From: Robert Richter <rric@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Jean Pihet <jean.pihet@linaro.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Arnaldo Carvalho de Melo <acme@infradead.org>,
Jiri Olsa <jolsa@redhat.com>,
linux-kernel@vger.kernel.org,
Tomasz Nowicki <tomasz.nowicki@linaro.org>
Subject: Re: [PATCH v4 00/16] perf, persistent: Add persistent events
Date: Fri, 9 May 2014 10:52:52 +0200 [thread overview]
Message-ID: <20140509085252.GS32718@rric.localhost> (raw)
In-Reply-To: <20140508183629.GJ12548@pd.tnic>
On 08.05.14 20:36:29, Borislav Petkov wrote:
> On Wed, May 07, 2014 at 07:01:55PM +0200, Robert Richter wrote:
> > For general-purpose... Why 512k buffers are ok? Depending on the
> > event, smaller buffers are maybe good enough, esp. since they are
> > permanently enabled and use system resources. Or, at some point, 512k
> > is not sufficient anymore. You don't want 512k be carved in stone.
>
> Well, if it turns out that 512K is not enough, it will be changed in
> perf itself, right?
This requires patching the kernel.
>
> And we still don't care because no matter the size, the persistent
> buffers overwrite themselves on fill up. If they'd stopped, they're not
> really persistent, right?
If the buffer size does not fit it might either use too much resources
in the system or overwrite its own samples before reading it.
Fixed buffers might work and are good enough in the beginning. If all
users can live with it, fine. But if not, the design does not allow
changes in API without breaking it. What's that I care about and
what's we should think about while designing the i/f.
-Robert
next prev parent reply other threads:[~2014-05-09 8:53 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-07 15:04 [PATCH v4 00/16] perf, persistent: Add persistent events Jean Pihet
2014-04-07 15:04 ` [PATCH 01/16] perf, mmap: Factor out ring_buffer_detach_all() Jean Pihet
2014-04-07 15:04 ` [PATCH 02/16] perf, mmap: Factor out try_get_event()/put_event() Jean Pihet
2014-04-07 15:04 ` [PATCH 03/16] perf, mmap: Factor out perf_alloc/free_rb() Jean Pihet
2014-04-22 14:25 ` Peter Zijlstra
2014-04-07 15:04 ` [PATCH 04/16] perf, mmap: Factor out perf_get_fd() Jean Pihet
2014-04-22 14:27 ` Peter Zijlstra
2014-04-25 13:54 ` Robert Richter
2014-04-25 14:43 ` Peter Zijlstra
2014-04-25 14:52 ` Peter Zijlstra
2014-04-29 15:34 ` Robert Richter
2014-04-07 15:04 ` [PATCH 05/16] perf: Add persistent events Jean Pihet
2014-04-07 15:04 ` [PATCH 06/16] mce, x86: Enable " Jean Pihet
2014-04-07 15:04 ` [PATCH 07/16] perf, persistent: Implementing a persistent pmu Jean Pihet
2014-04-07 15:04 ` [PATCH 08/16] perf, persistent: Exposing persistent events using sysfs Jean Pihet
2014-04-07 15:04 ` [PATCH 09/16] perf, persistent: Use unique event ids Jean Pihet
2014-04-07 15:04 ` [PATCH 10/16] perf, persistent: Implement reference counter for events Jean Pihet
2014-04-07 15:04 ` [PATCH 11/16] perf, persistent: Dynamically resize list of sysfs entries Jean Pihet
2014-04-07 15:04 ` [PATCH 12/16] perf, persistent: ioctl functions to control persistency Jean Pihet
2014-04-07 15:04 ` [PATCH 13/16] perf tools: Rename flex conditions to avoid name conflicts Jean Pihet
2014-04-07 15:04 ` [PATCH 14/16] perf tools: Modify event parser to update event attribute by index Jean Pihet
2014-04-07 15:04 ` [PATCH 15/16] perf tools: Add attr<num> syntax to event parser Jean Pihet
2014-04-07 15:04 ` [PATCH 16/16] perf tools: Retry mapping buffers readonly on EACCES Jean Pihet
2014-04-17 12:44 ` [PATCH v4 00/16] perf, persistent: Add persistent events Jean Pihet
2014-04-17 12:50 ` Borislav Petkov
2014-04-17 13:17 ` Jean Pihet
2014-04-17 13:21 ` Borislav Petkov
2014-04-22 8:20 ` Jean Pihet
2014-04-22 10:07 ` Jean Pihet
2014-04-22 10:20 ` Borislav Petkov
2014-05-06 12:39 ` Robert Richter
2014-05-06 18:50 ` Borislav Petkov
2014-05-06 18:53 ` Borislav Petkov
2014-05-07 16:44 ` Robert Richter
2014-05-08 18:23 ` Borislav Petkov
2014-05-09 9:17 ` Robert Richter
2014-05-06 18:58 ` Borislav Petkov
2014-05-07 17:01 ` Robert Richter
2014-05-08 18:36 ` Borislav Petkov
2014-05-09 8:52 ` Robert Richter [this message]
2014-05-09 10:17 ` Borislav Petkov
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