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[79.46.200.222]) by smtp.gmail.com with ESMTPSA id w12-20020ac843cc000000b0035bb6c3811asm4780775qtn.53.2022.09.29.00.46.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Sep 2022 00:46:16 -0700 (PDT) Date: Thu, 29 Sep 2022 09:46:06 +0200 From: Stefano Garzarella To: "Michael S. Tsirkin" Cc: Junichi Uekawa =?utf-8?B?KOS4iuW3nee0lOS4gCk=?= , Stefan Hajnoczi , Jason Wang , Eric Dumazet , davem@davemloft.net, netdev@vger.kernel.org, Jakub Kicinski , virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, Paolo Abeni , linux-kernel@vger.kernel.org, Bobby Eshleman Subject: Re: [PATCH] vhost/vsock: Use kvmalloc/kvfree for larger packets. Message-ID: <20220929074606.yqzihpcc7cl442c5@sgarzare-redhat> References: <20220928064538.667678-1-uekawa@chromium.org> <20220928082823.wyxplop5wtpuurwo@sgarzare-redhat> <20220928052738-mutt-send-email-mst@kernel.org> <20220928151135.pvrlsylg6j3hzh74@sgarzare-redhat> <20220929031419-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220929031419-mutt-send-email-mst@kernel.org> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Sep 29, 2022 at 03:19:14AM -0400, Michael S. Tsirkin wrote: >On Thu, Sep 29, 2022 at 08:14:24AM +0900, Junichi Uekawa (上川純一) wrote: >> 2022年9月29日(木) 0:11 Stefano Garzarella : >> > >> > On Wed, Sep 28, 2022 at 05:31:58AM -0400, Michael S. Tsirkin wrote: >> > >On Wed, Sep 28, 2022 at 10:28:23AM +0200, Stefano Garzarella wrote: >> > >> On Wed, Sep 28, 2022 at 03:45:38PM +0900, Junichi Uekawa wrote: >> > >> > When copying a large file over sftp over vsock, data size is usually 32kB, >> > >> > and kmalloc seems to fail to try to allocate 32 32kB regions. >> > >> > >> > >> > Call Trace: >> > >> > [] dump_stack+0x97/0xdb >> > >> > [] warn_alloc_failed+0x10f/0x138 >> > >> > [] ? __alloc_pages_direct_compact+0x38/0xc8 >> > >> > [] __alloc_pages_nodemask+0x84c/0x90d >> > >> > [] alloc_kmem_pages+0x17/0x19 >> > >> > [] kmalloc_order_trace+0x2b/0xdb >> > >> > [] __kmalloc+0x177/0x1f7 >> > >> > [] ? copy_from_iter+0x8d/0x31d >> > >> > [] vhost_vsock_handle_tx_kick+0x1fa/0x301 [vhost_vsock] >> > >> > [] vhost_worker+0xf7/0x157 [vhost] >> > >> > [] kthread+0xfd/0x105 >> > >> > [] ? vhost_dev_set_owner+0x22e/0x22e [vhost] >> > >> > [] ? flush_kthread_worker+0xf3/0xf3 >> > >> > [] ret_from_fork+0x4e/0x80 >> > >> > [] ? flush_kthread_worker+0xf3/0xf3 >> > >> > >> > >> > Work around by doing kvmalloc instead. >> > >> > >> > >> > Signed-off-by: Junichi Uekawa >> > > >> > >My worry here is that this in more of a work around. >> > >It would be better to not allocate memory so aggressively: >> > >if we are so short on memory we should probably process >> > >packets one at a time. Is that very hard to implement? >> > >> > Currently the "virtio_vsock_pkt" is allocated in the "handle_kick" >> > callback of TX virtqueue. Then the packet is multiplexed on the right >> > socket queue, then the user space can de-queue it whenever they want. >> > >> > So maybe we can stop processing the virtqueue if we are short on memory, >> > but when can we restart the TX virtqueue processing? >> > >> > I think as long as the guest used only 4K buffers we had no problem, but >> > now that it can create larger buffers the host may not be able to >> > allocate it contiguously. Since there is no need to have them contiguous >> > here, I think this patch is okay. >> > >> > However, if we switch to sk_buff (as Bobby is already doing), maybe we >> > don't have this problem because I think there is some kind of >> > pre-allocated pool. >> > >> >> Thank you for the review! I was wondering if this is a reasonable workaround (as >> we found that this patch makes a reliably crashing system into a >> reliably surviving system.) >> >> >> ... Sounds like it is a reasonable patch to use backported to older kernels? > >Hmm. Good point about stable. OK. Right, so in this case I think is better to add a Fixes tag. Since we used kmalloc from the beginning we can use the following: Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") > >Acked-by: Michael S. Tsirkin > @Michael are you queueing this, or should it go through net tree? Thanks, Stefano