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Message-ID: <d27f22f0-0f1e-e1bb-5b13-a524dc6e94d7@salutedevices.com> Date: Tue, 12 Dec 2023 18:59:03 +0300 From: Arseniy Krasnov <avkrasnov@...utedevices.com> To: "Michael S. Tsirkin" <mst@...hat.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 12.12.2023 18:54, Michael S. Tsirkin wrote: > 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> Thanks! > > > But I worry whether we actually need 3/8 in net not in net-next. Because of "Fixes" tag ? I think this problem is not critical and reproducible only in special cases, but i'm not familiar with netdev process so good, so I don't have strong opinion. I guess @Stefano knows better. Thanks, Arseniy > > 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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