netdev - Re: [PATCH net-next] sock: add sndbuff full perf trace event

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Message-ID: <CALALjgzLSmv4yiSuiF0DLU717peuhV3B1UAZ3uc9XStny4LR9w@mail.gmail.com>
Date:   Tue, 25 Jan 2022 11:51:41 -0800
From:   Joe Damato <jdamato@...tly.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org
Subject: Re: [PATCH net-next] sock: add sndbuff full perf trace event

 On Sun, Jan 23, 2022 at 12:17 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> On Thu, Jan 20, 2022 at 02:02:30PM -0800, Joe Damato wrote:
> > Calls to sock_alloc_send_pskb can fail or trigger a wait if there is no
> > sndbuf space available.
> >
> > Add a perf trace event to help users monitor when and how this occurs so
> > appropriate application level changes can be made, if necessary.
> >
> > Signed-off-by: Joe Damato <jdamato@...tly.com>
> > ---
> >  include/trace/events/sock.h | 21 +++++++++++++++++++++
> >  net/core/sock.c             |  1 +
> >  2 files changed, 22 insertions(+)
>
> There are more places where we set the SOCKWQ_ASYNC_NOSPACE bit, so
> it looks like your patch is incomplete.

Thanks for taking a look.

I had originally taken your comment to suggest that the generic stream
code should trigger the same tracepoint; I agree and am happy to
generate a v2 with that case covered.

Are you suggesting that all places where SOCKWQ_ASYNC_NOSPACE is set
(e.g. the poll functions for various protocols) should trigger this
tracepoint, as well? Some of these may not have a user configurable
sndbuf, but I suppose knowing that this event is happening could be
helpful.

Thanks.