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

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Message-ID: <cbbb78bd-4719-b9f4-ea5b-0b74675bfce7@suse.cz>
Date:   Tue, 1 Oct 2019 16:15:17 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Qian Cai <cai@....pw>, "Kirill A. Shutemov" <kirill@...temov.name>
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 3:18 PM, Qian Cai wrote:
> On Tue, 2019-10-01 at 14:35 +0200, Vlastimil Babka wrote:
>> On 10/1/19 2:32 PM, Vlastimil Babka wrote:
>>
>> Or suggest how to replace page_owner=on with something else (page_owner=full?)
>> and I can change that. But I don't want to implement a variant where we store only
>> the freeing stack, though.
> 
> I don't know why you think it is a variant. It sounds to me it is a natural
> extension that belongs to page_owner=on that it could always store freeing stack
> to help with debugging. Then, it could make implementation easier without all
> those different  combinations you mentioned in the patch description that could
> confuse anyone.
> 
> If someone complains about the overhead introduced to the existing page_owner=on
> users, then I think we should have some number to prove that say how much
> overhead there by storing freeing stack in page_owner=on, 10%, 50%?

I'll wait a few days for these overhead objections and if there are none I will
post a version that removes the parameter and stores freeing stack unconditionally.