linux-kernel - Re: [PATCH v2 2/3] mm, page_owner: decouple freeing stack trace from debug

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Date:   Tue, 1 Oct 2019 10:07:44 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Qian Cai <cai@....pw>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Walter Wu <walter-zh.wu@...iatek.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>
Subject: Re: [PATCH v2 2/3] mm, page_owner: decouple freeing stack trace from
 debug_pagealloc

On 10/1/19 1:49 AM, Qian Cai wrote:
> 
> 
>> On Sep 30, 2019, at 5:43 PM, Vlastimil Babka <vbabka@...e.cz> wrote:
>>
>> Well, my use case is shipping production kernels with CONFIG_PAGE_OWNER
>> and CONFIG_DEBUG_PAGEALLOC enabled, and instructing users to boot-time
>> enable only for troubleshooting a crash or memory leak, without a need
>> to install a debug kernel. Things like static keys and page_ext
>> allocations makes this possible without CPU and memory overhead when not
>> boot-time enabled. I don't know too much about KASAN internals, but I
>> assume it's not possible to use it that way on production kernels yet?
> 
> In that case, why can’t users just simply enable page_owner=on and debug_pagealloc=on for troubleshooting? The later makes the kernel slower, but I am not sure if it is worth optimization by adding a new parameter. There have already been quite a few MM-related kernel parameters that could tidy up a bit in the future.

They can do that and it was intention, yes. The extra parameter was
requested by Kirill, so I'll defer the answer to him :)