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 BF0A5131740; Thu, 28 Mar 2024 15:59:05 +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=1711641545; cv=none; b=H5mPKrwSdTH6HWTwbVt1DTYvq8dQbJHKgzap88APujKekGVCEvwz0Pm8sm6sIK3g0CheUdOLkZeml0ULM6dBeZ0mvnBpG8ve7B1ikUXolllg0yqKx4Xnm/pS0CCtnzAjwdJ0wuJtZWEuN7m/nDrU+EHv9RXSHrByiXQz96g5Y7Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711641545; c=relaxed/simple; bh=qoqinQw63fGFh+6IC/Y5pgVTD9GppSO7nESSrP07adE=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=fsWGo9rR+5XOCX5Aim42rOLO8ll4CT2hG+ctpve0TvQZimWGtBtjU8IEDauI72eCTqNfDGutXVgwb1IZE4c9SW2pZl44du9FJ8Rx/KRIm4B4R5flC/7vgWLMv1pzdv6C4FqEj44xicl1XmHVbcyDQD5yyqm1VccP3MSIjvtUbDk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZeXxNdYd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZeXxNdYd" Received: by smtp.kernel.org (Postfix) with ESMTPS id 3262FC433B2; Thu, 28 Mar 2024 15:59:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711641545; bh=qoqinQw63fGFh+6IC/Y5pgVTD9GppSO7nESSrP07adE=; h=From:Subject:Date:To:Cc:Reply-To:From; b=ZeXxNdYdDpyc+XN31Wm34tBo8zyeQVjgDnJmmZw7SqlPg/zj94JVdBp6iabFK0Gw2 ITV4o/QB4aAtXsNpLjBnbnj2kuDX6I1b1ezlRqufzDzV165JDLOtFPbnIC11FikLCJ GAqPNRfOsmxNEYDT3tz45gmm0cFTLKOr4n3vjooe/XqU/VyHBpATYmAS+7paJezM2K 9FDJEoWq38AGZ1DKjmwp613+zoL2lGeqIxkb2zRXnwlWVQFL269SZ0hQpir3GsQaC7 Rk1FT4Lf1yvo+YLMWPF194Ct83ik0RLug0gOTvHd5ilV4AMRJk8qEOG7Hqpejk+g3c sE+IDJ1Ruargg== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F760CD1284; Thu, 28 Mar 2024 15:59:05 +0000 (UTC) From: Joel Granados via B4 Relay Subject: [PATCH 0/7] sysctl: Remove sentinel elements from misc directories Date: Thu, 28 Mar 2024 16:57:47 +0100 Message-Id: <20240328-jag-sysctl_remset_misc-v1-0-47c1463b3af2@samsung.com> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAHuTBWYC/x3MSQqAMAxA0atI1hZqncCriEhoo0acaIoo4t0tL t/i/weEPJNAkzzg6WThfYvI0gTshNtIil00GG0KnRutZhyV3GLD0ntahUK/sliFpsqGEmvnCCH Gh6eBr3/cdu/7AeaEmhloAAAA To: Andrew Morton , Muchun Song , Miaohe Lin , Naoya Horiguchi , John Johansen , Paul Moore , James Morris , "Serge E. Hallyn" , David Howells , Jarkko Sakkinen , Kees Cook , Herbert Xu , "David S. Miller" , Jens Axboe , Pavel Begunkov , Atish Patra , Anup Patel , Will Deacon , Mark Rutland , Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: Luis Chamberlain , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org, keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, io-uring@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Joel Granados X-Mailer: b4 0.13-dev-2d940 X-Developer-Signature: v=1; a=openpgp-sha256; l=7724; i=j.granados@samsung.com; h=from:subject:message-id; bh=C5ExU42iQIATTNjm61dOO7nRB4VDW70Mylk1Ch/NE2k=; b=owJ4nAHtARL+kA0DAAoBupfNUreWQU8ByyZiAGYFk8MCISRyCsZWM39FGDZLGap6umXikDNpN y/UcPPR1cdsxokBswQAAQoAHRYhBK5HCVcl5jElzssnkLqXzVK3lkFPBQJmBZPDAAoJELqXzVK3 lkFPlNgL/iKOshbA23YN0uTNsvODr8xCuFjrnb+cdNlPZz3c0ZsZEs5Jf4Nxrtz/mlIPM5CYrgb tLxFHPzllWFljQyXlDt32Y6gBMKvvahcSPUMYzTREmR8avBZLhtO6IfFElpBHSjMWrkXnb0C9Ri PMKWSRBukVgiBwuXHUKP5CqBTyi4HiIRxR7xfZ67tjbUqXdfbYI0+VRHr3eLLxniXJpqrhfzcnE 0V2TanI13+QxTYeLlJPfyaUtoRpA8dD+K0fSpJjqWSSXyMg/iTgIT7LcZA5YHBiD2IkdPBpRoxO SiPAXXa8zmVB3zMHZSQ0Jg5pEtcpkiev1frtqj1lqKsY1UNsRbSIr8hP3CAFbTO8ueuhwNkKo6W E3W+KMVsmBqPCtOPOlDHiYOKMT+7xbeb+UJdmFN9o/cZ3j5KLnp/oEHmEao0VQCY6K4m9vK94UU