From: Andrew Morton <akpm@linux-foundation.org>
To: Feng Tang <feng.tang@intel.com>
Cc: Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Vlastimil Babka <vbabka@suse.cz>,
Roman Gushchin <roman.gushchin@linux.dev>,
Hyeonggon Yoo <42.hyeyoo@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
dave.hansen@intel.com, Joerg Roedel <jroedel@suse.de>,
Robin Murphy <robin.murphy@arm.com>
Subject: Re: [RFC PATCH] mm/slub: enable debugging memory wasting of kmalloc
Date: Wed, 29 Jun 2022 19:30:06 -0700 [thread overview]
Message-ID: <20220629193006.77e9f071a5940e882c459cdd@linux-foundation.org> (raw)
In-Reply-To: <20220630014715.73330-1-feng.tang@intel.com>
On Thu, 30 Jun 2022 09:47:15 +0800 Feng Tang <feng.tang@intel.com> wrote:
> kmalloc's API family is critical for mm, with one shortcoming that
> its object size is fixed to be power of 2. When user requests memory
> for '2^n + 1' bytes, actually 2^(n+1) bytes will be allocated, so
> in worst case, there is around 50% memory space waste.
>
> We've met a kernel boot OOM panic, and from the dumped slab info:
>
> [ 26.062145] kmalloc-2k 814056KB 814056KB
>
> >From debug we found there are huge number of 'struct iova_magazine',
> whose size is 1032 bytes (1024 + 8), so each allocation will waste
> 1016 bytes. Though the issue is solved by giving the right(bigger)
> size of RAM, it is still better to optimize the size (either use
> a kmalloc friendly size or create a dedicated slab for it).
Well that's nice, and additional visibility is presumably a good thing.
But what the heck is going on with iova_magazine? Is anyone looking at
moderating its impact?
next prev parent reply other threads:[~2022-06-30 2:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-30 1:47 Feng Tang
2022-06-30 2:30 ` Andrew Morton [this message]
2022-06-30 2:38 ` Feng Tang
2022-06-30 2:47 ` Andrew Morton
2022-06-30 3:23 ` Feng Tang
2022-06-30 8:52 ` Robin Murphy
2022-06-30 14:38 ` Hyeonggon Yoo
2022-06-30 14:55 ` Hyeonggon Yoo
2022-07-01 2:23 ` Feng Tang
2022-07-01 9:29 ` Hyeonggon Yoo
2022-07-01 11:13 ` Feng Tang
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