Messages in this thread | | | From | "roland" <> | Subject | Re: I/O statistics per process | Date | Thu, 28 Sep 2006 22:05:26 +0200 |
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andrew, jay - thank you very much for giving your comments on this issue and discussing this!
> I'd be interested in your opinions on all the above, please.
just kidding here a little bit (pardon!) - but from a user/admin perspective we "just" want something like this:
http://www.my-vserver.de/stuff/linux/process-explorer.png (especially mind the I/O columns in the middle of the screenshot)
awesome tool - but unfortunately mr. russinovich is working for the wrong company/developing for the wrong operating system.... ;)
regards roland
----- Original Message ----- From: "Andrew Morton" <akpm@osdl.org> To: "Jay Lan" <jlan@engr.sgi.com> Cc: "roland" <devzero@web.de>; "Fengguang Wu" <fengguang.wu@gmail.com>; <linux-kernel@vger.kernel.org>; <lserinol@gmail.com> Sent: Thursday, September 28, 2006 9:09 PM Subject: Re: I/O statistics per process
> On Thu, 28 Sep 2006 11:55:38 -0700 > Jay Lan <jlan@engr.sgi.com> wrote: > >> Andrew Morton wrote: >> > On Wed, 27 Sep 2006 23:22:02 +0200 >> > "roland" <devzero@web.de> wrote: >> > >> >>thanks. tried to contact redflag, but they don`t answer. maybe support >> >>is >> >>being on holiday.... !? >> >> >> >>linux kernel hackers - there is really no standard way to watch i/o >> >>metrics >> >>(bytes read/written) at process level? >> > >> > The patch csa-accounting-taskstats-update.patch in current -mm kernels >> > (whcih is planned for 2.6.19) does have per-process chars-read and >> > chars-written accounting ("Extended accounting fields"). That's >> > probably >> > not waht you really want, although it might tell you what you want to >> > know. >> > >> >>it`s extremly hard for the admin to track down, what process is hogging >> >>the >> >>disk - especially if there is more than one task consuming cpu. >> >> Rolend, >> >> The per-process chars-read and chars-writeen accounting is made >> available through taskstats interface (see Documentation/accounting/ >> taskstats.txt) in 2.6.18-mm1 kernel. Unfortunately, the user-space CSA >> package is still a few months away. You may, for now, write your >> own taskstats application or go a long way to port the in-kernel >> implementation of pagg/job/csa. >> >> However, the "Externded acocunting fields" patch does not provide you >> straight forward answer. The patch provides accounting data only at >> process termination (just like the BSD accounting) and it seems that >> you want to see which run-away application (ie, alive) eating up your >> disk. The taskstats interface offers a query mode (command-response), >> but currently only delayacct uses that mode. We would need to make >> those data available in the query mode in order for application to >> see accounting data of live processes. > > ow. That is a rather important enhancement to have. > >> > >> > csa-accounting-taskstats-update.patch makes that information available >> > to >> > userspace. >> > >> > But it's approximate, because >> > >> > - it doesn't account for disk readahead >> > >> > - it doesn't account for pagefault-initiated reads (althought it easily >> > could - Jay?) >> > >> > - it overaccounts for a process writing to an already-dirty page. >> > >> > (We could fix this too: nuke the existing stuff and do >> > >> > current->wchar += PAGE_CACHE_SIZE; >> > >> > in __set_page_dirty_[no]buffers().) (But that ends up being wrong if >> > someone truncates the file before it got written) >> > >> > - it doesn't account for file readahead (although it easily could) >> > >> > - it doesn't account for pagefault-initiated readahead (it could) >> > >> > >> > hm. There's actually quite a lot we could do here to make these fields >> > more accurate and useful. A lot of this depends on what the definition >> > of >> > these fields _is_. Is is just for disk IO? Is it supposed to include >> > console IO, or what? > > I'd be interested in your opinions on all the above, please. >
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