From: Andrea Arcangeli <aarcange@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
qemu-devel@nongnu.org, kvm@vger.kernel.org,
linux-api@vger.kernel.org, Pavel Emelyanov <xemul@parallels.com>,
Sanidhya Kashyap <sanidhya.gatech@gmail.com>,
zhang.zhanghailiang@huawei.com,
Linus Torvalds <torvalds@linux-foundation.org>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Andres Lagar-Cavilla <andreslc@google.com>,
Dave Hansen <dave.hansen@intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Rik van Riel <riel@redhat.com>, Mel Gorman <mgorman@suse.de>,
Andy Lutomirski <luto@amacapital.net>,
Hugh Dickins <hughd@google.com>,
Peter Feiner <pfeiner@google.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
"Huangpeng (Peter)" <peter.huangpeng@huawei.com>
Subject: Re: [PATCH 14/23] userfaultfd: wake pending userfaults
Date: Thu, 22 Oct 2015 17:30:55 +0200 [thread overview]
Message-ID: <20151022153055.GC1331@redhat.com> (raw)
In-Reply-To: <20151022151509.GO3604@twins.programming.kicks-ass.net>
On Thu, Oct 22, 2015 at 05:15:09PM +0200, Peter Zijlstra wrote:
> Indefinitely is such a long time, we should try and finish
> computation before the computer dies etc. :-)
Indefinitely as read_seqcount_retry, eventually it makes progress.
Even returning 0 from the page fault can trigger it again
indefinitely, so VM_FAULT_RETRY isn't fundamentally different from
returning 0 and retrying the page fault again later. So it's not clear
why VM_FAULT_RETRY can only try once more.
FAULT_FLAG_TRIED as a message to the VM so it starts to do heavy
locking and block more aggressively is actually useful as such, but it
shouldn't be a replacement of FAULT_FLAG_ALLOW_RETRY. What I meant
with removing FAULT_FLAG_TRIED is really about converting it to an
hint, but not controlling if the page fault can keep retrying
in-kernel.
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next prev parent reply other threads:[~2015-10-22 15:31 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-14 17:30 [PATCH 00/23] userfaultfd v4 Andrea Arcangeli
2015-05-14 17:30 ` [PATCH 01/23] userfaultfd: linux/Documentation/vm/userfaultfd.txt Andrea Arcangeli
2015-09-11 8:47 ` Michael Kerrisk (man-pages)
2015-12-04 15:50 ` Michael Kerrisk (man-pages)
2015-12-04 17:55 ` Andrea Arcangeli
2015-05-14 17:30 ` [PATCH 02/23] userfaultfd: waitqueue: add nr wake parameter to __wake_up_locked_key Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 03/23] userfaultfd: uAPI Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 04/23] userfaultfd: linux/userfaultfd_k.h Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 05/23] userfaultfd: add vm_userfaultfd_ctx to the vm_area_struct Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 06/23] userfaultfd: add VM_UFFD_MISSING and VM_UFFD_WP Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 07/23] userfaultfd: call handle_userfault() for userfaultfd_missing() faults Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 08/23] userfaultfd: teach vma_merge to merge across vma->vm_userfaultfd_ctx Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 09/23] userfaultfd: prevent khugepaged to merge if userfaultfd is armed Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 10/23] userfaultfd: add new syscall to provide memory externalization Andrea Arcangeli
2015-05-14 17:49 ` Linus Torvalds
2015-05-15 16:04 ` Andrea Arcangeli
2015-05-15 18:22 ` Linus Torvalds
2015-06-23 19:00 ` Dave Hansen
2015-06-23 21:41 ` Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 11/23] userfaultfd: Rename uffd_api.bits into .features Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 12/23] userfaultfd: Rename uffd_api.bits into .features fixup Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 13/23] userfaultfd: change the read API to return a uffd_msg Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 14/23] userfaultfd: wake pending userfaults Andrea Arcangeli
2015-10-22 12:10 ` Peter Zijlstra
2015-10-22 13:20 ` Andrea Arcangeli
2015-10-22 13:38 ` Peter Zijlstra
2015-10-22 14:18 ` Andrea Arcangeli
2015-10-22 15:15 ` Peter Zijlstra
2015-10-22 15:30 ` Andrea Arcangeli [this message]
2015-05-14 17:31 ` [PATCH 15/23] userfaultfd: optimize read() and poll() to be O(1) Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 16/23] userfaultfd: allocate the userfaultfd_ctx cacheline aligned Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 17/23] userfaultfd: solve the race between UFFDIO_COPY|ZEROPAGE and read Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 18/23] userfaultfd: buildsystem activation Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 19/23] userfaultfd: activate syscall Andrea Arcangeli
2015-08-11 10:07 ` [Qemu-devel] " Bharata B Rao
2015-08-11 13:48 ` Andrea Arcangeli
2015-08-12 5:23 ` Bharata B Rao
2015-09-08 6:08 ` Michael Ellerman
2015-09-08 6:39 ` Bharata B Rao
2015-09-08 7:14 ` Michael Ellerman
2015-09-08 10:40 ` Michael Ellerman
2015-09-08 12:28 ` Dr. David Alan Gilbert
2015-09-08 8:59 ` Dr. David Alan Gilbert
2015-09-08 10:00 ` Bharata B Rao
2015-09-08 12:46 ` Dr. David Alan Gilbert
2015-09-08 13:37 ` Bharata B Rao
2015-09-08 14:13 ` Dr. David Alan Gilbert
2015-05-14 17:31 ` [PATCH 20/23] userfaultfd: UFFDIO_COPY|UFFDIO_ZEROPAGE uAPI Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 21/23] userfaultfd: mcopy_atomic|mfill_zeropage: UFFDIO_COPY|UFFDIO_ZEROPAGE preparation Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 22/23] userfaultfd: avoid mmap_sem read recursion in mcopy_atomic Andrea Arcangeli
2015-05-22 20:18 ` Andrew Morton
2015-05-22 20:48 ` Andrea Arcangeli
2015-05-22 21:18 ` Andrew Morton
2015-05-23 1:04 ` Andrea Arcangeli
2015-05-14 17:31 ` [PATCH 23/23] userfaultfd: UFFDIO_COPY and UFFDIO_ZEROPAGE Andrea Arcangeli
2015-05-18 14:24 ` [PATCH 00/23] userfaultfd v4 Pavel Emelyanov
2015-05-19 21:38 ` Andrew Morton
2015-05-19 21:59 ` Richard Weinberger
2015-05-20 14:17 ` Andrea Arcangeli
2015-05-20 13:23 ` Andrea Arcangeli
2015-05-21 13:11 ` Kirill Smelkov
2015-05-21 15:52 ` Andrea Arcangeli
2015-05-22 16:35 ` Kirill Smelkov
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