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Tsirkin" To: Stefano Garzarella 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: <20220929034807-mutt-send-email-mst@kernel.org> 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> <20220929074606.yqzihpcc7cl442c5@sgarzare-redhat> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220929074606.yqzihpcc7cl442c5@sgarzare-redhat> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Sep 29, 2022 at 09:46:06AM +0200, Stefano Garzarella wrote: > 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 net tree would be preferable, my pull for this release is kind of ready ... kuba? -- MST