From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B3E54226CFE for ; Fri, 6 Mar 2026 01:47:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772761660; cv=none; b=DoOKR2S6R+P5FG+bLhmMvjuw0zZPBsbxgPh22jZusasGXxDQlTwOnnA02WVibnXdv9lG0Y5Jw/6SRGcLr/OnMZhlh5fSS/HC9cCcMOEakaRMVLE7d3H6hbTBKch3mNnXQVboi5qk6bqRsDSjgO8EGSE1fHeKMBKkTJoQrDVXA78= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772761660; c=relaxed/simple; bh=oe2URUUYqAJI1ok/3Q+sbD2WqAZjyNGgxlj1VYgq9Nk=; h=Date:To:From:Subject:Message-Id; b=uakQV5DHrBDi069m8qJ/rzxWAYxZFiK+7vsVJulWPeea0s50cIV6yPyBBSKRSn43/9FtoRHO6DeJKMr4d7bUWHpv+HTjzue38Iro65RsRdvzxV88CdNVKnc8ipednVLjZmvBMQhKnQyPlqczoN5AoIE99T4G1Kw+tTqWgthwb84= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=mBUiHGPf; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="mBUiHGPf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3D1EC2BC87; Fri, 6 Mar 2026 01:47:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1772761660; bh=oe2URUUYqAJI1ok/3Q+sbD2WqAZjyNGgxlj1VYgq9Nk=; h=Date:To:From:Subject:From; b=mBUiHGPfWL970H1SW6/asj4xl3Imd2dcyyKvT/MeQNhMupNiAz0YDBqHVmKmWeR3/ qjkMyVFohvmaHzs5DZSGiqhfmNUF/FsgJjGAaR0o/Zlx1O8lVN/uPuF+nacmM4uyQI 25AeZK23n7ryGa8h2gQhZahjHUpxf1dbOy4N0mRs= Date: Thu, 05 Mar 2026 17:47:39 -0800 To: mm-commits@vger.kernel.org,tj@kernel.org,dennis@kernel.org,cl@gentwo.org,zenghongling@kylinos.cn,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-percpu-internalh-optimise-pcpu_chunk_struct-to-save-memory.patch added to mm-new branch Message-Id: <20260306014739.F3D1EC2BC87@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/percpu-internal.h: optimise pcpu_chunk_struct to save memory has been added to the -mm mm-new branch. Its filename is mm-percpu-internalh-optimise-pcpu_chunk_struct-to-save-memory.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-percpu-internalh-optimise-pcpu_chunk_struct-to-save-memory.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: zenghongling Subject: mm/percpu-internal.h: optimise pcpu_chunk_struct to save memory Date: Thu, 5 Mar 2026 15:30:43 +0800 The pcpu_chunk_struct has a hole of 4 bytes and pushes the struct to three cachelines. Relocating the three booleans upwards allows for the struct to only use two cachelines. Before: struct pcpu_chunk { struct list_head list; /* 0 16 */ int free_bytes; /* 16 4 */ struct pcpu_block_md chunk_md; /* 20 32 */ /* XXX 4 bytes hole, try to pack */ long unsigned int * bound_map; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */ void * base_addr __attribute__((__aligned__(64))); /* 64 8 */ long unsigned int * alloc_map; /* 72 8 */ struct pcpu_block_md * md_blocks; /* 80 8 */ void * data; /* 88 8 */ bool immutable; /* 96 1 */ bool isolated; /* 97 1 */ /* XXX 2 bytes hole, try to pack */ int start_offset; /* 100 4 */ int end_offset; /* 104 4 */ /* XXX 4 bytes hole, try to pack */ struct obj_cgroup * * obj_cgroups; /* 112 8 */ int nr_pages; /* 120 4 */ int nr_populated; /* 124 4 */ /* --- cacheline 2 boundary (128 bytes) --- */ int nr_empty_pop_pages; /* 128 4 */ /* XXX 4 bytes hole, try to pack */ long unsigned int populated[]; /* 136 0 */ /* size: 192, cachelines: 3, members: 17 */ /* sum members: 122, holes: 4, sum holes: 14 */ /* padding: 56 */ /* forced alignments: 1 */ } __attribute__((__aligned__(64))); After: struct pcpu_chunk { struct list_head list; /* 0 16 */ int free_bytes; /* 16 4 */ struct pcpu_block_md chunk_md; /* 20 32 */ /* XXX 4 bytes hole, try to pack */ long unsigned int * bound_map; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */ void * base_addr __attribute__((__aligned__(64))); /* 64 8 */ long unsigned int * alloc_map; /* 72 8 */ struct pcpu_block_md * md_blocks; /* 80 8 */ void * data; /* 88 8 */ bool immutable; /* 96 1 */ bool isolated; /* 97 1 */ /* XXX 2 bytes hole, try to pack */ int start_offset; /* 100 4 */ int end_offset; /* 104 4 */ int nr_empty_pop_pages; /* 108 4 */ struct obj_cgroup * * obj_cgroups; /* 112 8 */ int nr_pages; /* 120 4 */ int nr_populated; /* 124 4 */ /* --- cacheline 2 boundary (128 bytes) --- */ long unsigned int populated[]; /* 128 0 */ /* size: 128, cachelines: 2, members: 17 */ /* sum members: 122, holes: 2, sum holes: 6 */ /* forced alignments: 1 */ } __attribute__((__aligned__(64))); Link: https://lkml.kernel.org/r/20260305073043.571691-1-zenghongling@kylinos.cn Signed-off-by: zenghongling Cc: Christoph Lameter Cc: Dennis Zhou Cc: Hongling Zeng Cc: Tejun Heo Signed-off-by: Andrew Morton --- mm/percpu-internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/percpu-internal.h~mm-percpu-internalh-optimise-pcpu_chunk_struct-to-save-memory +++ a/mm/percpu-internal.h @@ -77,13 +77,13 @@ struct pcpu_chunk { int end_offset; /* additional area required to have the region end page aligned */ + int nr_empty_pop_pages; /* # of empty populated pages */ #ifdef NEED_PCPUOBJ_EXT struct pcpuobj_ext *obj_exts; /* vector of object cgroups */ #endif int nr_pages; /* # of pages served by this chunk */ int nr_populated; /* # of populated pages */ - int nr_empty_pop_pages; /* # of empty populated pages */ unsigned long populated[]; /* populated bitmap */ }; _ Patches currently in -mm which might be from zenghongling@kylinos.cn are mm-percpu-internalh-optimise-pcpu_chunk_struct-to-save-memory.patch