linux-kernel - Re: [RESEND PATCH v7 10/10] selftests/mm/cow: Add tests for anonymous small-sized THP

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Message-ID: <13a2ce75-b1c0-4930-8911-36ded0b428a7@redhat.com>
Date:   Mon, 27 Nov 2023 15:50:46 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Ryan Roberts <ryan.roberts@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Yin Fengwei <fengwei.yin@...el.com>,
        Yu Zhao <yuzhao@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Yang Shi <shy828301@...il.com>,
        "Huang, Ying" <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Itaru Kitayama <itaru.kitayama@...il.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        John Hubbard <jhubbard@...dia.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Hugh Dickins <hughd@...gle.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     linux-mm@...ck.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v7 10/10] selftests/mm/cow: Add tests for anonymous
 small-sized THP

On 27.11.23 15:02, Ryan Roberts wrote:
> On 22/11/2023 16:29, Ryan Roberts wrote:
>> Add tests similar to the existing PMD-sized THP tests, but which operate
>> on memory backed by (PTE-mapped) small-sized THP. This reuses all the
>> existing infrastructure. If the test suite detects that small-sized THP
>> is not supported by the kernel, the new tests are skipped.
>>
>> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
>> ---
>>   tools/testing/selftests/mm/cow.c | 71 +++++++++++++++++++++++++++++++-
>>   1 file changed, 70 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
>> index d03c453cfd5c..3efc395c7077 100644
>> --- a/tools/testing/selftests/mm/cow.c
>> +++ b/tools/testing/selftests/mm/cow.c
>> @@ -29,15 +29,49 @@
>>   #include "../../../../mm/gup_test.h"
>>   #include "../kselftest.h"
>>   #include "vm_util.h"
>> +#include "thp_settings.h"
>>
>>   static size_t pagesize;
>>   static int pagemap_fd;
>>   static size_t pmdsize;
>> +static int nr_thpsmallsizes;
>> +static size_t thpsmallsizes[20];
> 
> Off the back of some comments David made againt the previous patch [1], I'm
> proposing to rework this a bit so that ALL thp sizes are stored in this array,
> not just the non-PMD-sized sizes. This makes the changes overall a bit smaller
> and easier to understand, I think...
> 
>>   static int nr_hugetlbsizes;
>>   static size_t hugetlbsizes[10];
>>   static int gup_fd;
>>   static bool has_huge_zeropage;
>>
>> +static int sz2ord(size_t size)
>> +{
>> +	return __builtin_ctzll(size / pagesize);
>> +}
>> +
>> +static int detect_smallthp_sizes(size_t sizes[], int max)
> 
> This changes to detect_thp_sizes() and deposits all sizes in sizes[]

Just what I wanted to propose :) Makes it simpler by removing the 
"small" terminology and just detecting thp sizes.

-- 
Cheers,

David / dhildenb