Re: git: 730ea72c706e - main - cam(4): Limit search for disks in SES enclosure by single bus

On Tue, Oct 5, 2021 at 1:55 PM Alexander Motin <mav@freebsd.org> wrote:
>
> On 05.10.2021 15:48, Alan Somers wrote:
> > On Tue, Oct 5, 2021 at 1:41 PM Alexander Motin <mav@freebsd.org> wrote:
> >>
> >> On 05.10.2021 15:14, Alan Somers wrote:
> >>> On Tue, Oct 5, 2021 at 1:04 PM Alexander Motin <mav@freebsd.org> wrote:
> >>>>
> >>>> The branch main has been updated by mav:
> >>>>
> >>>> URL: https://cgit.FreeBSD.org/src/commit/?id=730ea72c706ef8e025616772cfd86fd89ed3d42e
> >>>>
> >>>> commit 730ea72c706ef8e025616772cfd86fd89ed3d42e
> >>>> Author:     Alexander Motin <mav@FreeBSD.org>
> >>>> AuthorDate: 2021-10-05 19:01:16 +0000
> >>>> Commit:     Alexander Motin <mav@FreeBSD.org>
> >>>> CommitDate: 2021-10-05 19:01:16 +0000
> >>>>
> >>>>     cam(4): Limit search for disks in SES enclosure by single bus
> >>>>
> >>>>     At least for SAS that we only support now disks are typically
> >>>>     connected to the same bus as the enclosure.  Limiting the search
> >>>>     scope makes it much faster on systems with multiple buses and
> >>>>     thousands of disks.
> >>>>
> >>>>     Reviewed by:    imp
> >>>>     MFC after:      2 weeks
> >>>>     Sponsored by:   iXsystems, Inc.
> >>>>     Differential Revision:  https://reviews.freebsd.org/D32305
> >>>> ---
> >>>>  sys/cam/scsi/scsi_enc_ses.c | 8 ++++++++
> >>>>  1 file changed, 8 insertions(+)
> >>>>
> >>>> diff --git a/sys/cam/scsi/scsi_enc_ses.c b/sys/cam/scsi/scsi_enc_ses.c
> >>>
> >>>
> >>> Sounds juicy.  Do you have any benchmarks?
> >>
> >> I don't think we've benchmarked that system with payload yet, if that is
> >> what you mean, polishing usability.  But I don't think there can be too
> >> much interesting, since big speeds don't require so many HDDs these
> >> days, but much smaller number of SSDs instead.  This particular system
> >> is about capacity -- ~20PiB raw on 1248 disks in one ZFS pool. :)
> >
> > 1248 disks?  That's huge.  But I'm not asking about throughput.  Your
> > commit message said "much faster".  What operation is "much faster"?
> > Enumerating disks at startup?  That would be useful.
>
> I don't think you notice the difference on startup, too many other
> things going on, but during idle it reduces periodic CPU load spikes by
> enc_daemon processes by several times, proportionally to the number of
> HBAs/buses.  More annoyance than a real problem though.
>
> --
> Alexander Motin

Yeah, I've noticed those occasional enc_daemon spikes.  I was never
sure what it was doing.  Thanks for the fix!  I'm looking forward to
13.1 a little bit more now.