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AJvYcCXfx38wrxTRR+JPCBjv4kwjoP+1bzRlQL4bMASUfmz7S9i0qNinFyxlo/zEfOB0zdTF9WDUw9HI+Vgw1Hq1CVfM4X5SxQTdZiFlzbbe X-Gm-Message-State: AOJu0YzaE4iDY7CSXDejW+J3A6mv8pRKv90KLXmoZmBAGP/5Sk8mm1g0 paLbiY6vHt8CPhuN7p72HrvrMmDg74/A4DAanYsADdtjrC1kaKAx X-Google-Smtp-Source: AGHT+IEHNNn4a8XKmxXct+hWuMn/VO2hl+aQXm6B1er+w5jDgCHCa7OkH5FnK4dd5BvS+GN1rLzMNA== X-Received: by 2002:a17:90a:7e0e:b0:2c9:7e9c:9637 with SMTP id 98e67ed59e1d1-2ca35c2a6dcmr6426513a91.13.1720698697629; Thu, 11 Jul 2024 04:51:37 -0700 (PDT) Received: from [192.168.255.10] ([43.132.141.20]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2ca34e854ddsm5505815a91.25.2024.07.11.04.51.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Jul 2024 04:51:37 -0700 (PDT) Message-ID: Date: Thu, 11 Jul 2024 19:51:33 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/2] mm/memcg: alignment memcg_data define condition To: Vlastimil Babka , alexs@kernel.org, Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Randy Dunlap , Yoann Congal , Masahiro Yamada , Petr Mladek , Suren Baghdasaryan References: <20240710054336.190410-1-alexs@kernel.org> <42afbce8-7746-438f-ba3a-c997a2c702e5@suse.cz> Content-Language: en-US From: Alex Shi In-Reply-To: <42afbce8-7746-438f-ba3a-c997a2c702e5@suse.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/11/24 4:13 PM, Vlastimil Babka wrote: > On 7/10/24 7:43 AM, alexs@kernel.org wrote: >> From: "Alex Shi (Tencent)" >> >> commit 21c690a349ba ("mm: introduce slabobj_ext to support slab object >> extensions") changed the folio/page->memcg_data define condition from >> MEMCG to SLAB_OBJ_EXT. And selected SLAB_OBJ_EXT for MEMCG, just for >> SLAB_MATCH(memcg_data, obj_exts), even no other relationship between them. >> >> Above action make memcg_data exposed and include SLAB_OBJ_EXT for >> !MEMCG. That's incorrect in logcial and pay on code size. >> >> As Vlastimil Babka suggested, let's add _unused_slab_obj_ext for >> SLAB_MATCH for slab.obj_exts while !MEMCG. That could resolve the match >> issue, clean up the feature logical. And decouple the SLAB_OBJ_EXT from >> MEMCG in next patch. >> >> Signed-off-by: Alex Shi (Tencent) >> Cc: Randy Dunlap >> Cc: Yoann Congal >> Cc: Masahiro Yamada >> Cc: Petr Mladek >> Cc: Suren Baghdasaryan >> Cc: Vlastimil Babka >> --- >> v1->v3: take Vlastimil's suggestion and move SLAB_OBJ_EXT/MEMCG decouple >> to 2nd patch. >> --- >> include/linux/mm_types.h | 8 ++++++-- >> mm/slab.h | 4 ++++ >> 2 files changed, 10 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h >> index ef09c4eef6d3..4ac3abc673d3 100644 >> --- a/include/linux/mm_types.h >> +++ b/include/linux/mm_types.h >> @@ -180,8 +180,10 @@ struct page { >> /* Usage count. *DO NOT USE DIRECTLY*. See page_ref.h */ >> atomic_t _refcount; >> >> -#ifdef CONFIG_SLAB_OBJ_EXT >> +#ifdef CONFIG_MEMCG >> unsigned long memcg_data; >> +#elif defined(CONFIG_SLAB_OBJ_EXT) >> + unsigned long _unused_slab_obj_ext; >> #endif >> >> /* >> @@ -343,8 +345,10 @@ struct folio { >> }; >> atomic_t _mapcount; >> atomic_t _refcount; >> -#ifdef CONFIG_SLAB_OBJ_EXT >> +#ifdef CONFIG_MEMCG >> unsigned long memcg_data; >> +#elif defined(CONFIG_SLAB_OBJ_EXT) >> + unsigned long _unused_slab_obj_ext; >> #endif >> #if defined(WANT_PAGE_VIRTUAL) >> void *virtual; >> diff --git a/mm/slab.h b/mm/slab.h >> index 3586e6183224..8ffdd4f315f8 100644 >> --- a/mm/slab.h >> +++ b/mm/slab.h >> @@ -98,7 +98,11 @@ SLAB_MATCH(flags, __page_flags); >> SLAB_MATCH(compound_head, slab_cache); /* Ensure bit 0 is clear */ >> SLAB_MATCH(_refcount, __page_refcount); >> #ifdef CONFIG_SLAB_OBJ_EXT >> +#ifdef CONFIG_MEMCG >> SLAB_MATCH(memcg_data, obj_exts); >> +#else >> +SLAB_MATCH(_unused_slab_obj_ext, obj_exts); >> +#endif >> #endif > > Why not also #ifdef / #elif like above, instead of this nesting? Uh, it works too if MEMCG/SLAB_OBJ_EXT decoupled. but right, it could be written with #ifdef/#elif. Thanks Alex > >> #undef SLAB_MATCH >> static_assert(sizeof(struct slab) <= sizeof(struct page)); >