bpftrace MCP Server

Demonstrations of xfsdist, the Linux bpftrace/eBPF version. xfsdist traces XFS reads, writes, opens, and fsyncs, and summarizes their latency as a power-of-2 histogram. For example: # xfsdist.bt Attaching 9 probes... Tracing XFS operation latency... Hit Ctrl-C to end. ^C @us[xfs_file_write_iter]: [8, 16) 1 |@@@@@@@@@@@@@@@@@@@@@@@@@@ | [16, 32) 2 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| @us[xfs_file_read_iter]: [1] 724 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [2, 4) 137 |@@@@@@@@@ | [4, 8) 143 |@@@@@@@@@@ | [8, 16) 37 |@@ | [16, 32) 11 | | [32, 64) 22 |@ | [64, 128) 7 | | [128, 256) 0 | | [256, 512) 485 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ | [512, 1K) 149 |@@@@@@@@@@ | [1K, 2K) 98 |@@@@@@@ | [2K, 4K) 85 |@@@@@@ | [4K, 8K) 27 |@ | [8K, 16K) 29 |@@ | [16K, 32K) 25 |@ | [32K, 64K) 1 | | [64K, 128K) 0 | | [128K, 256K) 6 | | @us[xfs_file_open]: [1] 1819 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [2, 4) 272 |@@@@@@@ | [4, 8) 0 | | [8, 16) 9 | | [16, 32) 7 | | This output shows a bi-modal distribution for read latency, with a faster mode of 724 reads that took between 0 and 1 microseconds, and a slower mode of over 485 reads that took between 256 and 512 microseconds. It's likely that the faster mode was a hit from the in-memory file system cache, and the slower mode is a read from a storage device (disk). This "latency" is measured from when the operation was issued from the VFS interface to the file system, to when it completed. This spans everything: block device I/O (disk I/O), file system CPU cycles, file system locks, run queue latency, etc. This is a better measure of the latency suffered by applications reading from the file system than measuring this down at the block device interface. Note that this only traces the common file system operations previously listed: other file system operations (eg, inode operations including getattr()) are not traced. There is another version of this tool in bcc: https://github.com/iovisor/bcc The bcc version provides command line options to customize the output.