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 9CDE642A83 for ; Wed, 27 Mar 2024 19:40:34 +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=1711568434; cv=none; b=jj1+Y8naheDZ1TEP2ovji//yDK2T6JN53nJjdNC7mc4dNOyqXohKDekNCmBrmi6ZT2Ysx3OnqrPWy/ya0YrrfaCTyWqGwOIuXGNawRF/8OFc7wrqX/jKxNkjip2xgzpqGVcG+g5yOEt40FpSss+hNW3YdaOMwU+I4rABQ+AVlfc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711568434; c=relaxed/simple; bh=TJ9rNXrcISSuzq7/HXv/Ean2Ees70jRvsNU2wZhnpo4=; h=Date:To:From:Subject:Message-Id; b=HnrDnUV6VqJuIHukNyKUH1rv0zI7HBlja77LdKpzhFwwqV5anhP8Ih6EoqoNOV6ku+35ImIi0YXD43LwS4Uts9U+3UEhYAGFFyNlvYv7PHBMQPG2fHJIFv1wX9yf3GsNcfSOzkkvCSa9k9D8MJz9VHvElLmsqvTMY/PslttdmCE= 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=zig+U0KN; 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="zig+U0KN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09685C433C7; Wed, 27 Mar 2024 19:40:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1711568434; bh=TJ9rNXrcISSuzq7/HXv/Ean2Ees70jRvsNU2wZhnpo4=; h=Date:To:From:Subject:From; b=zig+U0KNAjivsesWPkr0HtMu4Rp16exnaNMbM+cK3nWuXfMem0MRCCrF8swJKeKjG PI6NNDmbLU0+PGKK4QXsCwaw4/2sBae0h/FR700raousj/JXNdDapDhxYJnTbRCaWQ EgKxkviXWNHd+HoTHAjdl7lfRx9MhwrseQShCqZY= Date: Wed, 27 Mar 2024 12:40:33 -0700 To: mm-commits@vger.kernel.org,wangkefeng.wang@huawei.com,surenb@google.com,sunnanyong@huawei.com,peterx@redhat.com,lokeshgidra@google.com,Liam.Howlett@oracle.com,david@redhat.com,axelrasmussen@google.com,zhangpeng362@huawei.com,akpm@linux-foundation.org From: Andrew Morton Subject: + userfaultfd-early-return-in-dup_userfaultfd.patch added to mm-unstable branch Message-Id: <20240327194034.09685C433C7@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: userfaultfd: early return in dup_userfaultfd() has been added to the -mm mm-unstable branch. Its filename is userfaultfd-early-return-in-dup_userfaultfd.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/userfaultfd-early-return-in-dup_userfaultfd.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: ZhangPeng Subject: userfaultfd: early return in dup_userfaultfd() Date: Wed, 27 Mar 2024 17:08:35 +0800 When vma->vm_userfaultfd_ctx.ctx is NULL, vma->vm_flags should have cleared __VM_UFFD_FLAGS. Therefore, there is no need to down_write or clear the flag, which will affect fork performance. Fix this by returning early if octx is NULL in dup_userfaultfd(). By applying this patch we can get a 1.3% performance improvement for lmbench fork_prot. Results are as follows: base early return Process fork+exit: 419.1106 413.4804 Link: https://lkml.kernel.org/r/20240327090835.3232629-1-zhangpeng362@huawei.com Signed-off-by: ZhangPeng Reviewed-by: Peter Xu Cc: Axel Rasmussen Cc: David Hildenbrand Cc: Kefeng Wang Cc: Liam R. Howlett Cc: Lokesh Gidra Cc: Nanyong Sun Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton --- fs/userfaultfd.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/fs/userfaultfd.c~userfaultfd-early-return-in-dup_userfaultfd +++ a/fs/userfaultfd.c @@ -657,7 +657,10 @@ int dup_userfaultfd(struct vm_area_struc struct userfaultfd_fork_ctx *fctx; octx = vma->vm_userfaultfd_ctx.ctx; - if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { + if (!octx) + return 0; + + if (!(octx->features & UFFD_FEATURE_EVENT_FORK)) { vma_start_write(vma); vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; userfaultfd_set_vm_flags(vma, vma->vm_flags & ~__VM_UFFD_FLAGS); _ Patches currently in -mm which might be from zhangpeng362@huawei.com are userfaultfd-early-return-in-dup_userfaultfd.patch filemap-replace-pte_offset_map-with-pte_offset_map_nolock.patch