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Re: kern/54727: writing a large file causes unreasonable system behaviour
The following reply was made to PR kern/54727; it has been noted by GNATS.
From: "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>
Cc: David Holland <dholland-bugs%netbsd.org@localhost>
Subject: Re: kern/54727: writing a large file causes unreasonable system
Date: Mon, 9 Dec 2019 12:21:19 +0100
> On 6. Dec 2019, at 04:45, David Holland <dholland-bugs%netbsd.org@localhost> wrote:
> The following reply was made to PR kern/54727; it has been noted by GNATS.
> From: David Holland <dholland-bugs%netbsd.org@localhost>
> To: gnats-bugs%netbsd.org@localhost
> Subject: Re: kern/54727: writing a large file causes unreasonable system
> Date: Fri, 6 Dec 2019 03:42:06 +0000
> On Sun, Dec 01, 2019 at 07:00:00AM +0000, spz%NetBSD.org@localhost wrote:
>> running "ssh othersystem dobackup > /storage/file" generating
>> a large file while otherwise idle, causes the system to hang
>> (no response in 5 minutes on serial console, ddb ps shows
>> daemons memory starved or missing) or with
>> "sysctl -w kern.maxvnodes=10000", pgdaemon spinning several minutes
>> before any new program can start.
>> "vmstat 1" shows:
> two notes:
> (1) mlelstv mentioned in chat the other day that all file pages were
> active (rather than inactive) and this seems broken;
This happens for me too. Looks like:
- we are low on memory.
- nearly all pages are active and belong to ONE vnode (the large file
we are currently creating).
- pagedaemon ends up in uvmpdpol_balancequeue() to increase the number
of inactive pages.
- often the one vnode v_interlock is held by another thread
so uvmpd_trylockowner(p) fails for nearly all active pages.
- the pagedaemon starts busy looping until it finds this vnode
unlocked and everything proceeds.
> (2) while chasing something else related today a number of people
> found that all their vnodes were active (rather than inactive),
> probably for the same reason, and this also seems broken.
If this is with "pstat -v" there is a small error in the kernel,
the usecount must be decremented by one.
> also this problem probably should be filed as a release stopper :-(
Not for -9, I had this problem in -8 too.
J. Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig (Germany)
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