From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 C3B0F1F03C8 for ; Mon, 20 Jan 2025 18:59:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737399601; cv=none; b=LO/WRVefq8r61nGn819FY2uTPCAfgnzg71/xdAiqsaQW6D1fifeY2OPaWCYRSIJlVjkl/feV5v182tv91uA2qAyinc7ekivKtjD/CHpF7L4t2/eRLt2tC27owjY+pOENJdiLgzltOfW/GBQgtIMNtGi1KNQWNNpBqJkzfeo/+jg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737399601; c=relaxed/simple; bh=1SBWSBKCXS9fBSErX8/nKVMcvFxCIGDZ2mQxTl7qVJo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sbc4lPY/kVVLVX6iJMZYE4Vq0queNpeMwHtZeefpRCma/2ltcU+ZEjnU6i1tAdFCD3S87OZCquUx/LXWGD3wWOtUKzIdBHxZrFi6jMjGJB40bIgxEJ6Esyb+EmPDq6iLM/J5VS5pDMAGvMWsW00s4BtqBsOqH6VNM25raNTaGsg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=IJiRA7E2; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="IJiRA7E2" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1737399598; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=Pf/+pmtSEcW2J86C8PhnSXcNEKOxqEuzriHaKO+xXPk=; b=IJiRA7E2jyf1zH4fJwVTBT4FQkJHzUpUl/El0FFA4HTWwAgBJbB5ZeZatk4N32uegklcb7 Icw4R8UOydFO3p0T+xnCXvo2QummyGeCts+HmOXgLqacug2M4TIrOARHcIGr55AGvpM6zP T+3wBBq6a0RJN7iP9k8UJCOM5Gyltkk= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-373-U_3lv9ibOMyNtOFX7A1dqQ-1; Mon, 20 Jan 2025 13:59:57 -0500 X-MC-Unique: U_3lv9ibOMyNtOFX7A1dqQ-1 X-Mimecast-MFC-AGG-ID: U_3lv9ibOMyNtOFX7A1dqQ Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-4362b9c15d8so24891735e9.3 for ; Mon, 20 Jan 2025 10:59:56 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1737399596; x=1738004396; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=Pf/+pmtSEcW2J86C8PhnSXcNEKOxqEuzriHaKO+xXPk=; b=TawlIj2o14MdFl6HElBx+zEXW2CDoOLpoeokwkWa8Zwe0kX9efXoRlAaD3UWEe4d85 XdPH2/W+7oNDzpGk9Q2mijXMNZVw43XBnm5E7UqzOEcQx8bFwpFz7roH5p2vNqBoiBTj IIw6r8NSUPWTrhRiDBDAtl6gkCoGpZxgsvRZe7tVQFv7rGwVvAPATF73SrfyRR3ba5qd ciFB3+ZKdGfKDK8YoGOUQsqNbhsLmKLoRNHcRNjvd/yuS8C+JtrCTmKYvV4DxK+MyLXH oYuNUAzzDYEDMr3XRh33iMYz+DfUA8tqUBPdSv7wmDbV+/S2zTLOyGvzhT0nF42hSeIj Ssew== X-Forwarded-Encrypted: i=1; AJvYcCXgrN5h6sEHi6rSW87g9DR+MED+U04DJDVe8uSx06jREEL0q8ItCiQs3X/dq2/nxczwPJp6RjFXPN/fnoY=@vger.kernel.org X-Gm-Message-State: AOJu0Yz8E+fU7Si/hyU4thLYNIN3zC8LDX6vNZCrzWNRlWDWUBA8r99Z Ts8EpyDkUW3tQ2RrXC/KIMj2Ia4lXvfnIq5f4/Dx+aDhefmjNK5s/t3zQ5Jv5EquH8b5TAmJbIG RCVBBZk2fz03E8ZTxKwYLxSYmki92h1iPnnntFkIlyCkdGBx8VXbKfssZCzFmY99DNZzOEw== X-Gm-Gg: ASbGncu7gzGTDMgsuv9KqoyI600n0TpZWvVw0OqwxZWVJvW0QGF7cr3JvI6BKbL7p4s puy3Mx2CpWwoQuTItej0A2YK76hkC5w33qEtVH/U4r3mtycR6yDZaOpBepLwJKOiIyiuABPXZS2 usjBYBuFqSSjlfllwhGeQJI6rSsq+mq3xYgFaCRHEjG5W06HVOIS8lLrBUhDr6AupWPaBw5J2F1 yDWy0zNN2A0PBNh8uIMVZJoE2CjebDyD1VgD7kN30q+LaPPWaCf1YePDUW3k5QVQi0Io21wDdSs qz5Q3oieYjCGQZ5+qOyMvEgMCSH8zBNRwMB0wlaABgL55uq9lZ8TOUVlnu8fbQNQFLj2n0SJJly TQ4Qt+ceOuwovbH55t2ZUHg== X-Received: by 2002:a05:600c:510c:b0:434:a1e7:27b0 with SMTP id 5b1f17b1804b1-438913ccd4amr166011735e9.11.1737399595735; Mon, 20 Jan 2025 10:59:55 -0800 (PST) X-Google-Smtp-Source: AGHT+IH+TPy54/lS3UFFrnmG1O7DZZp3fmFAErUo+YtByu8LHirZNl4hbvPpqLOD+qxS2Tc6vW5HSw== X-Received: by 2002:a05:600c:510c:b0:434:a1e7:27b0 with SMTP id 5b1f17b1804b1-438913ccd4amr166011455e9.11.1737399595303; Mon, 20 Jan 2025 10:59:55 -0800 (PST) Received: from ?IPV6:2003:cb:c72e:e400:431d:9c08:5611:693c? (p200300cbc72ee400431d9c085611693c.dip0.t-ipconnect.de. [2003:cb:c72e:e400:431d:9c08:5611:693c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38bf327decbsm11436866f8f.90.2025.01.20.10.59.