[PATCH] D16726: [Profiling] Speed up unittests by ~5x

Mon Feb 8 16:38:17 PST 2016

On Mon, Feb 8, 2016 at 4:25 PM, Xinliang David Li <davidxl at google.com>
wrote:

> On Mon, Feb 8, 2016 at 4:12 PM, David Blaikie <dblaikie at gmail.com> wrote:
> >
> >
> > On Mon, Feb 8, 2016 at 4:00 PM, Xinliang David Li <davidxl at google.com>
> > wrote:
> >>
> >> Yes, if we talk about all tests in different repos collectively, 0 is
> >> probably covered -- but that is still an assumption from the
> >> unittest's point of view.
> >
> >
> > Ah, sure - I agree it (along with any other API surface area) should be
> > covered by a unit test, even if the codepath is also covered by a higher
> > level test of some kind.
> >
> > But it looks like the 0 padding case is covered by other /unit/ tests in
> the
> > same file.
>
> AFAIK, this is the only unittest that covers 0 padding case.
>

Presumably any other test testing InstrProfSymtab::create tests the zero
padding case, so far as I'm understanding?
(instr_prof_symtab_test, instr_prof_symtab_module_test?)

(also, as I look at this - the tests seem generally pretty repetitive and
brittle - repeating the same string in many places, for example & seem
overly verbose, testing several more inputs than seem
necessary/constructive (instr_prof_symtab_test tests 5 strings - why not
one or two? instr_prof_symtab_module_test tests even more... - no tests
seem to test a failed lookup (getFuncName with a hash that is not present))

It looks like this could be simplified across the board & make it clearer
what's being tested and how it's covering all the functionality of the
InstrProfRecord class.

>
> > This seems like a reasonable case of test case reduction by
> > combination (if you have {a, b} x {x, y} to test you can test it in two
> > cases {a, x}, {b, y} rather than running 4 tests, since the features are
> > independent).
>
> We need to be very careful about reducing {a,b}x{x,y} into {a,x} and
> {b,y} though -- it makes explicit assumption about the implementation
> -- there might be subtle dependencies there..
>

Agreed, though it is impractical to assume everything's related to
everything else - testing would be prohibitive. So we generally test fairly
precisely/narrowly within the regression suite, and leave it to integration
tests (like the test-suite, self hosts, etc) to test more broadly for the
cross-functional interactions.

That's not to say that some tests don't end up a bit redundant so as to get
more explicit coverage.

