From: Jens Axboe <axboe@kernel.dk>
To: Vlastimil Babka <vbabka@suse.cz>,
LKML <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Jesper Dangaard Brouer <hawk@kernel.org>,
Christoph Lameter <cl@linux.com>,
David Rientjes <rientjes@google.com>,
Pekka Enberg <penberg@kernel.org>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Howard McLauchlan <hmclauchlan@fb.com>
Cc: bpf@vger.kernel.org
Subject: Re: [PATCH] mm: don't call should_failslab() for !CONFIG_FAILSLAB
Date: Thu, 7 Oct 2021 09:50:11 -0600 [thread overview]
Message-ID: <082f30c7-9a7c-b2de-6d30-99fa38150d48@kernel.dk> (raw)
In-Reply-To: <2dfc6273-6cdd-f4f5-bed9-400873ac9152@suse.cz>
On 10/7/21 9:32 AM, Vlastimil Babka wrote:
> On 10/5/21 17:31, Jens Axboe wrote:
>> Allocations can be a very hot path, and this out-of-line function
>> call is noticeable.
>>
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>
> It used to be inline b4 (hi, Konstantin!) and then was converted to be like
> this intentionally :/
>
> See 4f6923fbb352 ("mm: make should_failslab always available for fault
> injection")
>
> And now also kernel/bpf/verifier.c contains:
> BTF_ID(func, should_failslab)
>
> I think either your or Andrew's version will break this BTF_ID thing, at the
> very least.
>
> But I do strongly agree that putting unconditionally a non-inline call into
> slab allocator fastpath sucks. Can we make it so that bpf can only do these
> overrides when CONFIG_FAILSLAB is enabled?
> I don't know, perhaps putting this BTF_ID() in #ifdef as well, or providing
> a dummy that is always available (so that nothing breaks), but doesn't
> actually affect slab_pre_alloc_hook() unless CONFIG_FAILSLAB has been enabled?
That seems to be the right approach, limiting it on it actually being enabled
and a function call.
--
Jens Axboe
next prev parent reply other threads:[~2021-10-07 15:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-05 15:31 [PATCH] mm: don't call should_failslab() for !CONFIG_FAILSLAB Jens Axboe
2021-10-05 21:18 ` Andrew Morton
2021-10-05 21:20 ` Jens Axboe
2021-10-07 15:32 ` Vlastimil Babka
2021-10-07 15:50 ` Jens Axboe [this message]
2021-10-07 16:36 ` Konstantin Ryabitsev
2024-05-27 9:34 ` Mateusz Guzik
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