netdev - Re: [RFC PATCH v1 2/2] vsock/test: SO_RCVLOWAT + deferred credit update test

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Date: Fri, 17 Nov 2023 09:30:19 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Arseniy Krasnov <avkrasnov@...utedevices.com>
Cc: Stefan Hajnoczi <stefanha@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	"Michael S. Tsirkin" <mst@...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: [RFC PATCH v1 2/2] vsock/test: SO_RCVLOWAT + deferred credit
 update test

On Fri, Nov 17, 2023 at 10:12:38AM +0300, Arseniy Krasnov wrote:
>
>
>On 15.11.2023 14:11, Stefano Garzarella wrote:
>> On Wed, Nov 08, 2023 at 10:20:04AM +0300, Arseniy Krasnov wrote:
>>> This adds test which checks, that updating SO_RCVLOWAT value also sends
>>
>> You can avoid "This adds", and write just "Add test ...".
>>
>> See https://docs.kernel.org/process/submitting-patches.html#describe-your-changes
>>
>>     Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
>>     instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
>>     to do frotz", as if you are giving orders to the codebase to change
>>     its behaviour.
>>
>> Also in the other patch.
>>
>>> credit update message. Otherwise mutual hungup may happen when receiver
>>> didn't send credit update and then calls 'poll()' with non default
>>> SO_RCVLOWAT value (e.g. waiting enough bytes to read), while sender
>>> waits for free space at receiver's side.
>>>
>>> Signed-off-by: Arseniy Krasnov <avkrasnov@...utedevices.com>
>>> ---
>>> tools/testing/vsock/vsock_test.c | 131 +++++++++++++++++++++++++++++++
>>> 1 file changed, 131 insertions(+)
>>>
>>> diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
>>> index c1f7bc9abd22..c71b3875fd16 100644
>>> --- a/tools/testing/vsock/vsock_test.c
>>> +++ b/tools/testing/vsock/vsock_test.c
>>> @@ -1180,6 +1180,132 @@ static void test_stream_shutrd_server(const struct test_opts *opts)
>>>     close(fd);
>>> }
>>>
>>> +#define RCVLOWAT_CREDIT_UPD_BUF_SIZE    (1024 * 128)
>>> +#define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE    (1024 * 64)
>>
>> What about adding a comment like the one in the cover letter about
>> dependency with kernel values?
>>
>> Please add it also in the commit description.
>>
>> I'm thinking if we should move all the defines that depends on the
>> kernel in some special header.
>
>IIUC it will be new header file in tools/testing/vsock, which includes such defines. At
>this moment in will contain only VIRTIO_VSOCK_MAX_PKT_BUF_SIZE. Idea is that such defines

So this only works on the virtio transport though, not the other
transports, right? (but maybe the others don't have this problem, so
it's fine).

>are not supposed to use by user (so do not move it to uapi headers), but needed by tests
>to check kernel behaviour. Please correct me if i'm wrong.

Right!
Maybe if it's just one, we can leave it there for now, but with a
comment on top explaining where it comes.

Thanks,
Stefano