linux-kernel - Re: [PATCH v2] mm/slab_common: Support the slub_debug boot option on specific object size

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Date:	Thu, 23 Apr 2015 19:15:41 +0800
From:	Gavin Guo <gavin.guo@...onical.com>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Christoph Lameter <cl@...ux.com>, penberg@...nel.org,
	rientjes@...gle.com, iamjoonsoo.kim@....com,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] mm/slab_common: Support the slub_debug boot option on
 specific object size

Hi Rasmus,

On Thu, Apr 23, 2015 at 5:55 PM, Rasmus Villemoes
<linux@...musvillemoes.dk> wrote:
> On Wed, Apr 22 2015, Gavin Guo <gavin.guo@...onical.com> wrote:
>
>>       /*
>> +      * The kmalloc_names is for temporary usage to make
>> +      * slub_debug=,kmalloc-xx option work in the boot time. The
>> +      * kmalloc_index() support to 2^26=64MB. So, the final entry of the
>> +      * table is kmalloc-67108864.
>> +      */
>> +     static const char *kmalloc_names[] = {
>
> The array itself could be const, but more importantly it should be
> marked __initconst so that the 27*sizeof(char*) bytes can be released after init.
>
>> +             "0",                    "kmalloc-96",           "kmalloc-192",
>> +             "kmalloc-8",            "kmalloc-16",           "kmalloc-32",
>> +             "kmalloc-64",           "kmalloc-128",          "kmalloc-256",
>> +             "kmalloc-512",          "kmalloc-1024",         "kmalloc-2048",
>> +             "kmalloc-4196",         "kmalloc-8192",         "kmalloc-16384",
>
> "kmalloc-4096"

Good catch!!

>
>> +             "kmalloc-32768",        "kmalloc-65536",
>> +             "kmalloc-131072",       "kmalloc-262144",
>> +             "kmalloc-524288",       "kmalloc-1048576",
>> +             "kmalloc-2097152",      "kmalloc-4194304",
>> +             "kmalloc-8388608",      "kmalloc-16777216",
>> +             "kmalloc-33554432",     "kmalloc-67108864"
>> +     };
>
> On Wed, Apr 22 2015, Andrew Morton <akpm@...ux-foundation.org> wrote:
>
>> You could do something like
>>
>>               kmalloc_caches[i] = create_kmalloc_cache(
>>                                       kmalloc_names[i],
>>                                       kstrtoul(kmalloc_names[i] + 8),
>>                                       flags);
>>
>> here, and remove those weird "96" and "192" cases.
>
> Eww. At least spell 8 as strlen("kmalloc-").
>
>> Or if that's considered too messy, make it
>>
>>       static const struct {
>>               const char *name;
>>               unsigned size;
>>       } kmalloc_cache_info[] = {
>>               { NULL, 0 },
>>               { "kmalloc-96", 96 },
>>               ...
>>       };
>
> I'd vote for this color for the bikeshed :-)
>
> Rasmus

Thanks for the review! I'll come out another version soon.
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