From: Michal Hocko <mhocko@kernel.org>
To: Qian Cai <cai@lca.pw>
Cc: akpm@linux-foundation.org, Pavel.Tatashin@microsoft.com,
mingo@kernel.org, mgorman@techsingularity.net,
iamjoonsoo.kim@lge.com, tglx@linutronix.de, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] mm/page_owner: fix for deferred struct page init
Date: Fri, 4 Jan 2019 16:17:37 +0100 [thread overview]
Message-ID: <20190104151737.GT31793@dhcp22.suse.cz> (raw)
In-Reply-To: <e4ad9d12-387d-1cc6-f404-cae6d43ccf80@lca.pw>
On Fri 04-01-19 10:01:40, Qian Cai wrote:
> On 1/4/19 8:09 AM, Michal Hocko wrote:
> >> Here is the number without DEFERRED_STRUCT_PAGE_INIT.
> >>
> >> == page_ext_init() after page_alloc_init_late() ==
> >> Node 0, zone DMA: page owner found early allocated 0 pages
> >> Node 0, zone DMA32: page owner found early allocated 7009 pages
> >> Node 0, zone Normal: page owner found early allocated 85827 pages
> >> Node 4, zone Normal: page owner found early allocated 75063 pages
> >>
> >> == page_ext_init() before kmemleak_init() ==
> >> Node 0, zone DMA: page owner found early allocated 0 pages
> >> Node 0, zone DMA32: page owner found early allocated 6654 pages
> >> Node 0, zone Normal: page owner found early allocated 41907 pages
> >> Node 4, zone Normal: page owner found early allocated 41356 pages
> >>
> >> So, it told us that it will miss tens of thousands of early page allocation call
> >> sites.
> >
> > This is an answer for the first part of the question (how much). The
> > second is _do_we_care_?
>
> Well, the purpose of this simple "ugly" ifdef is to avoid a regression for the
> existing page_owner users with DEFERRED_STRUCT_PAGE_INIT deselected that would
> start to miss tens of thousands early page allocation call sites.
I am pretty sure we will hear about that when that happens. And act
accordingly.
> The other option I can think of to not hurt your eyes is to rewrite the whole
> page_ext_init(), init_page_owner(), init_debug_guardpage() to use all early
> functions, so it can work in both with DEFERRED_STRUCT_PAGE_INIT=y and without.
> However, I have a hard-time to convince myself it is a sensible thing to do.
Or simply make the page_owner initialization only touch the already
initialized memory. Have you explored that option as well?
Look, I am trying to push for a clean solution. Hacks I have seen so
far are not convincing. You have identified a regression and as such I
would consider the most straightforward to revert the buggy commit. If
you want to improve the situation then I would suggest to think about
something that is more robust than ifdefed hacks. It might be more work
but it also might be a better thing long term.
If you think I am asking too much then you are free to ignore my
opinion. I am not a maintainer of the page_owner code.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-01-04 15:17 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-18 22:31 kernel panic with page_owner=on Qian Cai
2018-12-19 1:57 ` [PATCH] mm: skip checking poison pattern for page_to_nid() Qian Cai
2018-12-19 10:20 ` Michal Hocko
2018-12-19 12:46 ` Qian Cai
2018-12-20 6:03 ` [PATCH] mm/page_owner: fix for deferred struct page init Qian Cai
2018-12-20 9:22 ` Michal Hocko
2018-12-20 18:50 ` [PATCH v2] " Qian Cai
2018-12-20 20:31 ` [PATCH v3] " Qian Cai
2018-12-20 21:00 ` William Kucharski
2018-12-20 21:04 ` Qian Cai
2018-12-20 21:04 ` Qian Cai
2019-01-03 11:51 ` Michal Hocko
2019-01-03 16:38 ` Qian Cai
2019-01-03 16:59 ` Michal Hocko
2019-01-03 17:38 ` Qian Cai
2019-01-03 19:07 ` Michal Hocko
2019-01-03 19:53 ` Qian Cai
2019-01-03 20:22 ` Michal Hocko
2019-01-03 22:22 ` Qian Cai
2019-01-04 13:09 ` Michal Hocko
2019-01-04 15:01 ` Qian Cai
2019-01-04 15:17 ` Michal Hocko [this message]
2019-01-04 15:25 ` Qian Cai
2019-01-04 15:32 ` Michal Hocko
2019-01-04 20:18 ` Qian Cai
2019-01-07 18:43 ` Michal Hocko
2019-01-08 1:53 ` Qian Cai
2019-01-08 8:20 ` Michal Hocko
2019-01-08 13:19 ` Qian Cai
2019-01-08 13:19 ` Qian Cai
2019-01-08 22:02 ` Andrew Morton
2019-01-08 22:13 ` Qian Cai
2019-01-08 22:40 ` Michal Hocko
2019-01-09 7:34 ` [PATCH v2] " Michal Hocko
2019-01-15 20:28 ` [PATCH] Revert "mm: use early_pfn_to_nid in page_ext_init" Qian Cai
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