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Date: Tue, 12 Dec 2023 10:54:50 -0500 From: "Michael S. Tsirkin" <mst@...hat.com> To: Arseniy Krasnov <avkrasnov@...utedevices.com> Cc: Stefan Hajnoczi <stefanha@...hat.com>, Stefano Garzarella <sgarzare@...hat.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Jason Wang <jasowang@...hat.com>, Bobby Eshleman <bobby.eshleman@...edance.com>, kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, kernel@...rdevices.ru, oxffffaa@...il.com Subject: Re: [PATCH net-next v8 0/4] send credit update during setting SO_RCVLOWAT On Tue, Dec 12, 2023 at 12:16:54AM +0300, Arseniy Krasnov wrote: > Hello, > > DESCRIPTION > > This patchset fixes old problem with hungup of both rx/tx sides and adds > test for it. This happens due to non-default SO_RCVLOWAT value and > deferred credit update in virtio/vsock. Link to previous old patchset: > https://lore.kernel.org/netdev/39b2e9fd-601b-189d-39a9-914e5574524c@sberdevices.ru/ Patchset: Acked-by: Michael S. Tsirkin <mst@...hat.com> But I worry whether we actually need 3/8 in net not in net-next. Thanks! > Here is what happens step by step: > > TEST > > INITIAL CONDITIONS > > 1) Vsock buffer size is 128KB. > 2) Maximum packet size is also 64KB as defined in header (yes it is > hardcoded, just to remind about that value). > 3) SO_RCVLOWAT is default, e.g. 1 byte. > > > STEPS > > SENDER RECEIVER > 1) sends 128KB + 1 byte in a > single buffer. 128KB will > be sent, but for 1 byte > sender will wait for free > space at peer. Sender goes > to sleep. > > > 2) reads 64KB, credit update not sent > 3) sets SO_RCVLOWAT to 64KB + 1 > 4) poll() -> wait forever, there is > only 64KB available to read. > > So in step 4) receiver also goes to sleep, waiting for enough data or > connection shutdown message from the sender. Idea to fix it is that rx > kicks tx side to continue transmission (and may be close connection) > when rx changes number of bytes to be woken up (e.g. SO_RCVLOWAT) and > this value is bigger than number of available bytes to read. > > I've added small test for this, but not sure as it uses hardcoded value > for maximum packet length, this value is defined in kernel header and > used to control deferred credit update. And as this is not available to > userspace, I can't control test parameters correctly (if one day this > define will be changed - test may become useless). > > Head for this patchset is: > https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=021b0c952f226236f2edf89c737efb9a28d1422d > > Link to v1: > https://lore.kernel.org/netdev/20231108072004.1045669-1-avkrasnov@salutedevices.com/ > Link to v2: > https://lore.kernel.org/netdev/20231119204922.2251912-1-avkrasnov@salutedevices.com/ > Link to v3: > https://lore.kernel.org/netdev/20231122180510.2297075-1-avkrasnov@salutedevices.com/ > Link to v4: > https://lore.kernel.org/netdev/20231129212519.2938875-1-avkrasnov@salutedevices.com/ > Link to v5: > https://lore.kernel.org/netdev/20231130130840.253733-1-avkrasnov@salutedevices.com/ > Link to v6: > https://lore.kernel.org/netdev/20231205064806.2851305-1-avkrasnov@salutedevices.com/ > Link to v7: > https://lore.kernel.org/netdev/20231206211849.2707151-1-avkrasnov@salutedevices.com/ > > Changelog: > v1 -> v2: > * Patchset rebased and tested on new HEAD of net-next (see hash above). > * New patch is added as 0001 - it removes return from SO_RCVLOWAT set > callback in 'af_vsock.c' when transport callback is set - with that > we can set 'sk_rcvlowat' only once in 'af_vsock.c' and in future do > not copy-paste it to every transport. It was discussed in v1. > * See per-patch changelog after ---. > v2 -> v3: > * See changelog after --- in 0003 only (0001 and 0002 still same). > v3 -> v4: > * Patchset rebased and tested on new HEAD of net-next (see hash above). > * See per-patch changelog after ---. > v4 -> v5: > * Change patchset tag 'RFC' -> 'net-next'. > * See per-patch changelog after ---. > v5 -> v6: > * New patch 0003 which sends credit update during reading bytes from > socket. > * See per-patch changelog after ---. > v6 -> v7: > * Patchset rebased and tested on new HEAD of net-next (see hash above). > * See per-patch changelog after ---. > v7 -> v8: > * See per-patch changelog after ---. > > Arseniy Krasnov (4): > vsock: update SO_RCVLOWAT setting callback > virtio/vsock: send credit update during setting SO_RCVLOWAT > virtio/vsock: fix logic which reduces credit update messages > vsock/test: two tests to check credit update logic > > drivers/vhost/vsock.c | 1 + > include/linux/virtio_vsock.h | 1 + > include/net/af_vsock.h | 2 +- > net/vmw_vsock/af_vsock.c | 9 +- > net/vmw_vsock/hyperv_transport.c | 4 +- > net/vmw_vsock/virtio_transport.c | 1 + > net/vmw_vsock/virtio_transport_common.c | 43 +++++- > net/vmw_vsock/vsock_loopback.c | 1 + > tools/testing/vsock/vsock_test.c | 175 ++++++++++++++++++++++++ > 9 files changed, 229 insertions(+), 8 deletions(-) > > -- > 2.25.1
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