Date: Tue, 19 Mar 2013 16:57:37 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: Freddie Cash <fjwcash@gmail.com> Cc: FreeBSD Filesystems <freebsd-fs@FreeBSD.org> Subject: Re: Strange slowdown when cache devices enabled in ZFS Message-ID: <51487CE1.5090703@FreeBSD.org> In-Reply-To: <CAOjFWZ5e2t0Y_KOxm%2BGhX%2BzXNPfOXb8HKF4uU%2BQ%2BN5eWQqLtdg@mail.gmail.com> References: <CAOjFWZ6Q=Vs3P-kfGysLzSbw4CnfrJkMEka4AqfSrQJFZDP_qw@mail.gmail.com> <51430744.6020004@FreeBSD.org> <CAOjFWZ5e2t0Y_KOxm%2BGhX%2BzXNPfOXb8HKF4uU%2BQ%2BN5eWQqLtdg@mail.gmail.com>
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on 15/03/2013 16:58 Freddie Cash said the following:
> How does one do that? I've never done that before.
>
> Point me to some docs, and I'll see what I can find out.
hwpmc(4), pmcstat(8)
and/or
/usr/share/dtrace/toolkit/hotkernel
and/or (just an example)
dtrace -n 'profile:::profile-4001 { @stacks[pid, tid, execname, stack()] =
count(); } END { trunc(@stacks, 10); printa(@stacks); }'
> On Fri, Mar 15, 2013 at 4:34 AM, Andriy Gapon <avg@freebsd.org
> <mailto:avg@freebsd.org>> wrote:
>
> on 14/03/2013 20:13 Freddie Cash said the following:
> > the l2arc_feed_thread of zfskern will spin until it takes up 100%
> > of a CPU core
>
> If you see a thread taking 100% where it shouldn't, then just profile it and
> actually see what it's doing.
--
Andriy Gapon
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