[haiku-bugs] Re: [Haiku] #9019: add iotop utility
- From: "anevilyak" <trac@xxxxxxxxxxxx>
- Date: Sun, 23 Sep 2012 20:44:37 -0000
#9019: add iotop utility
-----------------------------------------------+---------------------------
Reporter: Prasad | Owner: nobody
Type: enhancement | Status: new
Priority: normal | Milestone: R1
Component: Applications/Command Line Tools | Version:
Resolution: | R1/Development
Blocked By: | Keywords:
Has a Patch: 1 | Blocking:
| Platform: All
-----------------------------------------------+---------------------------
Comment (by anevilyak):
Replying to [comment:5 Prasad]:
> Accounting for IOs can be performed at various levels, for example:
read, write system calls or, as you pointed out, when a an IO is submitted
to the device.
The syscalls can't really report accurate/meaningful stats though, as
they're completely unaware of a) any ancillary operations that are an
indirect result of their particular request, and b) how many operations a
given request actually resulted in. To illustrate, consider the case of
creating/deleting files. The syscall layer has absolutely no idea as to
how much I/O such an operation actually results in since that completely
depends on what housekeeping metadata operations the underlying filesystem
had to do. Likewise, writing to a file might well result in the filesystem
having to allocate more blocks for it, which also incurs extra operations
outside of the requested write. Furthermore, if the I/O scheduler batches
reads/writes into a single call, the syscall interface wouldn't know that
either. It also wouldn't be aware if the underlying filesystem/device is
in fact a RAID or other form of distributed storage that resulted in
duplicate I/O operations being dispatched to multiple devices. Given all
these caveats, accounting via the syscall interface presents at best an
incomplete picture, and at worst an outright misleading one, which renders
it pretty much useless unless your only goal is to print some numbers.
--
Ticket URL: <http://dev.haiku-os.org/ticket/9019#comment:8>
Haiku <http://dev.haiku-os.org>
Haiku - the operating system.
Other related posts:
