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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id n3sm30066096qtc.81.2019.01.03.14.22.29 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 03 Jan 2019 14:22:30 -0800 (PST) Subject: Re: [PATCH v3] mm/page_owner: fix for deferred struct page init To: Michal Hocko 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 References: <20181220185031.43146-1-cai@lca.pw> <20181220203156.43441-1-cai@lca.pw> <20190103115114.GL31793@dhcp22.suse.cz> <20190103165927.GU31793@dhcp22.suse.cz> <5d8f3a98-a954-c8ab-83d9-2f94c614f268@lca.pw> <20190103190715.GZ31793@dhcp22.suse.cz> <62e96e34-7ea9-491a-b5b6-4828da980d48@lca.pw> <20190103202235.GE31793@dhcp22.suse.cz> From: Qian Cai Message-ID: Date: Thu, 3 Jan 2019 17:22:29 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 MIME-Version: 1.0 In-Reply-To: <20190103202235.GE31793@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.