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 19B7AC433F5 for ; Thu, 24 Mar 2022 23:42:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231378AbiCXXoI (ORCPT ); Thu, 24 Mar 2022 19:44:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49072 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356422AbiCXXnB (ORCPT ); Thu, 24 Mar 2022 19:43:01 -0400 Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F2AB3BA31C for ; Thu, 24 Mar 2022 16:41:27 -0700 (PDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-2e5bcae3665so47681817b3.16 for ; Thu, 24 Mar 2022 16:41:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=YM5HWwtsuon+nq2pjNDv8Dl1s4yCw5MepRNvjajdRw8=; b=B+BmeYhFUl732dOfJ3g/AH0DUva74mBYCMxNYvLXJmUf3f3DsoL8nrpaQnli+1YQVz 5WPtDROMaecvyIqMTYigAL9o6AiMZI6EPdXxBi04Hmpjmu4/PIkNfRi3FLCE0afTj2KJ Z4hMpnUrglfvmrCGGh+Za6gJ3gkGaQEXmcH+lIboOCX+uxSXopXcOoR8ARexTDcNygmD ZEPsPg6vBK60p4AXrTn9EbpUx1D3+mG2ZoigPFAQqVrWvMtYVTYWPnAOnt/eVb4/BokG vZmHhLqv3FPdcV2W0BD6D9RSE2csfCyAHSHvQLotBn1aIVhhKzfP3UWE34NB2sCHSdDn R4SQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=YM5HWwtsuon+nq2pjNDv8Dl1s4yCw5MepRNvjajdRw8=; b=vHkeQKNxIwLZEXc/3ZxXs6liW/SeYGDTa9yDBvq3ZmAKy7cdUFICCbhBwNtKbrL+uk T2/JpkVrB9oaA1WJnZF8h8n2tktvUjUmbXatr0sCz91RoFphqlv00kJPoTchZ74xWX0f v9TO+7BEqCKD1aTiofIK4Cy0XfXLnMeL4FIffVuIAgUcvTp+3qmZ20GEEdUR3Y+y16s6 B0urqJeh94W9eH7ZkxOh+ICDZtVUPbXTXqMZ0baxJEWzQ5h5e28qKeYXCpkwa98Vm3qC /oaVmWu6ZDpoL5d4ZuufDdMhkalneQ9p+quw2RUUUQdZRna4ybigqUVbT3UlVQhJjUPN H6KA== X-Gm-Message-State: AOAM533DYcv5FtlbsQrXmsGSYDhsAYQYYqjjZ1i0r9hIVVPuxMcNUptl wEOaV16raM/P4t6ujrpjHSnCaMQivI8= X-Google-Smtp-Source: ABdhPJyHyZ2WgjGriCBsdHXAi1Do5BWOgO1m6A0z6NLZii0z+HW4WqZQi+VdPnE4P9A//WlpZMKlDtuZSEs= X-Received: from haoluo.svl.corp.google.com ([2620:15c:2cd:202:f3eb:bf7b:2da4:12c9]) (user=haoluo job=sendgmr) by 2002:a81:1bc3:0:b0:2e3:aa1:f553 with SMTP id b186-20020a811bc3000000b002e30aa1f553mr7547386ywb.491.1648165287205; Thu, 24 Mar 2022 16:41:27 -0700 (PDT) Date: Thu, 24 Mar 2022 16:41:21 -0700 Message-Id: <20220324234123.1608337-1-haoluo@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.35.1.1021.g381101b075-goog Subject: [PATCH RFC bpf-next 0/2] Mmapable task local storage. From: Hao Luo To: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann Cc: yhs@fb.com, KP Singh , Martin KaFai Lau , Song Liu , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Hao Luo Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Some map types support mmap operation, which allows userspace to communicate with BPF programs directly. Currently only arraymap and ringbuf have mmap implemented. However, in some use cases, when multiple program instances can run concurrently, global mmapable memory can cause race. In that case, userspace needs to provide necessary synchronizations to coordinate the usage of mapped global data. This can be a source of bottleneck. It would be great to have a mmapable local storage in that case. This patch adds that. Mmap isn't BPF syscall, so unpriv users can also use it to interact with maps. Currently the only way of allocating mmapable map area is using vmalloc() and it's only used at map allocation time. Vmalloc() may sleep, therefore it's not suitable for maps that may allocate memory in an atomic context such as local storage. Local storage uses kmalloc() with GFP_ATOMIC, which doesn't sleep. This patch uses kmalloc() with GFP_ATOMIC as well for mmapable map area. Allocating mmapable memory has requirment on page alignment. So we have to deliberately allocate more memory than necessary to obtain an address that has sdata->data aligned at page boundary. The calculations for mmapable allocation size, and the actual allocation/deallocation are packaged in three functions: - bpf_map_mmapable_alloc_size() - bpf_map_mmapable_kzalloc() - bpf_map_mmapable_kfree() BPF local storage uses them to provide generic mmap API: - bpf_local_storage_mmap() And task local storage adds the mmap callback: - task_storage_map_mmap() When application calls mmap on a task local storage, it gets its own local storage. Overall, mmapable local storage trades off memory with flexibility and efficiency. It brings memory fragmentation but can make programs stateless. Therefore useful in some cases. Hao Luo (2): bpf: Mmapable local storage. selftests/bpf: Test mmapable task local storage. include/linux/bpf.h | 4 + include/linux/bpf_local_storage.h | 5 +- kernel/bpf/bpf_local_storage.c | 73 +++++++++++++++++-- kernel/bpf/bpf_task_storage.c | 40 ++++++++++ kernel/bpf/syscall.c | 67 +++++++++++++++++ .../bpf/prog_tests/task_local_storage.c | 38 ++++++++++ .../bpf/progs/task_local_storage_mmapable.c | 38 ++++++++++ 7 files changed, 257 insertions(+), 8 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/task_local_storage_mmapable.c -- 2.35.1.1021.g381101b075-goog