On Friday 23 Mar 2012 16:00:15 Marco Schulze wrote:
> Yes, and yes.
>
> On 23-03-2012 12:43, Matthew Toseland wrote:
> > On Friday 23 Mar 2012 15:29:44 you wrote:
> >> Right now, the map is only used to list class thresholds which are
> >> different from the global threshold, which means it is empty 99% of the
> >> time. This is the simplest solution, but it also means that the
> >> possibility of lock contention is way higher. However, unless this
> >> proves to be very bad in a real run, I'll stick with it.
> > Sounds like you need to use a volatile.
> >
> > Also your design implies that the log level details will be changed to not
> > support wildcards/prefixes?
Is there any way to avoid this? Prefixes are really handy in some debugging
situations. Possibly we could hook into the classloader and apply the wildcards
on loading?
> >> On 23-03-2012 10:39, Matthew Toseland wrote:
> >>> On Friday 23 Mar 2012 00:18:02 Marco Schulze wrote:
> >>>> I already have all but log rotation and async ready, and haven't yet
> >>>> found a single benchmark supporting the use of a branch as the
> >>>> performance holy grail. For example (outputting to /dev/null):
> >>>>
> >>>> public static void main (String[] args) {
> >>>> for (int i = 0; i< 1000000; i++) {
> >>>> Log.fatal (Log.class, Log.class, "akd\n\n", i, '\n',
> >>>> out, ' ');
> >>>> Log.trace (Log.class, Log.class, "akd\n\n", i, '\n',
> >>>> out, ' ');
> >>>> }
> >>>> }
> >>>>
> >>>> Every call means, minimally, varargs boxing, another call (since fatal()
> >>>> and trace() are simple convenience methods) and an isLoggable() check
> >>>> composed by a ConcurrentHashMap lookup against the class name and
> >>>> (possibly) a synchronized read on the global threshold. trace() is
> >>>> filtered but fatal() is not.
> >>> Don't do a synchronized read on the global threshold. Don't do
> >>> synchronized anything. Just recompute all the classes when the thresholds
> >>> change.
> >>>
> >>> However, you still haven't told me how you're going to ensure all classes
> >>> are paged in when you do set all the thresholds in the map?
> >>>> This snipped ran in an average 6.482 seconds. If the call to trace() is
> >>>> commented out (thus removing the filtering overhead), the average falls
> >>>> to 6.366 seconds. Disabling JIT, the figures became 1:37.952 and
> >>>> 1:35.880, respectively. Over a million calls, checking costs only a few
> >>>> milliseconds.
> >>>>
> >>>> To be sure, this is a fairly simple example: it all runs on a single
> >>>> thread, the hash table is empty and the pressure on the GC is low.
> >>>> Still, differences are very small. Plus, there's no overhead due to a
> >>>> dedicated logging thread.
> >>>>
> >>>> On 22-03-2012 18:59, Zlatin Balevsky wrote:
> >>>>> Double-digit millisecond pauses are not nothing. They may be
> >>>>> acceptable right now but unless you can offer a drastically cleaner
> >>>>> syntax Fred should stick with predicates as they are handled much
> >>>>> better by the hotspot jit.
> >>>>>
> >>>>> On Mar 22, 2012 5:36 PM, "Ximin Luo"<infinity0 at gmx.com
> >>>>> <mailto:infinity0 at gmx.com>> wrote:
> >>>>>
> >>>>> Lazy evaluation is trivial.
> >>>>>
> >>>>> Log.info("{1} did {2}",
> >>>>> new Object(){ public String toString() { return ITEM_1; } },
> >>>>> new Object(){ public String toString() { return ITEM_2; } }
> >>>>> );
> >>>>>
> >>>>> Garbage collection with short-lived objects costs next to nothing.
> >>>>>
> >>>>> On 22/03/12 21:15, Zlatin Balevsky wrote:
> >>>>> > Constructing the logging strings is half of the problem. The
> >>>>> amount of garbage
> >>>>> > they will generate will result in significantly more time in
> >>>>> garbage collection
> >>>>> > pauses.
> >>>>> >
> >>>>> > Unless you figure out a way to mimic lazy evaluation you have
> >>>>> to
> >>>>> live with the
> >>>>> > isLoggable predicates. varargs are not an option either
> >>>>> because
> >>>>> they also
> >>>>> > create garbage.