kMsVPtIH5meae8MuCInGSeeP3ti3V5gT+4o+lm1hKsUJLVQHWrrUSwQjkDWS2DV8z8prsF+g6n5 UE= X-Developer-Key: i=j.granados@samsung.com; a=openpgp; fpr=F1F8E46D30F0F6C4A45FF4465895FAAC338C6E77 X-Endpoint-Received: by B4 Relay for j.granados@samsung.com/default with auth_id=70 X-Original-From: Joel Granados Reply-To: j.granados@samsung.com From: Joel Granados What? These commits remove the sentinel element (last empty element) from the sysctl arrays of all the files under the "mm/", "security/", "ipc/", "init/", "io_uring/", "drivers/perf/" and "crypto/" directories that register a sysctl array. The inclusion of [4] to mainline allows the removal of sentinel elements without behavioral change. This is safe because the sysctl registration code (register_sysctl() and friends) use the array size in addition to checking for a sentinel [1]. Why? By removing the sysctl sentinel elements we avoid kernel bloat as ctl_table arrays get moved out of kernel/sysctl.c into their own respective subsystems. This move was started long ago to avoid merge conflicts; the sentinel removal bit came after Mathew Wilcox suggested it to avoid bloating the kernel by one element as arrays moved out. This patchset will reduce the overall build time size of the kernel and run time memory bloat by about ~64 bytes per declared ctl_table array (more info here [5]). When are we done? There are 4 patchest (25 commits [2]) that are still outstanding to completely remove the sentinels: files under "net/", files under "kernel/" dir, misc dirs (this patchset) and the final set that removes the unneeded check for ->procname == NULL. Testing: * Ran sysctl selftests (./tools/testing/selftests/sysctl/sysctl.sh) * Ran this through 0-day with no errors or warnings Savings in vmlinux: A total of 64 bytes per sentinel is saved after removal; I measured in x86_64 to give an idea of the aggregated savings. The actual savings will depend on individual kernel configuration. * bloat-o-meter - The "yesall" config saves 963 bytes (bloat-o-meter output [6]) - A reduced config [3] saves 452 bytes (bloat-o-meter output [7]) Savings in allocated memory: None in this set but will occur when the superfluous allocations are removed from proc_sysctl.c. I include it here for context. The estimated savings during boot for config [3] are 6272 bytes. See [8] for how to measure it. Comments/feedback greatly appreciated Best Joel [1] https://lore.kernel.org/all/20230809105006.1198165-1-j.granados@samsung.com/ [2] https://git.kernel.org/pub/scm/linux/kernel/git/joel.granados/linux.git/tag/?h=sysctl_remove_empty_elem_v5 [3] https://gist.github.com/Joelgranados/feaca7af5537156ca9b73aeaec093171 [4] https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/ [5] Links Related to the ctl_table sentinel removal: * Good summaries from Luis: https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/ https://lore.kernel.org/all/ZMFizKFkVxUFtSqa@bombadil.infradead.org/ * Patches adjusting sysctl register calls: https://lore.kernel.org/all/20230302204612.782387-1-mcgrof@kernel.org/ https://lore.kernel.org/all/20230302202826.776286-1-mcgrof@kernel.org/ * Discussions about expectations and approach https://lore.kernel.org/all/20230321130908.6972-1-frank.li@vivo.com