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From: Michal Hocko <mhocko@suse.com>
To: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
	mike.kravetz@Oracle.com, n-horiguchi@ah.jp.nec.com,
	aneesh.kumar@linux.vnet.ibm.com, gerald.schaefer@de.ibm.com,
	zhongjiang@huawei.com, aarcange@redhat.com,
	kirill.shutemov@linux.intel.com
Subject: Re: [PATCH] mm/hugetlb: Warn the user when issues arise on boot due to hugepages
Date: Tue, 6 Jun 2017 07:49:18 +0200	[thread overview]
Message-ID: <20170606054917.GA1189@dhcp22.suse.cz> (raw)
In-Reply-To: <20170605151541.avidrotxpoiekoy5@oracle.com>

On Mon 05-06-17 11:15:41, Liam R. Howlett wrote:
> * Michal Hocko <mhocko@suse.com> [170605 00:57]:
> > On Fri 02-06-17 20:54:13, Liam R. Howlett wrote:
> > > When the user specifies too many hugepages or an invalid
> > > default_hugepagesz the communication to the user is implicit in the
> > > allocation message.  This patch adds a warning when the desired page
> > > count is not allocated and prints an error when the default_hugepagesz
> > > is invalid on boot.
> > 
> > We do not warn when doing echo $NUM > nr_hugepages, so why should we
> > behave any different during the boot?
> 
> During boot hugepages will allocate until there is a fraction of the
> hugepage size left.  That is, we allocate until either the request is
> satisfied or memory for the pages is exhausted.  When memory for the
> pages is exhausted, it will most likely lead to the system failing with
> the OOM manager not finding enough (or anything) to kill (unless you're
> using really big hugepages in the order of 100s of MB or in the GBs).
> The user will most likely see the OOM messages much later in the boot
> sequence than the implicitly stated message.  Worse yet, you may even
> get an OOM for each processor which causes many pages of OOMs on modern
> systems.  Although these messages will be printed earlier than the OOM
> messages, at least giving the user errors and warnings will highlight
> the configuration as an issue.  I'm trying to point the user in the
> right direction by providing a more robust statement of what is failing.

Well, an oom report will tell us how much memory is eaten by hugetlb so
you would get a clue that something is misconfigured.
-- 
Michal Hocko
SUSE Labs

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  reply	other threads:[~2017-06-06  5:49 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-03  0:54 [PATCH] mm/hugetlb: Warn the user when issues arise on boot due to hugepages Liam R. Howlett
2017-06-05  4:57 ` Michal Hocko
2017-06-05 15:15   ` Liam R. Howlett
2017-06-06  5:49     ` Michal Hocko [this message]
2017-06-06  6:01       ` Michal Hocko
2017-06-12 17:28         ` Liam R. Howlett
2017-06-12 17:49           ` Michal Hocko
2017-06-12 18:37             ` Liam R. Howlett
2017-06-12 18:52               ` Michal Hocko
2017-06-13  1:35                 ` Liam R. Howlett
2017-06-13  5:42                   ` Michal Hocko
2017-06-13 15:25                     ` Liam R. Howlett
2017-06-13 16:26                       ` Mike Kravetz
2017-06-14  7:27                         ` Michal Hocko
2017-06-14 17:02                           ` Mike Kravetz
2017-06-14  7:25                       ` Michal Hocko
2017-06-16 19:07                   ` Andrew Morton
2017-06-17  0:25                     ` Mike Kravetz
2017-06-17  6:51                     ` Michal Hocko
2017-06-19 19:59                       ` Liam R. Howlett
2017-06-05 22:38 ` Andrew Morton
2017-06-06 19:03   ` Matthew Wilcox

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