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SubjectRe: pdflush and dm-crypt
On Mon, Mar 29 2004, Andrew Morton wrote:
> Jens Axboe <axboe@suse.de> wrote:
> >
> > On Mon, Mar 29 2004, Zoltan NAGY wrote:
> > > Hi!
> > >
> > > I've just upgraded the system to 2.6.5-rc2-bk6, and I'm using
> > > dm-crypt. It's a heavily used server, on average 20-30mbit/sec
> > > traffic is on the wire 7/24, and just noticed, that the load is very
> > > high. In every 4-5 sec pdflush takes a lot of cpu... Is this
> > > intentional? I've found a similar question on kerneltrap
> > > (http://kerneltrap.org/node/view/2756), but havent found a solution
> > > yet. I'm just wondering if it is a problem, or it's the normal
> > > behavior? It's a 1.8 P4 with 1G ram and highmem enabled, with 256 bit
> > > aes thru dm-crypt.
> >
> > Try the -mm kernels intead, should have lots better behaviour for
> > pdflush/dm interactions.
> >
>
> How come? Isn't this problem just "gee, we have a lot of stuff to encrypt
> during writeback"? If so, then it should be sufficient to poke a hole in
> the encryption loop?

If that is the problem, then yeah that'd work. I was assuming the 'load'
was just io load and pdflush got stuck on them.

> --- 25/drivers/md/dm-crypt.c~a Mon Mar 29 16:11:49 2004
> +++ 25-akpm/drivers/md/dm-crypt.c Mon Mar 29 16:11:56 2004
> @@ -669,6 +669,7 @@ static int crypt_map(struct dm_target *t
> /* out of memory -> run queues */
> if (remaining)
> blk_congestion_wait(bio_data_dir(clone), HZ/100);
> + cond_resched();
> }

Reminds me, we have to kill that blk_congestion_wait() stuff too.

--
Jens Axboe

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