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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 14:09:06 +0100	[thread overview]
Message-ID: <20190104130906.GO31793@dhcp22.suse.cz> (raw)
In-Reply-To: <a5666d82-b7ad-4b90-5f4e-fd22afc3e1dc@lca.pw>

On Thu 03-01-19 17:22:29, Qian Cai wrote:
> On 1/3/19 3:22 PM, Michal Hocko wrote:
> > On Thu 03-01-19 14:53:47, Qian Cai wrote:
> >> On 1/3/19 2:07 PM, Michal Hocko wrote> So can we make the revert with an
> >> explanation that the patch was wrong?
> >>> If we want to make hacks to catch more objects to be tracked then it
> >>> would be great to have some numbers in hands.
> >>
> >> Well, those numbers are subject to change depends on future start_kernel()
> >> order. Right now, there are many functions could be caught earlier by page owner.
> >>
> >> 	kmemleak_init();
> > [...]
> >> 	sched_init_smp();
> > 
> > The kernel source dump will not tell us much of course. A ball park
> > number whether we are talking about dozen, hundreds or thousands of
> > allocations would tell us something at least, doesn't it.
> > 
> > Handwaving that it might help us some is not particurarly useful. We are
> > already losing some allocations already. Does it matter? Well, that
> > depends, sometimes we do want to catch an owner of particular page and
> > it is sad to find nothing. But how many times have you or somebody else
> > encountered that in practice. That is exactly a useful information to
> > judge an ugly ifdefery in the code. See my point?
> 
> 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_?

-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2019-01-04 13:09 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1545172285.18411.26.camel@lca.pw>
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
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 [this message]
2019-01-04 15:01                                 ` Qian Cai
2019-01-04 15:17                                   ` Michal Hocko
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 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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