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From: Michal Hocko <mhocko@kernel.org>
To: Juergen Gross <jgross@suse.com>
Cc: linux-mm@kvack.org,
	Alexander Duyck <alexander.h.duyck@linux.intel.com>,
	linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] [PATCH] mm: fix regression with deferred struct page init
Date: Fri, 28 Jun 2019 20:47:29 +0200	[thread overview]
Message-ID: <20190628184729.GJ2751@dhcp22.suse.cz> (raw)
In-Reply-To: <52a8e6d9-003e-c802-b8ff-327a8c7913a5@suse.com>

On Fri 28-06-19 19:38:13, Juergen Gross wrote:
> On 28.06.19 17:17, Michal Hocko wrote:
> > On Thu 20-06-19 18:08:21, Juergen Gross wrote:
> > > Commit 0e56acae4b4dd4a9 ("mm: initialize MAX_ORDER_NR_PAGES at a time
> > > instead of doing larger sections") is causing a regression on some
> > > systems when the kernel is booted as Xen dom0.
> > > 
> > > The system will just hang in early boot.
> > > 
> > > Reason is an endless loop in get_page_from_freelist() in case the first
> > > zone looked at has no free memory. deferred_grow_zone() is always
> > 
> > Could you explain how we ended up with the zone having no memory? Is
> > xen "stealing" memblock memory without adding it to memory.reserved?
> > In other words, how do we end up with an empty zone that has non zero
> > end_pfn?
> 
> Why do you think Xen is stealing the memory in an odd way?
> 
> Doesn't deferred_init_mem_pfn_range_in_zone() return false when no free
> memory is found? So exactly if the memory was added to memory.reserved
> that will happen.

You are right. I managed to confuse myself and thought that __next_mem_range
return index to both memblock types. But I am wrong here and it excludes
type_b regions. I should have read the documentation. My bad and sorry
for the confusion.
-- 
Michal Hocko
SUSE Labs

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Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org>
To: Juergen Gross <jgross@suse.com>
Cc: linux-mm@kvack.org,
	Alexander Duyck <alexander.h.duyck@linux.intel.com>,
	xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: fix regression with deferred struct page init
Date: Fri, 28 Jun 2019 20:47:29 +0200	[thread overview]
Message-ID: <20190628184729.GJ2751@dhcp22.suse.cz> (raw)
In-Reply-To: <52a8e6d9-003e-c802-b8ff-327a8c7913a5@suse.com>

On Fri 28-06-19 19:38:13, Juergen Gross wrote:
> On 28.06.19 17:17, Michal Hocko wrote:
> > On Thu 20-06-19 18:08:21, Juergen Gross wrote:
> > > Commit 0e56acae4b4dd4a9 ("mm: initialize MAX_ORDER_NR_PAGES at a time
> > > instead of doing larger sections") is causing a regression on some
> > > systems when the kernel is booted as Xen dom0.
> > > 
> > > The system will just hang in early boot.
> > > 
> > > Reason is an endless loop in get_page_from_freelist() in case the first
> > > zone looked at has no free memory. deferred_grow_zone() is always
> > 
> > Could you explain how we ended up with the zone having no memory? Is
> > xen "stealing" memblock memory without adding it to memory.reserved?
> > In other words, how do we end up with an empty zone that has non zero
> > end_pfn?
> 
> Why do you think Xen is stealing the memory in an odd way?
> 
> Doesn't deferred_init_mem_pfn_range_in_zone() return false when no free
> memory is found? So exactly if the memory was added to memory.reserved
> that will happen.

You are right. I managed to confuse myself and thought that __next_mem_range
return index to both memblock types. But I am wrong here and it excludes
type_b regions. I should have read the documentation. My bad and sorry
for the confusion.
-- 
Michal Hocko
SUSE Labs


  reply	other threads:[~2019-06-28 18:47 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-20 16:08 [Xen-devel] [PATCH] mm: fix regression with deferred struct page init Juergen Gross
2019-06-20 16:08 ` Juergen Gross
2019-06-20 16:10 ` [Xen-devel] " Alexander Duyck
2019-06-20 16:10   ` Alexander Duyck
2019-06-25  8:25 ` [Xen-devel] " Juergen Gross
2019-06-25  8:25   ` Juergen Gross
2019-06-27 15:35   ` [Xen-devel] " Juergen Gross
2019-06-27 15:35     ` Juergen Gross
2019-06-28 15:17 ` Michal Hocko
2019-06-28 15:17   ` Michal Hocko
2019-06-28 17:38   ` [Xen-devel] " Juergen Gross
2019-06-28 17:38     ` Juergen Gross
2019-06-28 18:47     ` Michal Hocko [this message]
2019-06-28 18:47       ` Michal Hocko

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