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Subject: Re: [PATCH] xfs: use kmem_cache_free() for kmem_cache objects
To:     Rustam Kovhaev <rkovhaev@gmail.com>
Cc:     Dave Chinner <david@fromorbit.com>, djwong@kernel.org,
        linux-xfs@vger.kernel.org, cl@linux.com, penberg@kernel.org,
        rientjes@google.com, iamjoonsoo.kim@lge.com,
        akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, gregkh@linuxfoundation.org,
        Al Viro <viro@zeniv.linux.org.uk>
References: <20210929212347.1139666-1-rkovhaev@gmail.com>
 <20210930044202.GP2361455@dread.disaster.area>
 <17f537b3-e2eb-5d0a-1465-20f3d3c960e2@suse.cz> <YVYGcLbu/aDKXkag@nuc10>
From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <a9b3cd91-8ee6-a654-b2a8-00c3efb69559@suse.cz>
Date:   Thu, 30 Sep 2021 23:10:10 +0200
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On 9/30/21 8:48 PM, Rustam Kovhaev wrote:
> On Thu, Sep 30, 2021 at 10:13:40AM +0200, Vlastimil Babka wrote:
>>
>> I think it's fair if something like XFS (not meant for tiny systems AFAIK?)
>> excludes SLOB (meant for tiny systems). Clearly nobody tried to use these
>> two together last 5 years anyway.
> 
> +1 for adding Kconfig option, it seems like some things are not meant to
> be together.

But if we patch SLOB, we won't need it.

>> Maybe we could also just add the 4 bytes to all SLOB objects, declare
>> kfree() is always fine and be done with it. Yes, it will make SLOB footprint
>> somewhat less tiny, but even whan we added kmalloc power of two alignment
>> guarantees, the impact on SLOB was negligible.
> 
> I'll send a patch to add a 4-byte header for kmem_cache_alloc()
> allocations.

Thanks. Please report in the changelog slab usage from /proc/meminfo
before and after patch (at least a snapshot after a full boot).

>>> Thoughts?
>>>
>>> Cheers,
>>>
>>> Dave.
>>>
>>