> >>>>> >
> >>>>> > On Mar 22, 2012 8:11 AM, "Marco Schulze"
> >>>>> <marco.c.schulze at gmail.com<mailto:marco.c.schulze at gmail.com>
> >>>>> > <mailto:marco.c.schulze at gmail.com
> >>>>> <mailto:marco.c.schulze at gmail.com>>> wrote:
> >>>>> >
> >>>>> >
> >>>>> >
> >>>>> > On 22-03-2012 08:50, Matthew Toseland wrote:
> >>>>> >
> >>>>> > On Wednesday 21 Mar 2012 21:18:37 Marco Schulze wrote:
> >>>>> >
> >>>>> > There are basically two big concerns regarding
> >>>>> logging in fred:
> >>>>> >
> >>>>> > - Readability and code clutter, which was my
> >>>>> original questioning;
> >>>>> > - Raw throughput, as raised by toad.
> >>>>> >
> >>>>> > Point 1 could mostly be solved by removing any
> >>>>> traces of logMINOR and
> >>>>> > logDEBUG on all but the few places where
> >>>>> generating
> >>>>> messages to be
> >>>>> > logged brings noticeable slowdown. That'd be
> >>>>> enough,
> >>>>> but, personally,
> >>>>> > the mess that the logging backend is does warrant
> >>>>> a
> >>>>> replacement.
> >>>>> > According to toad, the current system needs
> >>>>> log{MINOR,DEBUG} to
> >>>>> > function
> >>>>> > in a timely manner. Based on this, I think we all
> >>>>> agree a
> >>>>> > replacement is
> >>>>> > desirable.
> >>>>> >
> >>>>> > Logging has a few additional requirements:
> >>>>> >
> >>>>> > - Log rotation (possibly live);
> >>>>> > - Reentrant;
> >>>>> > - Per-class filtering;
> >>>>> > - Specific information in log (class-name, for
> >>>>> example).
> >>>>> >
> >>>>> > Now, _any_ library which fits would make me happy,
> >>>>> as long as they
> >>>>> > agree
> >>>>> > to two points:
> >>>>> >
> >>>>> > - Either lightweight or with optional features.
> >>>>> Else, it would only
> >>>>> > transfer bloat to freenet-ext.jar. For example:
> >>>>> log2socket, config
> >>>>> > management and multiple logging instances;
> >>>>> > - Implementable in a few LoC. Specially, it
> >>>>> shouldn't need specialized
> >>>>> > Formatter and Writer.
> >>>>> >
> >>>>> > Plus, it should be fast.
> >>>>> >
> >>>>> > From the quick research I made (yep, too many
> >>>>> lists):
> >>>>> >
> >>>>> > - SLF4J already fails on point one: it is simply a
> >>>>> wrapper;
> >>>>> > - The Java logging API fails on point two:
> >>>>> specialized classes would
> >>>>> > have to be written to deal with log rotation,
> >>>>> per-class filtering and
> >>>>> > formatting, plus a wrapper for
> >>>>> Logger.{info,warning,...}() methods.
> >>>>> > Exactly the same as a custom logger, with one more
> >>>>> dependency and using
> >>>>> > more LoC;
> >>>>> >
> >>>>> > No dependancies, it's part of the JDK, isn't it?
> >>>>> >
> >>>>> > More classes need to be loaded at startup. It's just me
> >>>>> thinking too much.
> >>>>> >
> >>>>> >
> >>>>> > However, if it's not a clearer/simpler API, it
> >>>>> probably
> >>>>> doesn't make
> >>>>> > much sense.
> >>>>> >
> >>>>> > - Log4J seems to fail on point one - it only
> >>>>> lacks a
> >>>>> button that brings
> >>>>> > back the dead. It seems interesting, and I haven't
> >>>>> dropped this yet.
> >>>>> >
> >>>>> > In either case (custom or external), log* would be
> >>>>> banished. Forever.
> >>>>> >
> >>>>> > I don't follow. You object to using a separate logs
> >>>>> folder?
> >>>>> >
> >>>>> > log* == log{MINOR,DEBUG}, not the logs folder.
> >>
>
>
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