linux-kernel - Re: [PATCH v6 1/4] mm/slub: enable debugging memory wasting of kmalloc

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Date:   Mon, 31 Oct 2022 19:42:41 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     John Thomson <lists@...nthomson.fastmail.com.au>
CC:     Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Andrey Konovalov <andreyknvl@...il.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
        Robin Murphy <robin.murphy@....com>,
        John Garry <john.garry@...wei.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>
Subject: Re: [PATCH v6 1/4] mm/slub: enable debugging memory wasting of
 kmalloc

On Mon, Oct 31, 2022 at 10:05:58AM +0000, John Thomson wrote:
> On Mon, 31 Oct 2022, at 02:36, Feng Tang wrote:
> >> > 
> >> > possibly relevant config options:
> >> > grep -E '(SLUB|SLAB)' .config
> >> > # SLAB allocator options
> >> > # CONFIG_SLAB is not set
> >> > CONFIG_SLUB=y
> >> > CONFIG_SLAB_MERGE_DEFAULT=y
> >> > # CONFIG_SLAB_FREELIST_RANDOM is not set
> >> > # CONFIG_SLAB_FREELIST_HARDENED is not set
> >> > # CONFIG_SLUB_STATS is not set
> >> > CONFIG_SLUB_CPU_PARTIAL=y
> >> > # end of SLAB allocator options
> >> > # CONFIG_SLUB_DEBUG is not set
> >> 
> >> Also not having CONFIG_SLUB_DEBUG enabled means most of the code the 
> >> patch/commit touches is not even active.
> >> Could this be some miscompile or code layout change exposing some 
> >> different bug, hmm.
> 
> Yes, it could be.
> 
> >> Is it any different if you do enable CONFIG_SLUB_DEBUG ?
> 
> No change
> 
> >> Or change to CONFIG_SLAB? (that would be really weird if not)
> 
> This boots fine
> 
> > I haven't found any clue from the code either, and I compiled
> > kernel with the config above and tested booting on an Alder-lake
> > desktop and a QEMU, which boot fine.
> >
> > Could you provide the full kernel config and demsg (in compressed
> > format if you think it's too big), so we can check more?
> 
> Attached
> 
> > Thanks,
> > Feng
> 
> vmlinux is bigger, and entry point is larger (0x8074081c vs 0x807407dc revert vs 0x8073fcbc),
> so that may be it? Or not?
> revert + SLUB_DEBUG + SLUB_DEBUG_ON is bigger still, but does successfully boot.
> vmlinux entry point is 0x8074705c

Thanks for prompt info!

As I can't reproduce it locally yet, could you help try 3 tests separately:
* change the O2/O3 compile option to O1
* try the attached 0001 patch (which cut part of commit)
* try attached 0001+0002 patch

Thanks!


- Feng




View attachment "0001-reduced-slub-patch.patch" of type "text/x-diff" (10900 bytes)

View attachment "0002-reorder-the-partial_context-initialization.patch" of type "text/x-diff" (1003 bytes)