https://lore.kernel.org/all/20220220060626.15885-1-tangmeng@uniontech.com [6] add/remove: 0/0 grow/shrink: 0/16 up/down: 0/-963 (-963) Function old new delta setup_mq_sysctls 502 499 -3 yama_sysctl_table 128 64 -64 vm_page_writeback_sysctls 512 448 -64 vm_oom_kill_table 256 192 -64 vm_compaction 320 256 -64 page_alloc_sysctl_table 576 512 -64 mq_sysctls 384 320 -64 memory_failure_table 192 128 -64 loadpin_sysctl_table 128 64 -64 key_sysctls 448 384 -64 kernel_io_uring_disabled_table 192 128 -64 kern_do_mounts_initrd_table 128 64 -64 ipc_sysctls 832 768 -64 hugetlb_vmemmap_sysctls 128 64 -64 hugetlb_table 320 256 -64 apparmor_sysctl_table 256 192 -64 Total: Before=440605433, After=440604470, chg -0.00% [7] add/remove: 0/0 grow/shrink: 0/8 up/down: 0/-452 (-452) Function old new delta setup_ipc_sysctls 306 302 -4 vm_page_writeback_sysctls 512 448 -64 vm_oom_kill_table 256 192 -64 page_alloc_sysctl_table 384 320 -64 key_sysctls 384 320 -64 kernel_io_uring_disabled_table 192 128 -64 ipc_sysctls 640 576 -64 hugetlb_table 256 192 -64 Total: Before=8523801, After=8523349, chg -0.01% [8] To measure the in memory savings apply this on top of this patchset. " diff --git i/fs/proc/proc_sysctl.c w/fs/proc/proc_sysctl.c index 37cde0efee57..896c498600e8 100644 --- i/fs/proc/proc_sysctl.c +++ w/fs/proc/proc_sysctl.c @@ -966,6 +966,7 @@ static struct ctl_dir *new_dir(struct ctl_table_set *set, table[0].procname = new_name; table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO; init_header(&new->header, set->dir.header.root, set, node, table, 1); + printk("%ld sysctl saved mem kzalloc\n", sizeof(struct ctl_table)); return new; } @@ -1189,6 +1190,7 @@ static struct ctl_table_header *new_links(struct ctl_dir *dir, s> link_name += len; link++; } + printk("%ld sysctl saved mem kzalloc\n", sizeof(struct ctl_table)); init_header(links, dir->header.root, dir->header.set, node, link_table, head->ctl_table_size); links->nreg = nr_entries; " and then run the following bash script in the kernel: accum=0 for n in $(dmesg | grep kzalloc | awk '{print $3}') ; do accum=$(calc "$accum + $n") done echo $accum Signed-off-by: Joel Granados -- --- Joel Granados (7): memory: Remove the now superfluous sentinel element from ctl_table array security: Remove the now superfluous sentinel element from ctl_table array crypto: Remove the now superfluous sentinel element from ctl_table array initrd: Remove the now superfluous sentinel element from ctl_table array ipc: Remove the now superfluous sentinel element from ctl_table array io_uring: Remove the now superfluous sentinel elements from ctl_table array drivers: perf: Remove the now superfluous sentinel elements from ctl_table array crypto/fips.c | 1 - drivers/perf/riscv_pmu_sbi.c | 1 - init/do_mounts_initrd.c | 1 - io_uring/io_uring.c | 1 - ipc/ipc_sysctl.c | 1 - ipc/mq_sysctl.c | 1 - mm/compaction.c | 1 - mm/hugetlb.c | 1 - mm/hugetlb_vmemmap.c | 1 - mm/memory-failure.c | 1 - mm/oom_kill.c | 1 - mm/page-writeback.c | 1 - mm/page_alloc.c | 1 - security/apparmor/lsm.c | 1 - security/keys/sysctl.c | 1 - security/loadpin/loadpin.c | 1 - security/yama/yama_lsm.c | 1 - 17 files changed, 17 deletions(-) --- base-commit: 4cece764965020c22cff7665b18a012006359095 change-id: 20240320-jag-sysctl_remset_misc-a261f5a7ddea Best regards, -- Joel Granados