Linux-Trace-Devel Archive on lore.kernel.org
 help / Atom feed
From: Slavomir Kaslev <kaslevs@vmware.com>
To: linux-trace-devel@vger.kernel.org
Cc: rostedt@goodmis.org, ykaradzhov@vmware.com, tstoyanov@vmware.com
Subject: [PATCH v4 8/8] trace-cmd: Use splice(2) for vsock sockets if available
Date: Wed, 16 Jan 2019 15:43:07 +0200
Message-ID: <20190116134307.4185-9-kaslevs@vmware.com> (raw)
In-Reply-To: <20190116134307.4185-1-kaslevs@vmware.com>

Detect if splice(2) reading is supported for vsock sockets (Linux 4.20 and
later) and use it, or fallback to read/write-ing otherwise.

Signed-off-by: Slavomir Kaslev <kaslevs@vmware.com>
---
 tracecmd/trace-record.c | 59 ++++++++++++++++++++++++++++++++++++++---
 1 file changed, 56 insertions(+), 3 deletions(-)

diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
index 1622b5e..cd80462 100644
--- a/tracecmd/trace-record.c
+++ b/tracecmd/trace-record.c
@@ -2658,12 +2658,61 @@ static int open_vsock(unsigned int cid, unsigned int port)
 
 	return sd;
 }
+
+static int try_splice_read_vsock(void)
+{
+	int ret, sd, brass[2];
+
+	sd = socket(AF_VSOCK, SOCK_STREAM, 0);
+	if (sd < 0)
+		return sd;
+
+	ret = pipe(brass);
+	if (ret < 0)
+		goto out_close_sd;
+
+	/*
+	 * On kernels that don't support splice reading from vsock sockets
+	 * this will fail with EINVAL, or ENOTCONN otherwise.
+	 * Technically, it should never succeed but if it does, claim splice
+	 * reading is supported.
+	 */
+	ret = splice(sd, NULL, brass[1], NULL, 10, 0);
+	if (ret < 0)
+		ret = errno != EINVAL;
+	else
+		ret = 1;
+
+	close(brass[0]);
+	close(brass[1]);
+out_close_sd:
+	close(sd);
+	return ret;
+}
+
+static bool can_splice_read_vsock(void)
+{
+	static bool initialized, res;
+
+	if (initialized)
+		return res;
+
+	res = try_splice_read_vsock() > 0;
+	initialized = true;
+	return res;
+}
+
 #else
 static inline int open_vsock(unsigned int cid, unsigned int port)
 {
 	die("vsock is not supported");
 	return -1;
 }
+
+static bool can_splice_read_vsock(void)
+{
+	return false;
+}
 #endif
 
 static int do_accept(int sd)
@@ -2868,13 +2917,16 @@ create_recorder_instance(struct buffer_instance *instance, const char *file, int
 
 	if (instance->flags & BUFFER_FL_GUEST) {
 		int sd;
+		unsigned int flags;
 
 		sd = open_vsock(instance->cid, instance->client_ports[cpu]);
 		if (sd < 0)
 			die("Failed to connect to agent");
 
-		return tracecmd_create_recorder_virt(
-			file, cpu, recorder_flags | TRACECMD_RECORD_NOSPLICE, sd);
+		flags = recorder_flags;
+		if (!can_splice_read_vsock())
+			flags |= TRACECMD_RECORD_NOSPLICE;
+		return tracecmd_create_recorder_virt(file, cpu, flags, sd);
 	}
 
 	if (brass)
@@ -2928,7 +2980,8 @@ static int create_recorder(struct buffer_instance *instance, int cpu,
 
 		if (instance->flags & BUFFER_FL_AGENT) {
 			fd = do_accept(instance->fds[cpu]);
-			flags |= TRACECMD_RECORD_NOSPLICE;
+			if (!can_splice_read_vsock())
+				flags |= TRACECMD_RECORD_NOSPLICE;
 		} else {
 			fd = connect_port(host, instance->client_ports[cpu]);
 		}
-- 
2.19.1


      parent reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-16 13:42 [PATCH v4 0/8] Add VM kernel tracing over vsock sockets Slavomir Kaslev
2019-01-16 13:43 ` [PATCH v4 1/8] trace-cmd: Minor refactoring Slavomir Kaslev
2019-01-16 13:43 ` [PATCH v4 2/8] trace-cmd: Detect if vsock sockets are available Slavomir Kaslev
2019-01-16 13:43 ` [PATCH v4 3/8] trace-cmd: Add tracecmd_create_recorder_virt function Slavomir Kaslev
2019-01-16 13:43 ` [PATCH v4 4/8] trace-cmd: Use unsigned int for trace-cmd client ports Slavomir Kaslev
2019-01-16 13:43 ` [PATCH v4 5/8] trace-cmd: Add TRACE_REQ and TRACE_RESP messages Slavomir Kaslev
2019-01-16 14:19   ` Steven Rostedt
2019-01-16 13:43 ` [PATCH v4 6/8] trace-cmd: Add buffer instance flags for tracing in guest and agent context Slavomir Kaslev
2019-01-16 13:43 ` [PATCH v4 7/8] trace-cmd: Add VM kernel tracing over vsock sockets transport Slavomir Kaslev
2019-01-16 13:43 ` Slavomir Kaslev [this message]

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190116134307.4185-9-kaslevs@vmware.com \
    --to=kaslevs@vmware.com \
    --cc=linux-trace-devel@vger.kernel.org \
    --cc=rostedt@goodmis.org \
    --cc=tstoyanov@vmware.com \
    --cc=ykaradzhov@vmware.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Trace-Devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-trace-devel/0 linux-trace-devel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-trace-devel linux-trace-devel/ https://lore.kernel.org/linux-trace-devel \
		linux-trace-devel@vger.kernel.org linux-trace-devel@archiver.kernel.org
	public-inbox-index linux-trace-devel


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-trace-devel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox