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 EC34E8BEB for ; Tue, 13 Feb 2024 00:33:23 +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=1707784404; cv=none; b=VQDLXJZJURL8u0IWOpQFkpuy4RR50eZoGdaMBRlafchYuyA5xn8ZLVSy4DzsgrN8AwZ4t1oeoAYOKuqWsjjRqTuTAa/5erYdOjVLCznmZwqwD7UXfdV9x0CEfPyc5kGTVVvLamK7ukqBtmwvUdg3BGV1izCXPEfaF2PtHQ0ih/Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707784404; c=relaxed/simple; bh=DkOde1QJidgjsDBFQD7FQBrzBrAKS/CBW9qiJ5g15ZM=; h=Date:To:From:Subject:Message-Id; b=ACwJ5m5kyJjsGafdx/0/Kg11OSy08kpSD0q/GXeN7LbDk7RWl+ufDVmUwmhzL00BXWq08Do3o1Wx6VX9wwjcCif+8ITINo4w29+QIgmWARJlmfLmX/6YI6KoRCsWdoCoj0lfBGWtLONjaFQRhh5t1rwczZzw3hXrOYZRyBCMsoo= 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=OpJvSFPG; 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="OpJvSFPG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 508EBC433C7; Tue, 13 Feb 2024 00:33:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1707784403; bh=DkOde1QJidgjsDBFQD7FQBrzBrAKS/CBW9qiJ5g15ZM=; h=Date:To:From:Subject:From; b=OpJvSFPGGcAP0EFZY2wXn6XFE3DiTFS0IbmPFleWeK2Gs0l4oKdFWrbFDwMgdIYYo 0I7Svxi5V6H31+9XJsNXYoa/XfCMyiUT/Cx7VYR7TDi6uJy9th/wdYclGeS7YwIbLt ixr2W+eV3gPLu8OWpnmP0AYPLBslZhiXeOUWatOE= Date: Mon, 12 Feb 2024 16:33:22 -0800 To: mm-commits@vger.kernel.org,willy@infradead.org,timmurray@google.com,surenb@google.com,rppt@kernel.org,peterx@redhat.com,ngeoffray@google.com,Liam.Howlett@oracle.com,kaleshsingh@google.com,jannh@google.com,david@redhat.com,bgeffon@google.com,axelrasmussen@google.com,aarcange@redhat.com,lokeshgidra@google.com,akpm@linux-foundation.org From: Andrew Morton Subject: + userfaultfd-move-userfaultfd_ctx-struct-to-header-file.patch added to mm-unstable branch Message-Id: <20240213003323.508EBC433C7@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: userfaultfd: move userfaultfd_ctx struct to header file has been added to the -mm mm-unstable branch. Its filename is userfaultfd-move-userfaultfd_ctx-struct-to-header-file.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/userfaultfd-move-userfaultfd_ctx-struct-to-header-file.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: Lokesh Gidra Subject: userfaultfd: move userfaultfd_ctx struct to header file Date: Mon, 12 Feb 2024 16:19:18 -0800 Patch series "per-vma locks in userfaultfd", v5. Performing userfaultfd operations (like copy/move etc.) in critical section of mmap_lock (read-mode) causes significant contention on the lock when operations requiring the lock in write-mode are taking place concurrently. We can use per-vma locks instead to significantly reduce the contention issue. Android runtime's Garbage Collector uses userfaultfd for concurrent compaction. mmap-lock contention during compaction potentially causes jittery experience for the user. During one such reproducible scenario, we observed the following improvements with this patch-set: - Wall clock time of compaction phase came down from ~3s to <500ms - Uninterruptible sleep time (across all threads in the process) was ~10ms (none in mmap_lock) during compaction, instead of >20s This patch (of 5): Moving the struct to userfaultfd_k.h to be accessible from mm/userfaultfd.c. There are no other changes in the struct. This is required to prepare for using per-vma locks in userfaultfd operations. Link: https://lkml.kernel.org/r/20240213001920.3551772-1-lokeshgidra@google.com Link: https://lkml.kernel.org/r/20240213001920.3551772-2-lokeshgidra@google.com Signed-off-by: Lokesh Gidra Reviewed-by: Mike Rapoport (IBM) Cc: Andrea Arcangeli Cc: Axel Rasmussen Cc: Brian Geffon Cc: David Hildenbrand Cc: Jann Horn Cc: Kalesh Singh Cc: Liam R. Howlett Cc: Matthew Wilcox (Oracle) Cc: Nicolas Geoffray Cc: Peter Xu Cc: Suren Baghdasaryan Cc: Tim Murray