm/hugetlb.c
>>> @@ -3748,7 +3748,7 @@ bool is_hugetlb_entry_migration(pte_t pte)
>>> if (huge_pte_none(pte) || pte_present(pte))
>>> return false;
>>> swp = pte_to_swp_entry(pte);
>>> - if (non_swap_entry(swp) && is_migration_entry(swp))
>>> + if (is_migration_entry(swp))
>>> return true;
>>> else
>>> return false;
>>> @@ -3761,7 +3761,7 @@ static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
>>> if (huge_pte_none(pte) || pte_present(pte))
>>> return false;
>>> swp = pte_to_swp_entry(pte);
>>> - if (non_swap_entry(swp) && is_hwpoison_entry(swp))
>>> + if (is_hwpoison_entry(swp))
>>> return true;
>>> else
>>> return false;
>>>
>>
>> It would be better if the commit message contains details about
>> the existing redundant check. But either way.
>
> Thanks for your advice. Do you think updating the log as below is OK?
>
> ~~~~~~~~
> If a swap entry tests positive for either is_[migration|hwpoison]_entry(), then
> its swap_type() is among SWP_MIGRATION_READ, SWP_MIGRATION_WRITE and SWP_HWPOISON.
> All these types >= MAX_SWAPFILES, exactly what is asserted with non_swap_entry().
>
> So the checking non_swap_entry() in is_hugetlb_entry_migration() and
> is_hugetlb_entry_hwpoisoned() is redundant.
>
> Let's remove it to optimize code.
> ~~~~~~~~
Something like above would be good.
next prev parent reply other threads:[~2020-07-23 8:53 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-23 3:22 [PATCH v2 0/4] mm/hugetlb: Small cleanup and improvement Baoquan He
2020-07-23 3:22 ` [PATCH v2 1/4] mm/hugetlb.c: make is_hugetlb_entry_hwpoisoned return bool Baoquan He
2020-07-23 4:46 ` Anshuman Khandual
2020-07-23 3:22 ` [PATCH v2 2/4] mm/hugetlb.c: Remove the unnecessary non_swap_entry() Baoquan He
2020-07-23 5:06 ` Anshuman Khandual
2020-07-23 6:14 ` Baoquan He
2020-07-23 8:52 ` Anshuman Khandual [this message]
2020-07-23 10:46 ` [PATCH v3 " Baoquan He
2020-07-23 3:22 ` [PATCH v2 3/4] doc/vm: fix typo in the hugetlb admin documentation Baoquan He
2020-07-23 5:17 ` Anshuman Khandual
2020-07-23 5:57 ` Baoquan He
2020-07-23 3:22 ` [PATCH v2 4/4] mm/hugetl.c: warn out if expected count of huge pages adjustment is not achieved Baoquan He
2020-07-23 6:16 ` Anshuman Khandual
2020-07-23 9:11 ` Baoquan He
2020-07-23 18:21 ` Mike Kravetz
2020-07-24 14:59 ` Baoquan He
2020-08-11 2:11 ` Baoquan He
2020-08-11 3:35 ` Mike Kravetz
2020-08-11 7:24 ` Michal Hocko
2020-08-11 23:11 ` Mike Kravetz
2020-08-24 21:57 ` [PATCH v2 0/4] mm/hugetlb: Small cleanup and improvement Mike Kravetz
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