Subject: Re: uvn_fp1 hang
To: Paul Ripke <>
From: enami tsugutomo <>
List: current-users
Date: 01/21/2003 12:46:09
Paul Ripke <> writes:

> On Friday, January 17, 2003, at 01:25 AM, enami tsugutomo wrote:
> >>> 0xcb893424  6379        4  4         0xc04023d0 cron (flt_pmfail2)
> >>> 0xcb6997c0  6377     4006  4         0xc04023d0 pax (uvn_fp1)
> >>> 0xcb893244  6349    20204  3         0xc07460d4 raidio0 (raidiow)
> >>> 0xcb7fc998  6348    20204  3         0xc04023d0 raid0 (km_getwait2)
> >>
> >> This looks like an "out of kernel memory" problem.
> >
> > More strictly, a backend requires memory to clean dirty page which
> > needs to be cleand to get free memroy, I guess.
> OK, so we aren't reserving enough memory for "emergency" use? Can the
> kernel gods suggest a fix/workaround? I presume this relates to
> NKMEMPAGES? Should I try increasing this? Or will that just postpone
> the inevitable? So many questions...

IIRC, once chuq told that a driver at least should be able to handle
one request without requiring more memory.  It might be true but it
also might be difficult for some drivers like raid driver.

BTW, currently pagedaemon stops initiating new pageout request if
there is enough number of paging requrest ongoing.  Maybe we could do
something to defer the catastrophe (e.g., clean page can be free'ed
without writing to backing store).