Re: CVS commit: src/sys/kern

[Maxime Villard <max%m00nbsd.net@localhost>]

Le 30/09/2019 à 20:51, Nick Hudson a écrit :
> > On 30 Sep 2019, at 18:06, Tobias Nygren <tnn%netbsd.org@localhost> wrote:
> >
> > On Mon, 23 Sep 2019 05:39:59 +0000
> > Nick Hudson <skrll%netbsd.org@localhost> wrote:
> >
> > > Modified Files:
> > >     src/sys/kern: subr_pool.c
> > >
> > > Log Message:
> > > Enable POOL_REDZONE with DIAGNOSTIC.
> > >
> > > The bug in the arm pmap was fixed long ago.
> > >
> > >
> > > To generate a diff of this commit:
> > > cvs rdiff -u -r1.258 -r1.259 src/sys/kern/subr_pool.c
> >
> > Hi,
> >
> > I see 30% packet loss on my BananaPi evbarm system with -current.
> > I bisected it to the above change. It may have had unintended
> > side effects.
>
> This is maxv’s change really - feel free to revert
>
> Sounds like it corrupts pool allocated memory in some cases

I have rarely seen a memory corruption that cleanly drops packets.

Rather, it just seems to me that the board has limited ram, the redzone adds a
2-byte overhead, in the specific case of mbufs that means we lose one item per
page, and the limit on the pool is reached as a result.

Perhaps a useful change would be to drop the redzone if the 2-byte poison
turns out to cost (too much) more than two bytes.