Date: Fri, 24 Jul 2015 10:12:37 -0700
From: =?iso-8859-1?Q?J=F6rn?= Engel <joern@purestorage.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Spencer Baugh <sbaugh@catern.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        David Rientjes <rientjes@google.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Luiz Capitulino <lcapitulino@redhat.com>,
        "open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
        open list <linux-kernel@vger.kernel.org>,
        Spencer Baugh <Spencer.baugh@purestorage.com>,
        Joern Engel <joern@logfs.org>
Subject: Re: [PATCH] hugetlb: cond_resched for set_max_huge_pages and
 follow_hugetlb_page
Message-ID: <20150724171237.GC3458@Sligo.logfs.org>
References: <1437688476-3399-1-git-send-email-sbaugh@catern.com>
 <20150724065959.GB4622@dhcp22.suse.cz>
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On Fri, Jul 24, 2015 at 08:59:59AM +0200, Michal Hocko wrote:
> On Thu 23-07-15 14:54:31, Spencer Baugh wrote:
> > From: Joern Engel <joern@logfs.org>
> > 
> > ~150ms scheduler latency for both observed in the wild.
> 
> This is way to vague. Could you describe your problem somehow more,
> please?
> There are schduling points in the page allocator (when it triggers the
> reclaim), why are those not sufficient? Or do you manage to allocate
> many hugetlb pages without performing the reclaim and that leads to
> soft lockups?

We don't use transparent hugepages - they cause too much latency.
Instead we reserve somewhere around 3/4 or so of physical memory for
hugepages.  "sysctl -w vm.nr_hugepages=100000" or something similar in a
startup script.

Since it is early in boot we don't go through page reclaim.

J?rn

--
Everything should be made as simple as possible, but not simpler.
-- Albert Einstein
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