linux-kernel - Re: [PATCH] xfs: use kmem_cache_free() for kmem

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Message-ID: <a9b3cd91-8ee6-a654-b2a8-00c3efb69559@suse.cz>
Date:   Thu, 30 Sep 2021 23:10:10 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Rustam Kovhaev <rkovhaev@...il.com>
Cc:     Dave Chinner <david@...morbit.com>, djwong@...nel.org,
        linux-xfs@...r.kernel.org, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, gregkh@...uxfoundation.org,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] xfs: use kmem_cache_free() for kmem_cache objects

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.
>>>
>>