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[95.203.13.87]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-2ffdfca133asm16501831fa.107.2024.12.03.06.20.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Dec 2024 06:20:06 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 3 Dec 2024 15:20:04 +0100 To: Kefeng Wang Cc: Uladzislau Rezki , zuoze , Matthew Wilcox , gustavoars@kernel.org, akpm@linux-foundation.org, linux-hardening@vger.kernel.org, linux-mm@kvack.org, keescook@chromium.org Subject: Re: [PATCH -next] mm: usercopy: add a debugfs interface to bypass the vmalloc check. Message-ID: References: <20241203023159.219355-1-zuoze1@huawei.com> <57f9eca2-effc-3a9f-932b-fd37ae6d0f87@huawei.com> <92768fc4-4fe0-f74a-d61c-dde0eb64e2c0@huawei.com> <76995749-1c2e-4f78-9aac-a4bff4b8097f@huawei.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Dec 03, 2024 at 10:10:26PM +0800, Kefeng Wang wrote: > > > On 2024/12/3 21:51, Uladzislau Rezki wrote: > > On Tue, Dec 03, 2024 at 09:45:09PM +0800, Kefeng Wang wrote: > > > > > > > > > On 2024/12/3 21:39, Uladzislau Rezki wrote: > > > > On Tue, Dec 03, 2024 at 09:30:09PM +0800, Kefeng Wang wrote: > > > > > > > > > > > > > > > On 2024/12/3 21:10, zuoze wrote: > > > > > > > > > > > > > > > > > > 在 2024/12/3 20:39, Uladzislau Rezki 写道: > > > > > > > On Tue, Dec 03, 2024 at 07:23:44PM +0800, zuoze wrote: > > > > > > > > We have implemented host-guest communication based on the TUN device > > > > > > > > using XSK[1]. The hardware is a Kunpeng 920 machine (ARM architecture), > > > > > > > > and the operating system is based on the 6.6 LTS version with kernel > > > > > > > > version 6.6. The specific stack for hotspot collection is as follows: > > > > > > > > > > > > > > > > -  100.00%     0.00%  vhost-12384  [unknown]      [k] 0000000000000000 > > > > > > > >     - ret_from_fork > > > > > > > >        - 99.99% vhost_task_fn > > > > > > > >           - 99.98% 0xffffdc59f619876c > > > > > > > >              - 98.99% handle_rx_kick > > > > > > > >                 - 98.94% handle_rx > > > > > > > >                    - 94.92% tun_recvmsg > > > > > > > >                       - 94.76% tun_do_read > > > > > > > >                          - 94.62% tun_put_user_xdp_zc > > > > > > > >                             - 63.53% __check_object_size > > > > > > > >                                - 63.49% __check_object_size.part.0 > > > > > > > >                                     find_vmap_area > > > > > > > >                             - 30.02% _copy_to_iter > > > > > > > >                                  __arch_copy_to_user > > > > > > > >                    - 2.27% get_rx_bufs > > > > > > > >                       - 2.12% vhost_get_vq_desc > > > > > > > >                            1.49% __arch_copy_from_user > > > > > > > >                    - 0.89% peek_head_len > > > > > > > >                         0.54% xsk_tx_peek_desc > > > > > > > >                    - 0.68% vhost_add_used_and_signal_n > > > > > > > >                       - 0.53% eventfd_signal > > > > > > > >                            eventfd_signal_mask > > > > > > > >              - 0.94% handle_tx_kick > > > > > > > >                 - 0.94% handle_tx > > > > > > > >                    - handle_tx_copy > > > > > > > >                       - 0.59% vhost_tx_batch.constprop.0 > > > > > > > >                            0.52% tun_sendmsg > > > > > > > > > > > > > > > > It can be observed that most of the overhead is concentrated in the > > > > > > > > find_vmap_area function. > > > > > > > > > ... > > > > > Thank you. Then you have tons of copy_to_iter/copy_from_iter calls > > during your test case. Per each you need to find an area which might > > be really heavy. > > Exactly, no vmalloc check before 0aef499f3172 （"mm/usercopy: Detect vmalloc > overruns"), so no burden in find_vmap_area in old kernel. > Yep. It will slow down for sure. > > > > How many CPUs in a system you have? > > > > 128 core OK. Just in case, do you see in a boot log something like: "Failed to allocate an array. Disable a node layer" Thanks! -- Uladzislau Rezki