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 2728AC77B6C for ; Tue, 28 Mar 2023 23:21:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229727AbjC1XVL (ORCPT ); Tue, 28 Mar 2023 19:21:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35214 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229622AbjC1XVJ (ORCPT ); Tue, 28 Mar 2023 19:21:09 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 66EFB2698 for ; Tue, 28 Mar 2023 16:21:06 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id F01FF618FE for ; Tue, 28 Mar 2023 23:21:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52C77C4339C; Tue, 28 Mar 2023 23:21:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1680045665; bh=oSO/tE/3IGlhzEoZELd5KngXJFHI/UhAUmS8Vn6sO+Q=; h=Date:To:From:Subject:From; b=0gIWEs0alLpZdM9YEwTvzQLFqhFVkWRyx8HUw2hFE/zOdOLu/exmSKZ937C5TuHSB jhvR1ElmfKz52E9+hwTvGQj0Ox0xbq5xqTSw5LvGDYjCFSW+hl/71OCP0FJT85vdID T+iSNyKp+Hkj9m0o6k6TnFRJQMXfTkNbij2dNc5s= Date: Tue, 28 Mar 2023 16:21:04 -0700 To: mm-commits@vger.kernel.org, will@kernel.org, torvalds@linux-foundation.org, riel@redhat.com, peterz@infradead.org, nadav.amit@gmail.com, mpe@ellerman.id.au, luto@kernel.org, dave.hansen@linux.intel.com, christophe.leroy@csgroup.eu, catalin.marinas@arm.com, npiggin@gmail.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] kthread-simplify-kthread_use_mm-refcounting.patch removed from -mm tree Message-Id: <20230328232105.52C77C4339C@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The quilt patch titled Subject: kthread: simplify kthread_use_mm refcounting has been removed from the -mm tree. Its filename was kthread-simplify-kthread_use_mm-refcounting.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Nicholas Piggin Subject: kthread: simplify kthread_use_mm refcounting Date: Fri, 3 Feb 2023 17:18:33 +1000 Patch series "shoot lazy tlbs (lazy tlb refcount scalability improvement)", v7. This series improves scalability of context switching between user and kernel threads on large systems with a threaded process spread across a lot of CPUs. Discussion of v6 here: https://lore.kernel.org/linux-mm/20230118080011.2258375-1-npiggin@gmail.com/ This patch (of 5): Remove the special case avoiding refcounting when the mm to be used is the same as the kernel thread's active (lazy tlb) mm. kthread_use_mm() should not be such a performance critical path that this matters much. This simplifies a later change to lazy tlb mm refcounting. Link: https://lkml.kernel.org/r/20230203071837.1136453-1-npiggin@gmail.com Link: https://lkml.kernel.org/r/20230203071837.1136453-2-npiggin@gmail.com Signed-off-by: Nicholas Piggin Acked-by: Linus Torvalds Cc: Andy Lutomirski Cc: Catalin Marinas Cc: Dave Hansen Cc: Linus Torvalds Cc: Nadav Amit Cc: Peter Zijlstra Cc: Rik van Riel Cc: Will Deacon Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Christophe Leroy Signed-off-by: Andrew Morton --- kernel/kthread.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) --- a/kernel/kthread.c~kthread-simplify-kthread_use_mm-refcounting +++ a/kernel/kthread.c @@ -1415,14 +1415,13 @@ void kthread_use_mm(struct mm_struct *mm WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); WARN_ON_ONCE(tsk->mm); + mmgrab(mm); + task_lock(tsk); /* Hold off tlb flush IPIs while switching mm's */ local_irq_disable(); active_mm = tsk->active_mm; - if (active_mm != mm) { - mmgrab(mm); - tsk->active_mm = mm; - } + tsk->active_mm = mm; tsk->mm = mm; membarrier_update_current_mm(mm); switch_mm_irqs_off(active_mm, mm, tsk); @@ -1439,12 +1438,9 @@ void kthread_use_mm(struct mm_struct *mm * memory barrier after storing to tsk->mm, before accessing * user-space memory. A full memory barrier for membarrier * {PRIVATE,GLOBAL}_EXPEDITED is implicitly provided by - * mmdrop(), or explicitly with smp_mb(). + * mmdrop(). */ - if (active_mm != mm) - mmdrop(active_mm); - else - smp_mb(); + mmdrop(active_mm); } EXPORT_SYMBOL_GPL(kthread_use_mm); _ Patches currently in -mm which might be from npiggin@gmail.com are