tools: Add guest trace agent as a user tool
This patch adds a user tool, "trace agent" for sending trace data of a guest to
a Host in low overhead. This agent has the following functions:
- splice a page of ring-buffer to read_pipe without memory copying
- splice the page from write_pipe to virtio-console without memory copying
- write trace data to stdout by using -o option
- controlled by start/stop orders from a Host
Changes in v2:
- Cleanup (change fprintf() to pr_err() and an include guard)
Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Acked-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/tools/virtio/virtio-trace/trace-agent-rw.c b/tools/virtio/virtio-trace/trace-agent-rw.c
new file mode 100644
index 0000000..3aace5e
--- /dev/null
+++ b/tools/virtio/virtio-trace/trace-agent-rw.c
@@ -0,0 +1,192 @@
+/*
+ * Read/write thread of a guest agent for virtio-trace
+ *
+ * Copyright (C) 2012 Hitachi, Ltd.
+ * Created by Yoshihiro Yunomae <yoshihiro.yunomae.ez@hitachi.com>
+ * Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
+ *
+ * Licensed under GPL version 2 only.
+ *
+ */
+
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+#include "trace-agent.h"
+
+#define READ_WAIT_USEC 100000
+
+void *rw_thread_info_new(void)
+{
+ struct rw_thread_info *rw_ti;
+
+ rw_ti = zalloc(sizeof(struct rw_thread_info));
+ if (rw_ti == NULL) {
+ pr_err("rw_thread_info zalloc error\n");
+ exit(EXIT_FAILURE);
+ }
+
+ rw_ti->cpu_num = -1;
+ rw_ti->in_fd = -1;
+ rw_ti->out_fd = -1;
+ rw_ti->read_pipe = -1;
+ rw_ti->write_pipe = -1;
+ rw_ti->pipe_size = PIPE_INIT;
+
+ return rw_ti;
+}
+
+void *rw_thread_init(int cpu, const char *in_path, const char *out_path,
+ bool stdout_flag, unsigned long pipe_size,
+ struct rw_thread_info *rw_ti)
+{
+ int data_pipe[2];
+
+ rw_ti->cpu_num = cpu;
+
+ /* set read(input) fd */
+ rw_ti->in_fd = open(in_path, O_RDONLY);
+ if (rw_ti->in_fd == -1) {
+ pr_err("Could not open in_fd (CPU:%d)\n", cpu);
+ goto error;
+ }
+
+ /* set write(output) fd */
+ if (!stdout_flag) {
+ /* virtio-serial output mode */
+ rw_ti->out_fd = open(out_path, O_WRONLY);
+ if (rw_ti->out_fd == -1) {
+ pr_err("Could not open out_fd (CPU:%d)\n", cpu);
+ goto error;
+ }
+ } else
+ /* stdout mode */
+ rw_ti->out_fd = STDOUT_FILENO;
+
+ if (pipe2(data_pipe, O_NONBLOCK) < 0) {
+ pr_err("Could not create pipe in rw-thread(%d)\n", cpu);
+ goto error;
+ }
+
+ /*
+ * Size of pipe is 64kB in default based on fs/pipe.c.
+ * To read/write trace data speedy, pipe size is changed.
+ */
+ if (fcntl(*data_pipe, F_SETPIPE_SZ, pipe_size) < 0) {
+ pr_err("Could not change pipe size in rw-thread(%d)\n", cpu);
+ goto error;
+ }
+
+ rw_ti->read_pipe = data_pipe[1];
+ rw_ti->write_pipe = data_pipe[0];
+ rw_ti->pipe_size = pipe_size;
+
+ return NULL;
+
+error:
+ exit(EXIT_FAILURE);
+}
+
+/* Bind a thread to a cpu */
+static void bind_cpu(int cpu_num)
+{
+ cpu_set_t mask;
+
+ CPU_ZERO(&mask);
+ CPU_SET(cpu_num, &mask);
+
+ /* bind my thread to cpu_num by assigning zero to the first argument */
+ if (sched_setaffinity(0, sizeof(mask), &mask) == -1)
+ pr_err("Could not set CPU#%d affinity\n", (int)cpu_num);
+}
+
+static void *rw_thread_main(void *thread_info)
+{
+ ssize_t rlen, wlen;
+ ssize_t ret;
+ struct rw_thread_info *ts = (struct rw_thread_info *)thread_info;
+
+ bind_cpu(ts->cpu_num);
+
+ while (1) {
+ /* Wait for a read order of trace data by Host OS */
+ if (!global_run_operation) {
+ pthread_mutex_lock(&mutex_notify);
+ pthread_cond_wait(&cond_wakeup, &mutex_notify);
+ pthread_mutex_unlock(&mutex_notify);
+ }
+
+ if (global_sig_receive)
+ break;
+
+ /*
+ * Each thread read trace_pipe_raw of each cpu bounding the
+ * thread, so contention of multi-threads does not occur.
+ */
+ rlen = splice(ts->in_fd, NULL, ts->read_pipe, NULL,
+ ts->pipe_size, SPLICE_F_MOVE | SPLICE_F_MORE);
+
+ if (rlen < 0) {
+ pr_err("Splice_read in rw-thread(%d)\n", ts->cpu_num);
+ goto error;
+ } else if (rlen == 0) {
+ /*
+ * If trace data do not exist or are unreadable not
+ * for exceeding the page size, splice_read returns
+ * NULL. Then, this waits for being filled the data in a
+ * ring-buffer.
+ */
+ usleep(READ_WAIT_USEC);
+ pr_debug("Read retry(cpu:%d)\n", ts->cpu_num);
+ continue;
+ }
+
+ wlen = 0;
+
+ do {
+ ret = splice(ts->write_pipe, NULL, ts->out_fd, NULL,
+ rlen - wlen,
+ SPLICE_F_MOVE | SPLICE_F_MORE);
+
+ if (ret < 0) {
+ pr_err("Splice_write in rw-thread(%d)\n",
+ ts->cpu_num);
+ goto error;
+ } else if (ret == 0)
+ /*
+ * When host reader is not in time for reading
+ * trace data, guest will be stopped. This is
+ * because char dev in QEMU is not supported
+ * non-blocking mode. Then, writer might be
+ * sleep in that case.
+ * This sleep will be removed by supporting
+ * non-blocking mode.
+ */
+ sleep(1);
+ wlen += ret;
+ } while (wlen < rlen);
+ }
+
+ return NULL;
+
+error:
+ exit(EXIT_FAILURE);
+}
+
+
+pthread_t rw_thread_run(struct rw_thread_info *rw_ti)
+{
+ int ret;
+ pthread_t rw_thread_per_cpu;
+
+ ret = pthread_create(&rw_thread_per_cpu, NULL, rw_thread_main, rw_ti);
+ if (ret != 0) {
+ pr_err("Could not create a rw thread(%d)\n", rw_ti->cpu_num);
+ exit(EXIT_FAILURE);
+ }
+
+ return rw_thread_per_cpu;
+}