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b=o3qex/OpMM8/2lZGb3DNxYt2UeWKGoolYnOmw3tnZp1VaRLMON3v9nZusDk1IO1Cl 79sp7ZYixCuEMwQ154T9Z+DDLUH+ApRnc/HyOgpySTOy0xTOtetN0DYx6NHwDfKKyw bwFh2sslOwUNVzmOGtSmmKozYC6N5q6nGCxi48yXEzLTO0fxYza2oSpEW43Nk1KOOs CaoMfA4O/ElaZP9OVJMi1CTJcMhrQoxTdeuZOe97vQ3Oi9/OkQOhh1uA2yZfHX3bXM JYzuNJNw3uzMn/nD1sAG+HLMCx3eJZfngyMlvxDZ7noiuYfTOVKsWbUxuQce4u6xEY VQFN3QiVgX3hg== Message-ID: <076dc6ce-4895-41d7-b9c1-9ec872e7c8b8@kernel.org> Date: Thu, 16 Jul 2026 16:47:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 09/12] mm/slab: introduce slab_obj_ext_has_codetag() Content-Language: en-US To: Suren Baghdasaryan Cc: Harry Yoo , Hao Li , Shakeel Butt , Alexander Potapenko , Marco Elver , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org References: <20260715-b4-objext_split-v1-0-9a49c4ccf4c3@kernel.org> <20260715-b4-objext_split-v1-9-9a49c4ccf4c3@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: 771qo867uztw84j9hxadnufhkijbdsxo X-Rspamd-Queue-Id: B1A7840007 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1784213279-37316 X-HE-Meta: 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 CT0VSWKx PjDd43a8Pekoj90ubE+laCYT+3Yrzf601fGRpd1EnEKMSgQCcRibNVVzgx77kVfc28ne5dsQ7OgHKC/6piek4kXDBJdubG7zpfjqYQ8ZcdcW6Vy6DUgVIf4uY2sL/Fl3fsEZDGoUbMnRZ/9C7Gg5dkM2heK5s16qBTmFygjJvTdSihdoxenZFg+Z54RS1ImFKYYNfgLSa8RZ4rkeRaPB97+XF3SEQ9FZQZ63rjxYltPraUMiytBrj4bu3c8uUtefveoo55u9OQiN3lOQkgo2Y61wKTOFwtxkaV4mfEU2i7tww3LAq2PBfU04VawGLQh19YhoHxvtkJkA1ml8EAKqoIO5fIUg+QzRujKc+cvG5HAGrGmEOfeerXUhxBhkWuahNNIw7 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/16/26 06:25, Suren Baghdasaryan wrote: > On Wed, Jul 15, 2026 at 3:11 AM Vlastimil Babka (SUSE) > wrote: >> >> mem_alloc_profiling_enabled() allows evaluating (with a static key) if >> memory profiling is currently enabled. mem_profiling_support is a >> variable where false means it's not possible to enable it anymore, >> because the system was booted with "never" or it was later shut down. >> This is possible to query by mem_alloc_profiling_permanently_disabled(). >> >> To make slabobj_ext array size handling dynamic, we need a snapshot of >> mem_alloc_profiling_permanently_disabled() early in boot, so that's not >> affected by a later shutdown. We also need it to be static key based for >> performance. Neither mem_alloc_profiling_enabled() nor >> mem_alloc_profiling_permanently_disabled() satisfy this. >> >> Therefore introduce slab_obj_ext_has_codetag() with an underlying static >> key for that use case. Its state is made to reflect the result of >> mem_alloc_profiling_permanently_disabled() during kmem_cache_init(), >> which does happen after setup_early_mem_profiling(). >> >> Signed-off-by: Vlastimil Babka (SUSE) > > Reviewed-by: Suren Baghdasaryan Thanks! >> +/* >> + * Make sure the static key used by slab_obj_ext_has_codetag() reflects the >> + * value of !mem_alloc_profiling_permanently_disabled() >> + * >> + * Any later mem alloc profiling shutdown won't be reflected in the static key >> + * because obj_exts with codetags might already exist. >> + */ >> +static void __init slab_obj_ext_has_codetag_init(void) >> +{ >> + bool key_enabled = IS_ENABLED(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT); > > nit: This seems a bit indirect. Reader needs to remember that > slab_obj_ext_has_codetag_key is initialized based on > CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT. Wouldn't below code be > simpler?: > > bool need_codetag = !mem_alloc_profiling_permanently_disabled(); > if (need_codetag != static_key_enabled(&slab_obj_ext_has_codetag_key)) { > if (need_codetag) > static_branch_enable(&slab_obj_ext_has_codetag_key); > else > static_branch_disable(&slab_obj_ext_has_codetag_key); > } > > It might be less performant but who cares, it's __init function used > only one time. Good idea, will do!