From: David Hildenbrand <david@redhat.com>
To: Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Alexander Potapenko <glider@google.com>,
Kees Cook <keescook@chromium.org>,
Michal Hocko <mhocko@kernel.org>,
Mateusz Nosek <mateusznosek0@gmail.com>
Subject: Re: [PATCH 3/3] mm, page_alloc: reduce static keys in prep_new_page()
Date: Tue, 27 Oct 2020 10:10:40 +0100 [thread overview]
Message-ID: <93ab79df-cf8c-294b-3ed1-8a563e4a452b@redhat.com> (raw)
In-Reply-To: <20201026173358.14704-4-vbabka@suse.cz>
On 26.10.20 18:33, Vlastimil Babka wrote:
> prep_new_page() will always zero a new page (regardless of __GFP_ZERO) when
> init_on_alloc is enabled, but will also always skip zeroing if the page was
> already zeroed on free by init_on_free or page poisoning.
>
> The latter check implemented by free_pages_prezeroed() can involve two
> different static keys. As prep_new_page() is really a hot path, let's introduce
> a single static key free_pages_not_prezeroed for this purpose and initialize it
> in init_mem_debugging().
Is this actually observable in practice? This smells like
micro-optimization to me.
Also, I thought the whole reason for static keys is to have basically no
overhead at runtime, so I wonder if replacing two static key checks by a
single one actually makes *some* difference.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-10-27 9:10 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-26 17:33 [PATCH 0/3] optimize handling of memory debugging parameters Vlastimil Babka
2020-10-26 17:33 ` [PATCH 1/3] mm, page_alloc: do not rely on the order of page_poison and init_on_alloc/free parameters Vlastimil Babka
2020-10-27 9:03 ` David Hildenbrand
2020-10-27 9:58 ` Vlastimil Babka
2020-10-27 9:58 ` David Hildenbrand
2020-10-28 8:31 ` Mike Rapoport
2020-10-26 17:33 ` [PATCH 2/3] mm, page_poison: use static key more efficiently Vlastimil Babka
2020-10-27 9:07 ` David Hildenbrand
2020-10-30 16:27 ` Luis Chamberlain
2020-10-30 22:56 ` Vlastimil Babka
2020-11-11 13:29 ` Luis Chamberlain
2020-10-26 17:33 ` [PATCH 3/3] mm, page_alloc: reduce static keys in prep_new_page() Vlastimil Babka
2020-10-27 9:10 ` David Hildenbrand [this message]
2020-10-27 11:05 ` Vlastimil Babka
2020-10-27 13:32 ` Vlastimil Babka
2020-10-27 17:41 ` Vlastimil Babka
2020-10-28 8:38 ` David Hildenbrand
2020-10-29 17:37 ` Alexander Potapenko
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