Message-ID: <037227db-c869-7d9c-65e8-8f5f8682171d@suse.cz>
Date:   Tue, 16 Nov 2021 12:26:17 +0100
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Subject: Re: [PATCH v3] slob: add size header to all allocations
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To:     Rustam Kovhaev <rkovhaev@gmail.com>, cl@linux.com,
        penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com,
        akpm@linux-foundation.org, corbet@lwn.net
Cc:     djwong@kernel.org, david@fromorbit.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-doc@vger.kernel.org, gregkh@linuxfoundation.org,
        viro@zeniv.linux.org.uk, dvyukov@google.com
References: <be7ee3a6-9b3c-b436-f042-82bd3c416acc@suse.cz>
 <20211029030534.3847165-1-rkovhaev@gmail.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20211029030534.3847165-1-rkovhaev@gmail.com>
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On 10/29/21 05:05, Rustam Kovhaev wrote:
> Let's prepend both kmalloc() and kmem_cache_alloc() allocations with the
> size header.
> It simplifies the slab API and guarantees that both kmem_cache_alloc()
> and kmalloc() memory could be freed by kfree().
> 
> meminfo right after the system boot, x86-64 on xfs, without the patch:
> Slab:              35456 kB
> 
> the same, with the patch:
> Slab:              36100 kB
> 
> Link: https://lore.kernel.org/lkml/20210929212347.1139666-1-rkovhaev@gmail.com
> Signed-off-by: Rustam Kovhaev <rkovhaev@gmail.com>

Sorry for the late reply. I think we can further simplify this. We have:

static void *slob_alloc(size_t size, gfp_t gfp, int align,
			int node, int align_offset)

Previously there was one caller that passed size as unchanged, align_offset
= 0, the other passed size + SLOB_HDR_SIZE, align_offset = SLOB_HDR_SIZE.
Now both callers do the latter. We can drop the align_offset parameter and
pass size unchanged. slob_alloc() can internally add SLOB_HDR_SIZE to size,
and use SLOB_HDR_SIZE instead of align_offset.

Thanks,
Vlastimil