tools/virtiostat: add filter

Add device driver/name filter for virtiostat.

Suggested by Yonghong, also use bpf_probe_read_kernel_str to copy
string from kernel.

Signed-off-by: zhenwei pi <[email protected]>

man/man8/virtiostat.8

@@ -2,7 +2,7 @@
 .SH NAME
 virtiostat \- Trace VIRTIO devices input/output statistics. Uses Linux eBPF/bcc.
 .SH SYNOPSIS
-.B virtiostat [\-h] [\-T] [\-D] [INTERVAL] [COUNT]
+.B virtiostat [\-h] [\-T] [\-D] [-d DRIVER] [-n DEVNAME] [INTERVAL] [COUNT]
 .SH DESCRIPTION
 This tool traces VIRTIO devices input/output statistics. It works in lower
 layer of VIRTIO base driver, so it could trace all the devices of VIRTIO
@@ -25,6 +25,12 @@ Include a time column on output (HH:MM:SS).
 \-D
 Show debug infomation of bpf text.
 .TP
+\-d DRIVER
+Filter for driver name.
+.TP
+\-n DEVNAME
+Filter for device name.
+.TP
 INTERVAL
 Print output every interval seconds.
 .TP
@@ -35,6 +41,10 @@ Total count of trace in seconds.
 Trace virtio device statistics and print 1 second summaries, 10 times:
 #
 .B virtiostat 1 10
+.TP
+Trace virtio block deivces only:
+#
+.B virtiostat -d virtio_blk
 .SH OVERHEAD
 This traces the kernel virtqueue_add_sgs, virtqueue_add_outbuf,
 virtqueue_add_inbuf, virtqueue_add_inbuf_ctx functions.

tools/virtiostat.py

@@ -4,7 +4,7 @@
 # virtiostat Show virtio devices input/output statistics.
 # For Linux, uses BCC, eBPF.
 #
-# USAGE: virtiostat [-h] [-T] [-D] [INTERVAL] [COUNT]
+# USAGE: virtiostat [-h] [-T] [-D] [-d DRIVER] [-n DEVNAME] [INTERVAL] [COUNT]
 #
 # Copyright (c) 2021 zhenwei pi
 # Licensed under the Apache License, Version 2.0 (the "License")
@@ -18,10 +18,12 @@
 
 # arguments
 examples = """examples:
- ./virtiostat # print 3(default) second summaries
- ./virtiostat 1 10 # print 1 second summaries, 10 times
- ./virtiostat -T # show timestamps
- ./virtiostat -D # show debug bpf text
+ ./virtiostat # print 3(default) second summaries
+ ./virtiostat 1 10 # print 1 second summaries, 10 times
+ ./virtiostat -T # show timestamps
+ ./virtiostat -d virtio_blk # only show virtio block devices
+ ./virtiostat -n virtio0 # only show virtio0 device
+ ./virtiostat -D # show debug bpf text
 """
 parser = argparse.ArgumentParser(
  description="Show virtio devices input/output statistics",
@@ -33,6 +35,10 @@
  help="number of outputs")
 parser.add_argument("-T", "--timestamp", action="store_true",
  help="show timestamp on output")
+parser.add_argument("-d", "--driver",
+ help="filter for driver name")
+parser.add_argument("-n", "--devname",
+ help="filter for device name")
 parser.add_argument("-D", "--debug", action="store_true",
  help="print BPF program before starting (for debugging purposes)")
 parser.add_argument("--ebpf", action="store_true",
@@ -52,6 +58,25 @@
 /* typically virtio blk has max SEG of 128 */
 #define SG_MAX 128
 
+/* local strcmp function, max length 16 to protect instruction loops */
+#define CMPMAX 16
+
+static int local_strcmp(const char *cs, const char *ct)
+{
+ int len = 0;
+ unsigned char c1, c2;
+
+ while (len++ < CMPMAX) {
+ c1 = *cs++;
+ c2 = *ct++;
+ if (c1 != c2)
+ return c1 < c2 ? -1 : 1;
+ if (!c1)
+ break;
+ }
+ return 0;
+}
+
 typedef struct virtio_stat {
  char driver[16];
  char dev[12];
@@ -128,6 +153,9 @@
  u64 key = (u64)vq;
  u64 in_bw = 0;
 
