From: Vijay Balakrishna <vijayb@linux.microsoft.com>
To: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Oleg Nesterov <oleg@redhat.com>, Song Liu <songliubraving@fb.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Michal Hocko <mhocko@suse.com>, Allen Pais <apais@microsoft.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>
Subject: Re: [v1] mm: khugepaged: avoid overriding min_free_kbytes set by user
Date: Tue, 15 Sep 2020 12:31:56 -0700 [thread overview]
Message-ID: <db07095f-45d1-8e20-ccc7-0607e57ad91d@linux.microsoft.com> (raw)
In-Reply-To: <CA+CK2bDH-BGAWhCYLpsxwhS1+eHibqmjLiXAhyr0i94YJspYuA@mail.gmail.com>
On 9/15/2020 11:27 AM, Pavel Tatashin wrote:
> On Tue, Sep 15, 2020 at 12:55 AM Vijay Balakrishna
> <vijayb@linux.microsoft.com> wrote:
>>
>> set_recommended_min_free_kbytes need to honor min_free_kbytes set by the
>> user. Post start-of-day THP enable or memory hotplug operations can
>> lose user specified min_free_kbytes, in particular when it is higher than
>> calculated recommended value.
>>
>> Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
>> Cc: stable@vger.kernel.org
>> ---
>> mm/khugepaged.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
>> index 4f7107476a6f..b4b753ba411a 100644
>> --- a/mm/khugepaged.c
>> +++ b/mm/khugepaged.c
>> @@ -2253,7 +2253,7 @@ static void set_recommended_min_free_kbytes(void)
>> {
>> struct zone *zone;
>> int nr_zones = 0;
>> - unsigned long recommended_min;
>> + int recommended_min;
>
> Hi Vijay,
>
> Please explain in log the type change. user_min_free_kbytes is of
> "int" type and is initialized to -1, so comparing to unsigned leads to
> undesired effect.
Hi Pasha,
I will update log. I uncovered it when trying to understand why
one-line change to address issue raised by Kirill didn't work!
>
>
>>
>> for_each_populated_zone(zone) {
>> /*
>> @@ -2280,12 +2280,12 @@ static void set_recommended_min_free_kbytes(void)
>>
>> /* don't ever allow to reserve more than 5% of the lowmem */
>> recommended_min = min(recommended_min,
>> - (unsigned long) nr_free_buffer_pages() / 20);
>> + (int) nr_free_buffer_pages() / 20);
>> recommended_min <<= (PAGE_SHIFT-10);
>>
>> - if (recommended_min > min_free_kbytes) {
>> + if (recommended_min > user_min_free_kbytes) {
>
> Took me a while to understand, but this change is correct. It is the
> same logic that is done in init_per_zone_wmark_min().
>
> Please join the two patches you have in one patch series.
> Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Will do.
Thanks,
Vijay
>
> Thank you,
> Pasha
>
prev parent reply other threads:[~2020-09-15 19:33 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-15 4:55 [v1] mm: khugepaged: avoid overriding min_free_kbytes set by user Vijay Balakrishna
2020-09-15 18:27 ` Pavel Tatashin
2020-09-15 19:31 ` Vijay Balakrishna [this message]
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