From: Mike Kravetz <mike.kravetz@oracle.com>
To: Nitesh Narayan Lal <nitesh@redhat.com>,
"Longpeng (Mike)" <longpeng2@huawei.com>
Cc: arei.gonglei@huawei.com, huangzhichao@huawei.com,
Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>, Qian Cai <cai@lca.pw>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] mm/hugetlb: avoid weird message in hugetlb_init
Date: Mon, 13 Apr 2020 11:33:24 -0700 [thread overview]
Message-ID: <f2bb2878-0584-6774-8e69-162a9ec68728@oracle.com> (raw)
In-Reply-To: <641eae15-1ea7-c573-0d64-09dcccc1717d@redhat.com>
On 4/10/20 8:47 AM, Nitesh Narayan Lal wrote:
> Hi Mike,
>
> On platforms that support multiple huge page sizes when 'hugepagesz' is not
> specified before 'hugepages=', hugepages are not allocated. (For example
> if we are requesting 1GB hugepages)
Hi Nitesh,
This should only be an issue with gigantic huge pages. This is because
hugepages=X not following a hugepagesz=Y specifies the number of huge pages
of default size to allocate. It does not currently work for gigantic pages.
In the other thread, I provided this explanation as to why:
It comes about because we do not definitively set the default huge page size
until after command line processing (in hugetlb_init). And, we must
preallocate gigantic huge pages during command line processing because that
is when the bootmem allocater is available.
I will be looking into modifying this behavior to allocate the pages as
expected, even for gigantic pages.
> In terms of reporting meminfo and /sys/kernel/../nr_hugepages reports the
> expected results but if we use sysctl vm.nr_hugepages then it reports a non-zero
> value as it reads the max_huge_pages from the default hstate instead of
> nr_huge_pages.
> AFAIK nr_huge_pages is the one that indicates the number of huge pages that are
> successfully allocated.
>
> Does vm.nr_hugepages is expected to report the maximum number of hugepages? If
> so, will it not make sense to rename the procname?
>
> However, if we expect nr_hugepages to report the number of successfully
> allocated hugepages then we should use nr_huge_pages in
> hugetlb_sysctl_handler_common().
This looks like a bug. Neither sysctl or the /proc file should be reporting
a non-zero value if huge pages do not exist.
--
Mike Kravetz
next prev parent reply other threads:[~2020-04-13 18:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-05 3:30 [PATCH] mm/hugetlb: avoid weird message in hugetlb_init Longpeng(Mike)
2020-03-06 0:09 ` Mike Kravetz
2020-03-06 6:36 ` Longpeng (Mike)
2020-03-06 20:12 ` Mike Kravetz
2020-03-09 8:16 ` Longpeng (Mike)
2020-04-10 15:47 ` Nitesh Narayan Lal
2020-04-13 18:33 ` Mike Kravetz [this message]
2020-04-13 21:21 ` Nitesh Narayan Lal
2020-04-15 4:03 ` Mike Kravetz
2020-04-15 11:46 ` Nitesh Narayan Lal
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