linux-kernel - Re: [PATCH] mm/page_owner: print largest memory consumer when OOM panic occurs

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Date:   Wed, 25 Dec 2019 08:53:12 -0500
From:   Qian Cai <cai@....pw>
To:     Miles Chen <miles.chen@...iatek.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-mediatek@...ts.infradead.org,
        wsd_upstream@...iatek.com
Subject: Re: [PATCH] mm/page_owner: print largest memory consumer when OOM panic occurs

> On Dec 25, 2019, at 4:29 AM, Miles Chen <miles.chen@...iatek.com> wrote:
> 
> For example, we're implementing our iommu driver and there are many
> alloc_pages() in drivers/iommu.
> This approach helps us located some memory leakages in our
> implementation.

Not sure if you have code that can share but I can’t imagine there are many places that would have a single call site in the driver doing alloc_pages() over and over again. For example, there is only two alloc_pages() in intel-iommu.c with one is only in the cold path, so even if alloc_pgtable_page() one do leaking, it is still up to there air if your patch will catch it because it may not a single call site and it needs to leak significant amount of memory to be the greatest consumer where it is just not so realistic. For debugging point of view, IMO it is better to annotate this one alloc_pages() call when in doubt, so that kmemleak would catch it instead.