From: Bharata B Rao <bharata@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
pasha.tatashin@oracle.com
Subject: Re: Memory hotplug not increasing the total RAM
Date: Tue, 30 Jan 2018 15:23:45 +0530 [thread overview]
Message-ID: <20180130095345.GC1245@in.ibm.com> (raw)
In-Reply-To: <20180130092815.GR21609@dhcp22.suse.cz>
On Tue, Jan 30, 2018 at 10:28:15AM +0100, Michal Hocko wrote:
> On Tue 30-01-18 10:16:00, Michal Hocko wrote:
> > On Tue 30-01-18 14:00:06, Bharata B Rao wrote:
> > > Hi,
> > >
> > > With the latest upstream, I see that memory hotplug is not working
> > > as expected. The hotplugged memory isn't seen to increase the total
> > > RAM pages. This has been observed with both x86 and Power guests.
> > >
> > > 1. Memory hotplug code intially marks pages as PageReserved via
> > > __add_section().
> > > 2. Later the struct page gets cleared in __init_single_page().
> > > 3. Next online_pages_range() increments totalram_pages only when
> > > PageReserved is set.
> >
> > You are right. I have completely forgot about this late struct page
> > initialization during onlining. memory hotplug really doesn't want
> > zeroying. Let me think about a fix.
>
> Could you test with the following please? Not an act of beauty but
> we are initializing memmap in sparse_add_one_section for memory
> hotplug. I hate how this is different from the initialization case
> but there is quite a long route to unify those two... So a quick
> fix should be as follows.
Tested on Power guest, fixes the issue. I can now see the total memory
size increasing after hotplug.
Regards,
Bharata.
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WARNING: multiple messages have this Message-ID (diff)
From: Bharata B Rao <bharata@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
pasha.tatashin@oracle.com
Subject: Re: Memory hotplug not increasing the total RAM
Date: Tue, 30 Jan 2018 15:23:45 +0530 [thread overview]
Message-ID: <20180130095345.GC1245@in.ibm.com> (raw)
In-Reply-To: <20180130092815.GR21609@dhcp22.suse.cz>
On Tue, Jan 30, 2018 at 10:28:15AM +0100, Michal Hocko wrote:
> On Tue 30-01-18 10:16:00, Michal Hocko wrote:
> > On Tue 30-01-18 14:00:06, Bharata B Rao wrote:
> > > Hi,
> > >
> > > With the latest upstream, I see that memory hotplug is not working
> > > as expected. The hotplugged memory isn't seen to increase the total
> > > RAM pages. This has been observed with both x86 and Power guests.
> > >
> > > 1. Memory hotplug code intially marks pages as PageReserved via
> > > __add_section().
> > > 2. Later the struct page gets cleared in __init_single_page().
> > > 3. Next online_pages_range() increments totalram_pages only when
> > > PageReserved is set.
> >
> > You are right. I have completely forgot about this late struct page
> > initialization during onlining. memory hotplug really doesn't want
> > zeroying. Let me think about a fix.
>
> Could you test with the following please? Not an act of beauty but
> we are initializing memmap in sparse_add_one_section for memory
> hotplug. I hate how this is different from the initialization case
> but there is quite a long route to unify those two... So a quick
> fix should be as follows.
Tested on Power guest, fixes the issue. I can now see the total memory
size increasing after hotplug.
Regards,
Bharata.
next prev parent reply other threads:[~2018-01-30 9:53 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-30 8:30 Memory hotplug not increasing the total RAM Bharata B Rao
2018-01-30 8:30 ` Bharata B Rao
2018-01-30 9:16 ` Michal Hocko
2018-01-30 9:16 ` Michal Hocko
2018-01-30 9:28 ` Michal Hocko
2018-01-30 9:28 ` Michal Hocko
2018-01-30 9:53 ` Bharata B Rao [this message]
2018-01-30 9:53 ` Bharata B Rao
2018-01-30 10:11 ` Michal Hocko
2018-01-30 10:11 ` Michal Hocko
2018-01-30 18:11 ` Pavel Tatashin
2018-01-30 18:11 ` Pavel Tatashin
2018-01-30 18:29 ` Michal Hocko
2018-01-30 18:29 ` Michal Hocko
2018-01-30 19:12 ` Pavel Tatashin
2018-01-30 19:12 ` Pavel Tatashin
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