+ DRIVERFILTER
+ DEVNAMEFILTER
+
  /* Workaround: separate two count_len() calls, one here and the
  * other below. Otherwise, compiler may generate some spills which
  * harms verifier pruning. This happens in llvm12, but not llvm4.
@@ -138,9 +166,9 @@
 
  vs = stats.lookup(&key);
  if (!vs) {
- bpf_probe_read_kernel(newvs.driver, sizeof(newvs.driver), vq->vdev->dev.driver->name);
- bpf_probe_read_kernel(newvs.dev, sizeof(newvs.dev), vq->vdev->dev.kobj.name);
- bpf_probe_read_kernel(newvs.vqname, sizeof(newvs.vqname), vq->name);
+ bpf_probe_read_kernel_str(newvs.driver, sizeof(newvs.driver), vq->vdev->dev.driver->name);
+ bpf_probe_read_kernel_str(newvs.dev, sizeof(newvs.dev), vq->vdev->dev.kobj.name);
+ bpf_probe_read_kernel_str(newvs.vqname, sizeof(newvs.vqname), vq->name);
  newvs.out_sgs = out_sgs;
  newvs.in_sgs = in_sgs;
  if (out_sgs)
@@ -194,6 +222,29 @@
 }
 """
 
+# filter for driver name
+if args.driver:
+ bpf_text = bpf_text.replace('DRIVERFILTER',
+ """char filter_driver[] = \"%s\";
+ char driver[16];
+ bpf_probe_read_kernel_str(driver, sizeof(driver), vq->vdev->dev.driver->name);
+ if (local_strcmp(filter_driver, driver))
+ return;""" % (args.driver))
+else:
+ bpf_text = bpf_text.replace('DRIVERFILTER', '')
+
+# filter for dev name
+if args.devname:
+ bpf_text = bpf_text.replace('DEVNAMEFILTER',
+ """char filter_devname[] = \"%s\";
+ char devname[16];
+ bpf_probe_read_kernel_str(devname, sizeof(devname), vq->vdev->dev.kobj.name);
+ if (local_strcmp(filter_devname, devname))
+ return;""" % (args.devname))
+else:
+ bpf_text = bpf_text.replace('DEVNAMEFILTER', '')
+
+
 # debug mode: print bpf text
 if args.debug:
  print(bpf_text)

tools/virtiostat_example.txt

@@ -23,24 +23,41 @@ Tracing virtio devices statistics ... Hit Ctrl-C to end.
  9pnet_virtio virtio6 requests 91520 91141 1737364 125320785
 
 
+Show virtio block devices only:
+#./virtiostat.py -d virtio_blk
+Tracing virtio devices statistics ... Hit Ctrl-C to end.
+--------
+ Driver Device VQ Name In SGs Out SGs In BW Out BW
+ virtio_blk virtio4 req.0 4 6 4 24640
+ virtio_blk virtio5 req.0 678756 339378 1390431666 5430048
+
+
 Full USAGE:
 
 #./virtiostat -h
-usage: virtiostat.py [-h] [-T] [-D] [interval] [count]
+usage: virtiostat.py [-h] [-T] [-d DRIVER] [-n DEVNAME] [-D]
+ [interval] [count]
 
 Show virtio devices input/output statistics
 
 positional arguments:
- interval output interval, in seconds
- count number of outputs
+ interval  output interval, in seconds
+ count  number of outputs
 
 optional arguments:
- -h, --help show this help message and exit
- -T, --timestamp show timestamp on output
- -D, --debug print BPF program before starting (for debugging purposes)
+ -h, --help show this help message and exit
+ -T, --timestamp show timestamp on output
+ -d DRIVER, --driver DRIVER
+ filter for driver name
+ -n DEVNAME, --devname DEVNAME
+ filter for device name
+ -D, --debug print BPF program before starting (for debugging
+ purposes)
 
 examples:
- ./virtiostat # print 3(default) second summaries
- ./virtiostat 1 10 # print 1 second summaries, 10 times
- ./virtiostat -T # show timestamps
- ./virtiostat -D # show debug bpf text
+ ./virtiostat # print 3(default) second summaries
+ ./virtiostat 1 10 # print 1 second summaries, 10 times
+ ./virtiostat -T # show timestamps
+ ./virtiostat -d virtio_blk # only show virtio block devices
+ ./virtiostat -n virtio0 # only show virtio0 device
+ ./virtiostat -D # show debug bpf text