Re: [PATCH] perf script: Add a python script to statistic direct io behavior

[David Ahern <dsahern@gmail.com>]

Hi

On 1/31/13 2:08 AM, chenggang.qin@gmail.com wrote:
> From: chenggang.qin@gmail.com
>
> This patch depends on a prev patch: https://lkml.org/lkml/2013/1/29/47
>
> If the engineers want to analyze the direct io behavior of some applications
> without source code, perf tools with some appropriate tracepoints events in the
> VFS subsystem are excellent choice.
>
> Many database systems use their own page cache subsystems and use the direct IO
> to access the disks. Sometimes, the system engineers need to know the misses rate
> of the database system's page cache. This requirements can be satisfied by recording
> the database's file access behavior through the way of direct IO. So, we use 2
> tracepoint events to record the system wide's direct IO behavior. The 2 tracepoint
> events are:
> 1) vfs:direct_io_read
> 2) vfs:direct_io_write
> they were introduced by the patch: https://lkml.org/lkml/2013/1/29/47
> The script direct-io.py are introduced by this patch can record the 2 tracepoint
> events, analyse the sample data, and give a concise report.

What does this option provide that the I/O accounting with taskstats 
(e.g., iotop) does not provide?

David