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Author SHA1 Message Date
Ævar Arnfjörð Bjarmason
6fae3aaf22 spatchcache: add a ccache-alike for "spatch" 
Add a rather trivial "spatchcache", with this running e.g.:

	make cocciclean
	make contrib/coccinelle/free.cocci.patch \
		SPATCH=contrib/coccicheck/spatchcache \
		SPATCH_FLAGS=--very-quiet

Is cut down from ~20s to ~5s on my system. Much of that is either
fixable shell overhead, or the around 40 files we "CANTCACHE" (see the
implementation).

This uses "redis" as a cache by default, but it's configurable. See
the embedded documentation.

This is *not* like ccache in that we won't cache failed spatch
invocations, or those where spatch suggests changes for us. Those
cases are so rare that I didn't think it was worth the bother, by far
the most common case is that it has no suggested changes. We'll also
refuse to cache any "spatch" invocation that has output on stderr,
which means that "--very-quiet" must be added to "SPATCH_FLAGS".

Because we narrow the cache to that we don't need to save away stdout,
stderr & the exit code. We simply cache the cases where we had no
suggested changes.

Another benchmark is to compare this with the previous
SPATCH_BATCH_SIZE=N, as noted in [1]. Before this (on my 8 core system) running:

	make clean; time make contrib/coccinelle/array.cocci.patch SPATCH_BATCH_SIZE=0

Would take 33s, but with the preceding changes running without this
"spatchcache" is slightly slower, or around 35s:

	make clean; time make contrib/coccinelle/array.cocci.patch

Now doing the same with SPATCH=contrib/coccinelle/spatchcache will
take around 6s, but we'll need to compile the *.o files first to take
full advantage of it (which can be fast with "ccache"):

	make clean; make; time make contrib/coccinelle/array.cocci.patch SPATCH=contrib/coccinelle/spatchcache

1. https://lore.kernel.org/git/YwdRqP1CyUAzCEn2@coredump.intra.peff.net/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
 2022-11-02 21:22:16 -04:00
Ævar Arnfjörð Bjarmason
d0e624aed7 cocci: run against a generated ALL.cocci 
The preceding commits to make the "coccicheck" target incremental made
it slower in some cases. As an optimization let's not have the
many=many mapping of <*.cocci>=<*.[ch]>, but instead concat the
<*.cocci> into an ALL.cocci, and then run one-to-many
ALL.cocci=<*.[ch]>.

A "make coccicheck" is now around 2x as fast as it was on "master",
and around 1.5x as fast as the preceding change to make the run
incremental:

	$ git hyperfine -L rev origin/master,HEAD~,HEAD -p 'make clean' 'make coccicheck SPATCH=spatch COCCI_SOURCES="$(echo $(ls o*.c builtin/h*.c))"' -r 3
	Benchmark 1: make coccicheck SPATCH=spatch COCCI_SOURCES="$(echo $(ls o*.c builtin/h*.c))"' in 'origin/master
	  Time (mean ± σ):      4.258 s ±  0.015 s    [User: 27.432 s, System: 1.532 s]
	  Range (min … max):    4.241 s …  4.268 s    3 runs

	Benchmark 2: make coccicheck SPATCH=spatch COCCI_SOURCES="$(echo $(ls o*.c builtin/h*.c))"' in 'HEAD~
	  Time (mean ± σ):      5.365 s ±  0.079 s    [User: 36.899 s, System: 1.810 s]
	  Range (min … max):    5.281 s …  5.436 s    3 runs

	Benchmark 3: make coccicheck SPATCH=spatch COCCI_SOURCES="$(echo $(ls o*.c builtin/h*.c))"' in 'HEAD
	  Time (mean ± σ):      2.725 s ±  0.063 s    [User: 14.796 s, System: 0.233 s]
	  Range (min … max):    2.667 s …  2.792 s    3 runs

	Summary
	  'make coccicheck SPATCH=spatch COCCI_SOURCES="$(echo $(ls o*.c builtin/h*.c))"' in 'HEAD' ran
	    1.56 ± 0.04 times faster than 'make coccicheck SPATCH=spatch COCCI_SOURCES="$(echo $(ls o*.c builtin/h*.c))"' in 'origin/master'
	    1.97 ± 0.05 times faster than 'make coccicheck SPATCH=spatch COCCI_SOURCES="$(echo $(ls o*.c builtin/h*.c))"' in 'HEAD~'

This can be turned off with SPATCH_CONCAT_COCCI, but as the
beneficiaries of "SPATCH_CONCAT_COCCI=" would mainly be those
developing the *.cocci rules themselves, let's leave this optimization
on by default.

For more information see my "Optimizing *.cocci rules by concat'ing
them" (<220901.8635dbjfko.gmgdl@evledraar.gmail.com>) on the
cocci@inria.fr mailing list.

This potentially changes the results of our *.cocci rules, but as
noted in that discussion it should be safe for our use. We don't name
rules, or if we do their names don't conflict across our *.cocci
files.

To the extent that we'd have any inter-dependencies between rules this
doesn't make that worse, as we'd have them now if we ran "make
coccicheck", applied the results, and would then have (due to
hypothetical interdependencies) suggested changes on the subsequent
"make coccicheck".

Our "coccicheck-test" target makes use of the ALL.cocci when running
tests, e.g. when testing unused.{c,out} we test it against ALL.cocci,
not unused.cocci. We thus assert (to the extent that we have test
coverage) that this concatenation doesn't change the expected results
of running these rules.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
 2022-11-02 21:22:16 -04:00
Ævar Arnfjörð Bjarmason
316e3886e3 cocci: optimistically use COMPUTE_HEADER_DEPENDENCIES 
Improve the incremental rebuilding support of "coccicheck" by
piggy-backing on the computed dependency information of the
corresponding *.o file, rather than rebuilding all <RULE>/<FILE> pairs
if either their corresponding file changes, or if any header changes.

This in effect uses the same method that the "sparse" target was made
to use in c234e8a0ec (Makefile: make the "sparse" target non-.PHONY,
2021-09-23), except that the dependency on the *.o file isn't a hard
one, we check with $(wildcard) if the *.o file exists, and if so we'll
depend on it.

This means that the common case of:

	make
	make coccicheck

Will benefit from incremental rebuilding, now changing e.g. a header
will only re-run "spatch" on those those *.c files that make use of
it:

By depending on the *.o we piggy-back on
COMPUTE_HEADER_DEPENDENCIES. See c234e8a0ec (Makefile: make the
"sparse" target non-.PHONY, 2021-09-23) for prior art of doing that
for the *.sp files. E.g.:

    make contrib/coccinelle/free.cocci.patch
    make -W column.h contrib/coccinelle/free.cocci.patch

Will take around 15 seconds for the second command on my 8 core box if
I didn't run "make" beforehand to create the *.o files. But around 2
seconds if I did and we have those "*.o" files.

Notes about the approach of piggy-backing on *.o for dependencies:

 * It *is* a trade-off since we'll pay the extra cost of running the C
   compiler, but we're probably doing that anyway. The compiler is much
   faster than "spatch", so even though we need to re-compile the *.o to
   create the dependency info for the *.c for "spatch" it's
   faster (especially if using "ccache").

 * There *are* use-cases where some would like to have *.o files
   around, but to have the "make coccicheck" ignore them. See:
   https://lore.kernel.org/git/20220826104312.GJ1735@szeder.dev/

   For those users a:

	make
	make coccicheck SPATCH_USE_O_DEPENDENCIES=

   Will avoid considering the *.o files.

 * If that *.o file doesn't exist we'll depend on an intermediate file
   of ours which in turn depends on $(FOUND_H_SOURCES).

   This covers both an initial build, or where "coccicheck" is run
   without running "all" beforehand, and because we run "coccicheck"
   on e.g. files in compat/* that we don't know how to build unless
   the requisite flag was provided to the Makefile.

   Most of the runtime of "incremental" runs is now spent on various
   compat/* files, i.e. we conditionally add files to COMPAT_OBJS, and
   therefore conflate whether we *can* compile an object and generate
   dependency information for it with whether we'd like to link it
   into our binary.

   Before this change the distinction didn't matter, but now one way
   to make this even faster on incremental builds would be to peel
   those concerns apart so that we can see that e.g. compat/mmap.c
   doesn't depend on column.h.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
 2022-11-02 21:22:16 -04:00
SZEDER Gábor
dd5d052c39 coccicheck: introduce 'pending' semantic patches 
Teach `make coccicheck` to avoid patches named "*.pending.cocci" and
handle them separately in a new `make coccicheck-pending` instead.
This means that we can separate "critical" patches from "FYI" patches.
The former target can continue causing Travis to fail its static
analysis job, while the latter can let us keep an eye on ongoing
(pending) transitions without them causing too much fallout.

Document the intended use-cases around these two targets.
As the process around the pending patches is not yet fully explored,
leave that out.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Based-on-work-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
 2018-11-14 11:22:36 +09:00
brian m. carlson
db1d80b8fa contrib/coccinelle: add basic Coccinelle transforms 
Coccinelle (http://coccinelle.lip6.fr/) is a program which performs
mechanical transformations on C programs using semantic patches.  These
semantic patches can be used to implement automatic refactoring and
maintenance tasks.

Add a set of basic semantic patches to convert common patterns related
to the struct object_id transformation, as well as a README.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
 2016-06-28 11:39:02 -07:00