linux-kernel - Re: [PATCH] tracing: add ACCOUNT flag for allocations from marked slab caches

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Date:   Tue, 17 May 2022 06:49:04 +0300
From:   Vasily Averin <vvs@...nvz.org>
To:     Roman Gushchin <roman.gushchin@...ux.dev>,
        Vlastimil Babka <vbabka@...e.cz>
Cc:     Shakeel Butt <shakeelb@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        David Rientjes <rientjes@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Christoph Lameter <cl@...ux.com>, kernel@...nvz.org,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: Re: [PATCH] tracing: add ACCOUNT flag for allocations from marked
 slab caches

On 5/17/22 01:08, Roman Gushchin wrote:
> On Mon, May 16, 2022 at 11:41:27PM +0200, Vlastimil Babka wrote:
>> On 5/16/22 21:10, Shakeel Butt wrote:
>>> On Mon, May 16, 2022 at 11:53 AM Vasily Averin <vvs@...nvz.org> wrote:
>>>>  {
>>>>         void *ret = slab_alloc(cachep, lru, flags, cachep->object_size, _RET_IP_);
>>>>
>>>> +       if (cachep->flags & SLAB_ACCOUNT)
>>>
>>> Should this 'if' be unlikely() or should we trace cachep->flags
>>> explicitly to avoid this branch altogether?
>>
>> Hm I think ideally the tracepoint accepts cachep instead of current
>> cachep->*size parameters and does the necessary extraction and
>> modification in its fast_assign.
> 
> +1 for fast_assign
> 
> Changing flags just for tracing looks a bit excessive.

At the kmem_cache_alloc and kmem_alloc use the same tracing template.
Ok, I'll try to redesign this.