Re: vm-pageout-throttling.patch: hanging in throttle_vm_writeout/blk_congestion_wait

From: Sami Farin
Date: Mon Nov 15 2004 - 17:43:31 EST

On Mon, Nov 15, 2004 at 09:56:29PM +0000, Hugh Dickins wrote:
> On Mon, 15 Nov 2004, Sami Farin wrote:
> >
> > this time I had some swapspace on /dev/loop1 (file-backed, reiserfs,
> > loop-AES-2.2d)... I think (!) it caused this deadlock.
> That's not at all surprising. See the swap_extent work Andrew did
> for 2.5 (in mm/swapfile.c), by which swap to a swapfile now avoids
> the filesystem altogether (except while swapon prepares the map of
> disk blocks). By swapping to a loop device over a file, you're
> sneaking past his work, and putting the filesystem back under swap.

Aha... interesting.

> It is begging for deadlocks: I'm not saying it couldn't be got to
> work, and of course it would be nice to boast that there's no such
> issue; but there are so many better places to invest such effort...

So, this was a known issue and it's hard to fix? I didn't know that.

I know it's a "nicer" idea to use some partition for the swap
instead of a file on reiserfs, but I created too small swap partitions
originally and I can't(/bother?) resize the other partitions.
And sometimes some memhog forces me to add even more swap.

BTW. your MUA does not generate References: header field,
it makes scoring hard... With References I would easily
notice when someone writes a followup to some of the threads I have
participated in. But I could patch my MUA... 8)


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