From: Mike Snitzer <snitzer@redhat.com>
To: Steven Rostedt <srostedt@redhat.com>
Cc: Morgan Mears <morgan.mears@netapp.com>,
Heinz Mauelshagen <heinzm@redhat.com>, Thornber <ejt@redhat.com>,
device-mapper development <dm-devel@redhat.com>,
Joe@redhat.com, Alasdair G Kergon <agk@redhat.com>
Subject: Re: [PATCH 21/24] dm cache: add trc policy shim
Date: Fri, 1 Nov 2013 19:38:17 -0400 [thread overview]
Message-ID: <20131101233817.GA26314@redhat.com> (raw)
In-Reply-To: <1383341958.9311.19.camel@fedora>
On Fri, Nov 01 2013 at 5:39pm -0400,
Steven Rostedt <srostedt@redhat.com> wrote:
> > >
> > > Think this would take care of it (not full-blown tracepoints like
> > > blktrace but certainly more performant than standard printk):
>
> What's wrong with full blown tracepoints?
Nothing. Just wasn't as quick to switch to while keeping the intent of
the original implementation.
> > I folded this trace_printk change in and renamed from trc to trace, see:
> > https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=f6f5db50495b16ff23a0febf38f9ee9d964b12dd
> >
>
> Please please please DO NOT USE TRACE_PRINTK!
Sure, I'll have a look at using proper tracepoints. Worst case, in the
near-term, we drop this type of patch for v3.13 considering how close we
are to merge.
> It's a debugging tool, and should never be used in the kernel proper. It
> was meant for users to use it for debugging and then strip it out.
>
> Now what you could do is to set up tracepoints to record the information
> you want, either in the function itself, or add the wrapper function too
> as a separate policy. Not sure if that would be any help or not.
>
> But unless this is something that is considered "debug use only" and
> never put into a production kernel, do not use trace_printk().
It really is debug only, but I cannot promise nobody will ever add a
trace layer in production -- especially if it is as easy as using
"trace+mq" vs "mq" when specifying the policy name.
> Note, tracepoints will also give you the ability to pick and choose the
> traces instead of doing it by trace_level.
Yeap, I'm aware.
Thanks for your feedback Steve.
next prev parent reply other threads:[~2013-11-01 23:38 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-24 18:30 [PATCH 00/24] dm cache: proposed changes for v3.13 merge Mike Snitzer
2013-10-24 18:30 ` [PATCH 01/24] dm: nest targets used for testing under DM_TEST_TARGETS Mike Snitzer
2013-10-24 23:17 ` Alasdair G Kergon
2013-10-25 19:25 ` Mike Snitzer
2013-10-25 19:29 ` Alasdair G Kergon
2013-10-24 23:51 ` Alasdair G Kergon
2013-10-24 18:30 ` [PATCH 02/24] dm space map disk: optimise sm_disk_dec_block Mike Snitzer
2013-10-24 18:30 ` [PATCH 03/24] dm cache policy: remove return from void policy_remove_mapping Mike Snitzer
2013-10-24 18:30 ` [PATCH 04/24] dm cache policy mq: a few small fixes Mike Snitzer
2013-10-24 18:30 ` [PATCH 05/24] dm cache policy mq: implement writeback_work() and mq_{set, clear}_dirty() Mike Snitzer
2013-10-25 16:06 ` Alasdair G Kergon
2013-10-25 19:18 ` Mike Snitzer
2013-10-24 18:30 ` [PATCH 06/24] dm cache policy mq: return NULL if mq->free list is empty in alloc_entry Mike Snitzer
2013-10-25 16:37 ` Alasdair G Kergon
2013-10-25 20:44 ` Mike Snitzer
2013-10-25 22:36 ` Heinz Mauelshagen
2013-10-29 14:49 ` [PATCH 06/24 v2] dm cache policy mq: return NULL from alloc_entry if cache is full Mike Snitzer
2013-10-24 18:30 ` [PATCH 07/24] dm cache: be much more aggressive about promoting writes to discarded blocks Mike Snitzer
2013-10-24 18:30 ` [PATCH 08/24] dm cache metadata: return bool from __superblock_all_zeroes Mike Snitzer
2013-10-24 18:30 ` [PATCH 09/24] dm cache metadata: check the metadata version when reading the superblock Mike Snitzer
2013-10-25 17:07 ` Alasdair G Kergon
2013-10-25 19:53 ` Mike Snitzer
2013-10-24 18:30 ` [PATCH 10/24] dm cache policy: variable hints support Mike Snitzer
2013-10-24 18:30 ` [PATCH 11/24] dm table: print error on preresume failure Mike Snitzer
2013-10-25 19:22 ` Alasdair G Kergon
2013-10-25 19:58 ` Mike Snitzer
2013-10-24 18:30 ` [PATCH 12/24] dm cache: add passthrough mode Mike Snitzer
2013-10-24 18:30 ` [PATCH 13/24] dm cache policy: have policy_writeback_work return -ENODATA by default Mike Snitzer
2013-10-24 18:30 ` [PATCH 14/24] dm cache: use is_write_io() in more places Mike Snitzer
2013-10-25 19:53 ` Alasdair G Kergon
2013-10-25 20:11 ` Mike Snitzer
2013-10-24 18:30 ` [PATCH 15/24] dm cache: use cell_defer() boolean argument consistently Mike Snitzer
2013-10-24 18:30 ` [PATCH 16/24] dm cache: log error message if dm_kcopyd_copy() fails Mike Snitzer
2013-11-08 13:33 ` Alasdair G Kergon
2013-10-24 18:30 ` [PATCH 17/24] dm cache: use a boolean when setting cache->quiescing Mike Snitzer
2013-11-06 15:02 ` Alasdair G Kergon
2013-11-06 15:25 ` Mike Snitzer
2013-10-24 18:30 ` [PATCH 18/24] dm cache: optimize commit_if_needed Mike Snitzer
2013-10-24 18:30 ` [PATCH 19/24] dm cache: support for stackable caching policies Mike Snitzer
2013-10-24 18:30 ` [PATCH 20/24] dm cache: add era policy shim Mike Snitzer
2013-10-24 18:30 ` [PATCH 21/24] dm cache: add trc " Mike Snitzer
2013-10-25 20:13 ` Alasdair G Kergon
2013-10-25 21:08 ` Mike Snitzer
2013-10-25 22:44 ` Mike Snitzer
2013-11-01 21:39 ` Steven Rostedt
2013-11-01 23:38 ` Mike Snitzer [this message]
2013-10-24 18:30 ` [PATCH 22/24] dm cache: add hints policy Mike Snitzer
2013-10-24 18:30 ` [PATCH 23/24] dm cache: add cache block invalidation API Mike Snitzer
2013-10-24 18:30 ` [PATCH 24/24] dm cache policy era: add cache block invalidation support Mike Snitzer
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