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Jan 2025 10:59:54 -0800 (PST) Message-ID: Date: Mon, 20 Jan 2025 19:59:52 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RESEND PATCH] fs: avoid mmap sem relocks when coredumping with many missing pages To: Mateusz Guzik , brauner@kernel.org Cc: viro@zeniv.linux.org.uk, jack@suse.cz, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, tavianator@tavianator.com, linux-mm@kvack.org, akpm@linux-foundation.org References: <20250119103205.2172432-1-mjguzik@gmail.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20250119103205.2172432-1-mjguzik@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 19.01.25 11:32, Mateusz Guzik wrote: > Dumping processes with large allocated and mostly not-faulted areas is > very slow. > > Borrowing a test case from Tavian Barnes: > > int main(void) { > char *mem = mmap(NULL, 1ULL << 40, PROT_READ | PROT_WRITE, > MAP_ANONYMOUS | MAP_NORESERVE | MAP_PRIVATE, -1, 0); > printf("%p %m\n", mem); > if (mem != MAP_FAILED) { > mem[0] = 1; > } > abort(); > } > > That's 1TB of almost completely not-populated area. > > On my test box it takes 13-14 seconds to dump. > > The profile shows: > - 99.89% 0.00% a.out > entry_SYSCALL_64_after_hwframe > do_syscall_64 > syscall_exit_to_user_mode > arch_do_signal_or_restart > - get_signal > - 99.89% do_coredump > - 99.88% elf_core_dump > - dump_user_range > - 98.12% get_dump_page > - 64.19% __get_user_pages > - 40.92% gup_vma_lookup > - find_vma > - mt_find > 4.21% __rcu_read_lock > 1.33% __rcu_read_unlock > - 3.14% check_vma_flags > 0.68% vma_is_secretmem > 0.61% __cond_resched > 0.60% vma_pgtable_walk_end > 0.59% vma_pgtable_walk_begin > 0.58% no_page_table > - 15.13% down_read_killable > 0.69% __cond_resched > 13.84% up_read > 0.58% __cond_resched > > Almost 29% of the time is spent relocking the mmap semaphore between > calls to get_dump_page() which find nothing. > > Whacking that results in times of 10 seconds (down from 13-14). > > While here make the thing killable. > > The real problem is the page-sized iteration and the real fix would > patch it up instead. It is left as an exercise for the mm-familiar > reader. > > Signed-off-by: Mateusz Guzik > --- > > Minimally tested, very plausible I missed something. > > sent again because the previous thing has myself in To -- i failed to > fix up the oneliner suggested by lore.kernel.org. it seem the original > got lost. > > arch/arm64/kernel/elfcore.c | 3 ++- > fs/coredump.c | 38 +++++++++++++++++++++++++++++++------ > include/linux/mm.h | 2 +- > mm/gup.c | 5 ++--- > 4 files changed, 37 insertions(+), 11 deletions(-) > MM side LGTM Acked-by: David Hildenbrand -- Cheers, David / dhildenb