Signed-off-by: Andrew Morton --- fs/userfaultfd.c | 39 -------------------------------- include/linux/userfaultfd_k.h | 39 ++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+), 39 deletions(-) --- a/fs/userfaultfd.c~userfaultfd-move-userfaultfd_ctx-struct-to-header-file +++ a/fs/userfaultfd.c @@ -50,45 +50,6 @@ static struct ctl_table vm_userfaultfd_t static struct kmem_cache *userfaultfd_ctx_cachep __ro_after_init; -/* - * Start with fault_pending_wqh and fault_wqh so they're more likely - * to be in the same cacheline. - * - * Locking order: - * fd_wqh.lock - * fault_pending_wqh.lock - * fault_wqh.lock - * event_wqh.lock - * - * To avoid deadlocks, IRQs must be disabled when taking any of the above locks, - * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's - * also taken in IRQ context. - */ -struct userfaultfd_ctx { - /* waitqueue head for the pending (i.e. not read) userfaults */ - wait_queue_head_t fault_pending_wqh; - /* waitqueue head for the userfaults */ - wait_queue_head_t fault_wqh; - /* waitqueue head for the pseudo fd to wakeup poll/read */ - wait_queue_head_t fd_wqh; - /* waitqueue head for events */ - wait_queue_head_t event_wqh; - /* a refile sequence protected by fault_pending_wqh lock */ - seqcount_spinlock_t refile_seq; - /* pseudo fd refcounting */ - refcount_t refcount; - /* userfaultfd syscall flags */ - unsigned int flags; - /* features requested from the userspace */ - unsigned int features; - /* released */ - bool released; - /* memory mappings are changing because of non-cooperative event */ - atomic_t mmap_changing; - /* mm with one ore more vmas attached to this userfaultfd_ctx */ - struct mm_struct *mm; -}; - struct userfaultfd_fork_ctx { struct userfaultfd_ctx *orig; struct userfaultfd_ctx *new; --- a/include/linux/userfaultfd_k.h~userfaultfd-move-userfaultfd_ctx-struct-to-header-file +++ a/include/linux/userfaultfd_k.h @@ -36,6 +36,45 @@ #define UFFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK) #define UFFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS) +/* + * Start with fault_pending_wqh and fault_wqh so they're more likely + * to be in the same cacheline. + * + * Locking order: + * fd_wqh.lock + * fault_pending_wqh.lock + * fault_wqh.lock + * event_wqh.lock + * + * To avoid deadlocks, IRQs must be disabled when taking any of the above locks, + * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's + * also taken in IRQ context. + */ +struct userfaultfd_ctx { + /* waitqueue head for the pending (i.e. not read) userfaults */ + wait_queue_head_t fault_pending_wqh; + /* waitqueue head for the userfaults */ + wait_queue_head_t fault_wqh; + /* waitqueue head for the pseudo fd to wakeup poll/read */ + wait_queue_head_t fd_wqh; + /* waitqueue head for events */ + wait_queue_head_t event_wqh; + /* a refile sequence protected by fault_pending_wqh lock */ + seqcount_spinlock_t refile_seq; + /* pseudo fd refcounting */ + refcount_t refcount; + /* userfaultfd syscall flags */ + unsigned int flags; + /* features requested from the userspace */ + unsigned int features; + /* released */ + bool released; + /* memory mappings are changing because of non-cooperative event */ + atomic_t mmap_changing; + /* mm with one ore more vmas attached to this userfaultfd_ctx */ + struct mm_struct *mm; +}; + extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason); /* A combined operation mode + behavior flags. */ _ Patches currently in -mm which might be from lokeshgidra@google.com are userfaultfd-fix-return-error-if-mmap_changing-is-non-zero-in-move-ioctl.patch userfaultfd-move-userfaultfd_ctx-struct-to-header-file.patch userfaultfd-protect-mmap_changing-with-rw_sem-in-userfaulfd_ctx.patch userfaultfd-use-per-vma-locks-in-userfaultfd-operations.patch