From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1105BEE020A for ; Wed, 13 Sep 2023 19:28:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232399AbjIMT2d (ORCPT ); Wed, 13 Sep 2023 15:28:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41416 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232400AbjIMT2d (ORCPT ); Wed, 13 Sep 2023 15:28:33 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20E101999 for ; Wed, 13 Sep 2023 12:28:29 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9666C433C8; Wed, 13 Sep 2023 19:28:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1694633308; bh=ZAIB92OgE2GTXY38NWRvFiSK1hfVtIvBfiYs8mX6BKU=; h=Date:To:From:Subject:From; b=zG8svbZBTJlAeEEofSeFlA04pGyw2kg+6FvVyH7JFalr7rccGyhkewTVngFGtPrWP hwFShtx1LkKYmIGUq6XN16Hcy0OnY2knne5pPRgSsEzNahKrjhogo3jKEyvo1N4FNP 89swwUZyn0/JWPfW2ULsSvLkfn2yKl69sCMMjFBM= Date: Wed, 13 Sep 2023 12:28:28 -0700 To: mm-commits@vger.kernel.org, vbabka@suse.cz, osalvador@suse.de, glider@google.com, eugenis@google.com, elver@google.com, dvyukov@google.com, andreyknvl@gmail.com, andreyknvl@google.com, akpm@linux-foundation.org From: Andrew Morton Subject: + lib-stackdepot-check-disabled-flag-when-fetching.patch added to mm-unstable branch Message-Id: <20230913192828.A9666C433C8@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: lib/stackdepot: check disabled flag when fetching has been added to the -mm mm-unstable branch. Its filename is lib-stackdepot-check-disabled-flag-when-fetching.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-stackdepot-check-disabled-flag-when-fetching.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm 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 the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Andrey Konovalov Subject: lib/stackdepot: check disabled flag when fetching Date: Wed, 13 Sep 2023 19:14:26 +0200 Patch series "stackdepot: allow evicting stack traces", v2. Currently, the stack depot grows indefinitely until it reaches its capacity. Once that happens, the stack depot stops saving new stack traces. This creates a problem for using the stack depot for in-field testing and in production. For such uses, an ideal stack trace storage should: 1. Allow saving fresh stack traces on systems with a large uptime while limiting the amount of memory used to store the traces; 2. Have a low performance impact. Implementing #1 in the stack depot is impossible with the current keep-forever approach. This series targets to address that. Issue #2 is left to be addressed in a future series. This series changes the stack depot implementation to allow evicting unneeded stack traces from the stack depot. The users of the stack depot can do that via new stack_depot_save_flags(STACK_DEPOT_FLAG_GET) and stack_depot_put APIs. Internal changes to the stack depot code include: 1. Storing stack traces in fixed-frame-sized slots; the slot size is controlled via CONFIG_STACKDEPOT_MAX_FRAMES (vs precisely-sized slots in the current implementation); 2. Keeping available slots in a freelist (vs keeping an offset to the next free slot); 3. Using a read/write lock for synchronization (vs a lock-free approach combined with a spinlock). This series also integrates the eviction functionality in the tag-based KASAN modes. Despite wasting some space on rounding up the size of each stack record, with CONFIG_STACKDEPOT_MAX_FRAMES=32, the tag-based KASAN modes end up consuming ~5% less memory in stack depot during boot (with the default stack ring size of 32k entries). The reason for this is the eviction of irrelevant stack traces from the stack depot, which frees up space for other stack traces. For other tools that heavily rely on the stack depot, like Generic KASAN and KMSAN, this change leads to the stack depot capacity being reached sooner than before. However, as these tools are mainly used in fuzzing scenarios where the kernel is frequently rebooted, this outcome should be acceptable. There is no measurable boot time performance impact of these changes for KASAN on x86-64. I haven't done any tests for arm64 modes (the stack depot without performance optimizations is not suitable for intended use of those anyway), but I expect a similar result. Obtaining and copying stack trace frames when saving them into stack depot is what takes the most time. This series does not yet provide a way to configure the maximum size of the stack depot externally (e.g. via a command-line parameter). This will be added in a separate series, possibly together with the performance improvement changes. This patch (of 19): Do not try fetching a stack trace from the stack depot if the stack_depot_disabled flag is enabled. Link: https://lkml.kernel.org/r/cover.1694625260.git.andreyknvl@google.com Link: https://lkml.kernel.org/r/66bf1f0ad22d2c49ef500893340c71355b71d092.1694625260.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Alexander Potapenko Cc: Andrey Konovalov Cc: Andrey Konovalov Cc: Dmitry Vyukov Cc: Evgenii Stepanov Cc: Marco Elver Cc: Oscar Salvador Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- lib/stackdepot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/lib/stackdepot.c~lib-stackdepot-check-disabled-flag-when-fetching +++ a/lib/stackdepot.c @@ -477,7 +477,7 @@ unsigned int stack_depot_fetch(depot_sta */ kmsan_unpoison_memory(entries, sizeof(*entries)); - if (!handle) + if (!handle || stack_depot_disabled) return 0; if (parts.pool_index > pool_index_cached) { _ Patches currently in -mm which might be from andreyknvl@google.com are lib-stackdepot-check-disabled-flag-when-fetching.patch lib-stackdepot-simplify-__stack_depot_save.patch lib-stackdepot-drop-valid-bit-from-handles.patch lib-stackdepot-add-depot_fetch_stack-helper.patch lib-stackdepot-use-fixed-sized-slots-for-stack-records.patch lib-stackdepot-fix-and-clean-up-atomic-annotations.patch lib-stackdepot-rework-helpers-for-depot_alloc_stack.patch lib-stackdepot-rename-next_pool_required-to-new_pool_required.patch lib-stackdepot-store-next-pool-pointer-in-new_pool.patch lib-stackdepot-store-free-stack-records-in-a-freelist.patch lib-stackdepot-use-read-write-lock.patch lib-stackdepot-use-list_head-for-stack-record-links.patch kmsan-use-stack_depot_save-instead-of-__stack_depot_save.patch lib-stackdepot-kasan-add-flags-to-__stack_depot_save-and-rename.patch lib-stackdepot-add-refcount-for-records.patch lib-stackdepot-allow-users-to-evict-stack-traces.patch kasan-remove-atomic-accesses-to-stack-ring-entries.patch kasan-check-object_size-in-kasan_complete_mode_report_info.patch kasan-use-stack_depot_put-for-tag-based-modes.patch