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 C1206C28D13 for ; Tue, 23 Aug 2022 02:57:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236382AbiHWC5X (ORCPT ); Mon, 22 Aug 2022 22:57:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49536 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235382AbiHWC5W (ORCPT ); Mon, 22 Aug 2022 22:57:22 -0400 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E1B05A824 for ; Mon, 22 Aug 2022 19:57:21 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.143]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4MBYkp1HXHz6T6XG for ; Tue, 23 Aug 2022 10:55:46 +0800 (CST) Received: from [10.174.176.117] (unknown [10.174.176.117]) by APP2 (Coremail) with SMTP id Syh0CgDn0b0MQgRjK97lAg--.59798S2; Tue, 23 Aug 2022 10:57:19 +0800 (CST) Subject: Re: [PATCH 1/3] bpf: Disable preemption when increasing per-cpu map_locked To: Alexei Starovoitov , Hao Luo Cc: bpf , Song Liu , Hao Sun , Sebastian Andrzej Siewior , Andrii Nakryiko , Yonghong Song , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , KP Singh , "David S . Miller" , Jakub Kicinski , Stanislav Fomichev , Jiri Olsa , John Fastabend , Lorenz Bauer , Hou Tao References: <20220821033223.2598791-1-houtao@huaweicloud.com> <20220821033223.2598791-2-houtao@huaweicloud.com> <3287b95c-30e1-5647-fe2c-1feff673291d@huaweicloud.com> <387c851f-03ae-9b34-4ec0-9667fb26ec18@huaweicloud.com> From: Hou Tao Message-ID: <67c5da0b-e5af-0934-6e17-1c43d0f96165@huaweicloud.com> Date: Tue, 23 Aug 2022 10:57:16 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-CM-TRANSID: Syh0CgDn0b0MQgRjK97lAg--.59798S2 X-Coremail-Antispam: 1UD129KBjvJXoW7ur4xGw4UJrykCF17Cw18Grg_yoW8JF43pa 98Ww4vyF4kXFnFy3ZrWw18W34vva1rKryftrW5GrWDAry5Xr9a9ws2q3W5uFykJFyrKFZa qF4DXF95ZF10va7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUv2b4IE77IF4wAFF20E14v26ryj6rWUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6r1S6rWUM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUGVWUXwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JM4IIrI8v6xkF7I0E8cxan2IY04v7Mxk0xIA0c2IE e2xFo4CEbIxvr21l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxV Aqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r4a 6rW5MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6x kF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVW3JVWrJr1lIxAIcVC2z280aVAF wI0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa 7IUbG2NtUUUUU== X-CM-SenderInfo: xkrx3t3r6k3tpzhluzxrxghudrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Hi, On 8/23/2022 9:29 AM, Alexei Starovoitov wrote: > On Mon, Aug 22, 2022 at 5:56 PM Hao Luo wrote: >> SNIP >> Tao, thanks very much for the test. I played it a bit and I can >> confirm that map_update failures are seen under CONFIG_PREEMPT. The >> failures are not present under CONFIG_PREEMPT_NONE or >> CONFIG_PREEMPT_VOLUNTARY. I experimented with a few alternatives I was >> thinking of and they didn't work. It looks like Hou Tao's idea, >> promoting migrate_disable to preempt_disable, is probably the best we >> can do for the non-RT case. So > preempt_disable is also faster than migrate_disable, > so patch 1 will not only fix this issue, but will improve performance. > > Patch 2 is too hacky though. > I think it's better to wait until my bpf_mem_alloc patches land. > RT case won't be special anymore. We will be able to remove > htab_use_raw_lock() helper and unconditionally use raw_spin_lock. > With bpf_mem_alloc there is no inline memory allocation anymore. OK. Look forwards to the landing of BPF specific memory allocator. > > So please address Hao's comments, add a test and > resubmit patches 1 and 3. > Also please use [PATCH bpf-next] in the subject to help BPF CI > and patchwork scripts. Will do. And to bpf-next instead of bpf ? > .