- David

>
> David
>
> >
> >>
> >>
> >> David
> >>
> >> On Mon, Feb 8, 2016 at 3:55 PM, David Blaikie <dblaikie at gmail.com>
> wrote:
> >> >
> >> >
> >> > On Mon, Feb 8, 2016 at 3:53 PM, Xinliang David Li <davidxl at google.com
> >
> >> > wrote:
> >> >>
> >> >> On Mon, Feb 8, 2016 at 3:30 PM, David Blaikie <dblaikie at gmail.com>
> >> >> wrote:
> >> >> >
> >> >> >
> >> >> > On Mon, Feb 8, 2016 at 3:17 PM, Xinliang David Li
> >> >> > <davidxl at google.com>
> >> >> > wrote:
> >> >> >>
> >> >> >> On Mon, Feb 8, 2016 at 3:12 PM, David Blaikie <dblaikie at gmail.com
> >
> >> >> >> wrote:
> >> >> >> >
> >> >> >> >
> >> >> >> > On Mon, Feb 8, 2016 at 3:08 PM, Xinliang David Li
> >> >> >> > <davidxl at google.com>
> >> >> >> > wrote:
> >> >> >> >>
> >> >> >> >> On Mon, Feb 1, 2016 at 10:44 AM, David Blaikie
> >> >> >> >> <dblaikie at gmail.com>
> >> >> >> >> wrote:
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > On Fri, Jan 29, 2016 at 5:58 PM, Xinliang David Li
> >> >> >> >> > <davidxl at google.com>
> >> >> >> >> > wrote:
> >> >> >> >> >>
> >> >> >> >> >> To clarify, it is not 128 iterations, but creating a symbol
> >> >> >> >> >> table
> >> >> >> >> >> with
> >> >> >> >> >> 128 entries -- which is a reasonable size.
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > We don't generally test on "realistic" sized inputs in the
> >> >> >> >> > regression
> >> >> >> >> > suite.
> >> >> >> >> > We write targeted tests for functionality. Broad testing is
> >> >> >> >> > done
> >> >> >> >> > in
> >> >> >> >> > the
> >> >> >> >> > test-suite and other integration level testing.
> >> >> >> >> >
> >> >> >> >> >>
> >> >> >> >> >> Test coverage wise, it is probably the same as a 3-entry
> >> >> >> >> >> symtab.
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > Then let's use a 3-entry symtab.
> >> >> >> >> >
> >> >> >> >> > (why 3? Because it tests the boundaries (first and last) and
> >> >> >> >> > one
> >> >> >> >> > "normal"
> >> >> >> >> > case of a non-boundary value - while the boundaries probably
> >> >> >> >> > aren't
> >> >> >> >> > interesting in this algorithm, it's cheap enough to just
> follow
> >> >> >> >> > that
> >> >> >> >> > common
> >> >> >> >> > practice in test case design)
> >> >> >> >>
> >> >> >> >> Will update it to 3.
> >> >> >> >>
> >> >> >> >> >
> >> >> >> >> > I'm also curious about the padding parameter - what does it
> do?
> >> >> >> >> > Choose
> >> >> >> >> > how
> >> >> >> >> > many null characters go between each value? What effect does
> >> >> >> >> > that
> >> >> >> >> > have/why
> >> >> >> >> > is that a tuning parameter? (understanding what it's for can
> >> >> >> >> > help
> >> >> >> >> > us
> >> >> >> >> > choose
> >> >> >> >> > appropriate test cases/coverage for that functionality)
> >> >> >> >>
> >> >> >> >> Internal padding bytes (for alignment to 4 bytes) can be zero
> to
> >> >> >> >> 3.
> >> >> >> >
> >> >> >> >
> >> >> >> > Any idea what's particularly useful to test here? (does it just
> >> >> >> > assert
> >> >> >> > that
> >> >> >> > the parameter is [0,3] ? Or does it have well defined behavior
> >> >> >> > (returning an
> >> >> >> > error code? doing something else?) outside that range? is any
> case
> >> >> >> > more
> >> >> >> > interesting than any other - or just a simple loop for
> [0,Padding]
> >> >> >> > done
> >> >> >> > at
> >> >> >> > some point in the algorithm? Does anything test that the
> algorithm
> >> >> >> > emitted
> >> >> >> > the right padding?)
> >> >> >>
> >> >> >> It tests that the reader is (flexible) and capable of handing
> >> >> >> padding
> >> >> >> bytes not produced by the writer.  How many paddings should be
> >> >> >> emitted
> >> >> >> is not specified. For instance, if some producer forces 8 byte
> >> >> >> alignment, it should be handled too.
> >> >> >
> >> >> >
> >> >> > Ah, OK - perhaps we could just test one pseudo-random (if it's
> really
> >> >> > just a
> >> >> > "while (null byte)" loop to ignore the padding - I'd probably pick
> 2
> >> >> > bytes
> >> >> > of padding, but don't mind any small number) amount of padding to
> >> >> > test
> >> >> > that
> >> >> > the reader ignores it, rather than testing several amounts of
> >> >> > padding?
> >> >> > Alternatively/in addition, might be good to test these features
> >> >> > separately
> >> >> > to make triage easier? Rather than combining compression and
> padding
> >> >> > together - unless there's an interesting interaction between the
> two
> >> >> > features in the implementation?
> >> >> >
> >> >>
> >> >> I think 0 is more special here, so I would pick 0 and 1 byte.
> >> >
> >> >
> >> > Is zero bytes of padding not already covered by any other tests? (I
> >> > assume
> >> > it's covered by most tests as it sounds like it's the common case?)
> >> >
> >> >>
> >> >> > You say "padding bytes not produced by the writer" - does the
> writer
> >> >> > produce
> >> >> > zero bytes of padding, or some amount of padding that's just not
> the
> >> >> > same
> >> >> > amounts as are being tested here?
> >> >>
> >> >> The writer can produce 0 or more padding bytes, the assembler and
> >> >> linker may or may not pad more. The purpose of the testing is that
> the
> >> >> reader does not depend/care about those behavior.
> >> >>
> >> >> David
> >> >>
> >> >> >
> >> >> > - David
> >> >
> >> >
> >
> >
>
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