From: Slavomir Kaslev <kaslevs@vmware.com>
To: "rostedt@goodmis.org" <rostedt@goodmis.org>
Cc: "linux-trace-devel@vger.kernel.org" <linux-trace-devel@vger.kernel.org>
Subject: Re: [RFC PATCH v9 11/11] trace-cmd: Add splice() recording from FIFO without additional pipe buffer
Date: Wed, 3 Apr 2019 13:11:07 +0000 [thread overview]
Message-ID: <fe5cbfd1d91e83636d6b32c2522411aed471958d.camel@vmware.com> (raw)
In-Reply-To: <20190403085515.1652201a@gandalf.local.home>
On Wed, 2019-04-03 at 08:55 -0400, Steven Rostedt wrote:
> On Tue, 2 Apr 2019 16:45:40 +0300
> Slavomir Kaslev <kaslevs@vmware.com> wrote:
>
> > +/*
> > + * Returns -1 on error.
> > + * or bytes of data read.
> > + */
> > +static long direct_splice_data(struct tracecmd_recorder *recorder)
> > +{
> > + struct pollfd pfd = {
> > + .fd = recorder->trace_fd,
> > + .events = POLLIN,
> > + };
> > + long read;
> > + int ret;
> > +
> > + ret = poll(&pfd, 1, POLL_TIMEOUT_MS);
> > + if (ret < 0)
> > + return -1;
> > +
> > + if (!(pfd.revents | POLLIN))
> > + return 0;
>
> Why the polling code, and not just block on splice?
To work around older kernels that don't have the splice(2)
O_NONBLOCKING fix[1] for pipes.
An alternative would be to configure SIGINT not to auto restart
syscalls (which is the default afaik). Then splice(2) will return
EAGAIN and will can restart it with SPLICE_F_NONBLOCK flag on.
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ee5e001196d1345b8fee25925ff5f1d67936081e
next prev parent reply other threads:[~2019-04-03 13:11 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-02 13:45 [RFC PATCH v9 00/11] Add VM kernel tracing over vsockets and FIFOs Slavomir Kaslev
2019-04-02 13:45 ` [RFC PATCH v9 01/11] trace-cmd: Make ports unsigned int Slavomir Kaslev
2019-04-03 13:00 ` Steven Rostedt
2019-04-03 13:14 ` Slavomir Kaslev
2019-04-02 13:45 ` [RFC PATCH v9 02/11] trace-cmd: Detect if vsockets are available Slavomir Kaslev
2019-04-02 13:45 ` [RFC PATCH v9 03/11] trace-cmd: Add tracecmd_create_recorder_virt function Slavomir Kaslev
2019-04-03 13:02 ` Steven Rostedt
2019-04-03 13:12 ` Slavomir Kaslev
2019-04-02 13:45 ` [RFC PATCH v9 04/11] trace-cmd: Add TRACE_REQ and TRACE_RESP messages Slavomir Kaslev
2019-04-02 13:45 ` [RFC PATCH v9 05/11] trace-cmd: Add buffer instance flags for tracing in guest and agent context Slavomir Kaslev
2019-04-02 13:45 ` [RFC PATCH v9 06/11] trace-cmd: Add VM kernel tracing over vsockets transport Slavomir Kaslev
2019-04-02 13:45 ` [RFC PATCH v9 07/11] trace-cmd: Use splice(2) for vsockets if available Slavomir Kaslev
2019-04-02 13:45 ` [RFC PATCH v9 08/11] trace-cmd: Add `trace-cmd setup-guest` command Slavomir Kaslev
2019-04-02 13:45 ` [RFC PATCH v9 09/11] trace-cmd: Try to autodetect number of guest CPUs in setup-guest if not specified Slavomir Kaslev
2019-04-02 13:45 ` [RFC PATCH v9 10/11] trace-cmd: Add setup-guest flag for attaching FIFOs to the guest VM config Slavomir Kaslev
2019-04-02 13:45 ` [RFC PATCH v9 11/11] trace-cmd: Add splice() recording from FIFO without additional pipe buffer Slavomir Kaslev
2019-04-03 12:55 ` Steven Rostedt
2019-04-03 13:11 ` Slavomir Kaslev [this message]
2019-04-03 13:16 ` Slavomir Kaslev
2019-04-03 13:25 ` Steven Rostedt
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