Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C518CC433EF for ; Tue, 21 Dec 2021 20:40:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234756AbhLUUkT (ORCPT ); Tue, 21 Dec 2021 15:40:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48134 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234161AbhLUUkR (ORCPT ); Tue, 21 Dec 2021 15:40:17 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5777FC061574; Tue, 21 Dec 2021 12:40:17 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 77B60CE1A6F; Tue, 21 Dec 2021 20:40:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68290C36AE9; Tue, 21 Dec 2021 20:40:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1640119213; bh=9Qaez2pN1nIb5XtZINt6HfE4fjEYNO155VTO2E3/lfY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=chydWcyf9l/uExu56OjkFFQJKfsItAlN85Nqp4Kn4/sCZvgoYN7R/GZkMebqKHJel nglmRV5fMoP/o6hbp6rbo9qupPjLdbSQ3fzUfbZiNpfjbp/+hE4zLCmHkOYIZjxmes wHHQqew8gA5AWEfeb/mxZ2zH3G6UP2f0WsaWoN2rJvCIJKt3iy0zOse2QMxjefOpge 5+F5vtJGrmHaUG119GsD/IVvZx6yd8NB02LBK+w4/Zuxi4w/8Vq57T6Zasep26luje G2NkO0GrwyrvmVHnjGNNO3d3ryYVoZSlvCBpvel8g9+KEgAbAYcIjLDye/iSZMYuzX VJExlXAdg7uzw== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 86AFF40B92; Tue, 21 Dec 2021 17:40:10 -0300 (-03) Date: Tue, 21 Dec 2021 17:40:10 -0300 From: Arnaldo Carvalho de Melo To: Leo Yan Cc: carsten.haitzler@foss.arm.com, linux-kernel@vger.kernel.org, coresight@lists.linaro.org, suzuki.poulose@arm.com, mathieu.poirier@linaro.org, mike.leach@linaro.org, inux-perf-users@vger.kernel.org Subject: Re: [PATCH 04/12] perf test: Add beginning of test infra + test to exercise coresight Message-ID: References: <20211215160403.69264-1-carsten.haitzler@foss.arm.com> <20211215160403.69264-4-carsten.haitzler@foss.arm.com> <20211221150349.GB41974@leoy-ThinkPad-X240s> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211221150349.GB41974@leoy-ThinkPad-X240s> X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Tue, Dec 21, 2021 at 11:03:49PM +0800, Leo Yan escreveu: > Hi Carsten, > > On Wed, Dec 15, 2021 at 04:03:55PM +0000, carsten.haitzler@foss.arm.com wrote: > > From: Carsten Haitzler > > > > This adds the initial test harness to run perf record and examine the > > resuling output when coresight is enabled on arm64 and check the > > resulting quality of the output as part of perf test. > > > > Signed-off-by: Carsten Haitzler > > --- > > MAINTAINERS | 3 + > > tools/perf/Makefile.perf | 14 +- > > .../tests/shell/coresight_asm_pure_loop.sh | 18 +++ > > tools/perf/tests/shell/lib/coresight.sh | 130 ++++++++++++++++++ > > tools/perf/tests/shell/tools/Makefile | 26 ++++ > > .../perf/tests/shell/tools/coresight/Makefile | 27 ++++ > > .../shell/tools/coresight/Makefile.miniconfig | 23 ++++ > > .../tools/coresight/asm_pure_loop/Makefile | 30 ++++ > > .../coresight/asm_pure_loop/asm_pure_loop.S | 28 ++++ > > 9 files changed, 297 insertions(+), 2 deletions(-) > > create mode 100755 tools/perf/tests/shell/coresight_asm_pure_loop.sh > > create mode 100644 tools/perf/tests/shell/lib/coresight.sh > > create mode 100644 tools/perf/tests/shell/tools/Makefile > > create mode 100644 tools/perf/tests/shell/tools/coresight/Makefile > > create mode 100644 tools/perf/tests/shell/tools/coresight/Makefile.miniconfig > > create mode 100644 tools/perf/tests/shell/tools/coresight/asm_pure_loop/Makefile > > create mode 100644 tools/perf/tests/shell/tools/coresight/asm_pure_loop/asm_pure_loop.S > > The folder naming is okay for me, but it is cyclic with the format: > "tools/.../tools/". So I am wandering if below two pathes are better? > > tools/perf/tests/shell/prog/coresight/ > or > tools/perf/tests/shell/coresight/ The later, its descriptive enough, I think, and the shortest variant so far. - Arnaldo > I'd like to leave this question for Arnaldo / Jiri for the folder > layout. > > > diff --git a/MAINTAINERS b/MAINTAINERS > > index 13f9a84a617e..d46e8469c467 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -1894,6 +1894,9 @@ F: tools/perf/arch/arm/util/auxtrace.c > > F: tools/perf/arch/arm/util/cs-etm.c > > F: tools/perf/arch/arm/util/cs-etm.h > > F: tools/perf/arch/arm/util/pmu.c > > +F: tools/perf/tests/shell/coresight_* > > +F: tools/perf/tests/shell/tools/Makefile > > +F: tools/perf/tests/shell/tools/coresight/* > > F: tools/perf/util/cs-etm-decoder/* > > F: tools/perf/util/cs-etm.* > > > > diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf > > index 80522bcfafe0..26467a2c71f4 100644 > > --- a/tools/perf/Makefile.perf > > +++ b/tools/perf/Makefile.perf > > @@ -630,7 +630,15 @@ sync_file_range_tbls := $(srctree)/tools/perf/trace/beauty/sync_file_range.sh > > $(sync_file_range_arrays): $(linux_uapi_dir)/fs.h $(sync_file_range_tbls) > > $(Q)$(SHELL) '$(sync_file_range_tbls)' $(linux_uapi_dir) > $@ > > > > -all: shell_compatibility_test $(ALL_PROGRAMS) $(LANG_BINDINGS) $(OTHER_PROGRAMS) > > +TESTS_TOOLS_DIR := $(srctree)/tools/perf/tests/shell/tools > > + > > +tests-tools-targets: FORCE > > + $(Q)$(MAKE) -C $(TESTS_TOOLS_DIR) > > + > > +tests-tools-targets-clean: > > + $(Q)$(MAKE) -C $(TESTS_TOOLS_DIR) clean > > + > > +all: shell_compatibility_test $(ALL_PROGRAMS) $(LANG_BINDINGS) $(OTHER_PROGRAMS) tests-tools-targets > > > > # Create python binding output directory if not already present > > _dummy := $(shell [ -d '$(OUTPUT)python' ] || mkdir -p '$(OUTPUT)python') > > @@ -1020,6 +1028,7 @@ install-tests: all install-gtk > > $(INSTALL) tests/shell/*.sh '$(DESTDIR_SQ)$(perfexec_instdir_SQ)/tests/shell'; \ > > $(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(perfexec_instdir_SQ)/tests/shell/lib'; \ > > $(INSTALL) tests/shell/lib/*.sh '$(DESTDIR_SQ)$(perfexec_instdir_SQ)/tests/shell/lib' > > + $(Q)$(MAKE) -C tests/shell/tools install-tests > > > > install-bin: install-tools install-tests install-traceevent-plugins > > > > @@ -1088,7 +1097,7 @@ endif # BUILD_BPF_SKEL > > bpf-skel-clean: > > $(call QUIET_CLEAN, bpf-skel) $(RM) -r $(SKEL_TMP_OUT) $(SKELETONS) > > > > -clean:: $(LIBTRACEEVENT)-clean $(LIBAPI)-clean $(LIBBPF)-clean $(LIBSUBCMD)-clean $(LIBPERF)-clean fixdep-clean python-clean bpf-skel-clean > > +clean:: $(LIBTRACEEVENT)-clean $(LIBAPI)-clean $(LIBBPF)-clean $(LIBSUBCMD)-clean $(LIBPERF)-clean fixdep-clean python-clean bpf-skel-clean tests-tools-targets-clean > > $(call QUIET_CLEAN, core-objs) $(RM) $(LIBPERF_A) $(OUTPUT)perf-archive $(OUTPUT)perf-with-kcore $(OUTPUT)perf-iostat $(LANG_BINDINGS) > > $(Q)find $(if $(OUTPUT),$(OUTPUT),.) -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete > > $(Q)$(RM) $(OUTPUT).config-detected > > @@ -1155,5 +1164,6 @@ FORCE: > > .PHONY: shell_compatibility_test please_set_SHELL_PATH_to_a_more_modern_shell > > .PHONY: $(GIT-HEAD-PHONY) TAGS tags cscope FORCE prepare > > .PHONY: libtraceevent_plugins archheaders > > +.PHONY: $(TESTS_TOOLS_TARGETS) > > > > endif # force_fixdep > > diff --git a/tools/perf/tests/shell/coresight_asm_pure_loop.sh b/tools/perf/tests/shell/coresight_asm_pure_loop.sh > > new file mode 100755 > > index 000000000000..542d4a37e349 > > --- /dev/null > > +++ b/tools/perf/tests/shell/coresight_asm_pure_loop.sh > > @@ -0,0 +1,18 @@ > > +#!/bin/sh -e > > +# Coresight / ASM Pure Loop > > + > > +# SPDX-License-Identifier: GPL-2.0 > > +# Carsten Haitzler , 2021 > > + > > +TEST="asm_pure_loop" > > +. $(dirname $0)/lib/coresight.sh > > +ARGS="" > > +DATV="out" > > +DATA="$DATD/perf-$TEST-$DATV.data" > > + > > +perf record $PERFRECOPT -o "$DATA" "$BIN" $ARGS > > Is $ARGS redundant and can be removed? > > > +perf_dump_aux_verify "$DATA" 2601 334 334 > > These three magic numbers "2601 334 334" would be hard to understand. > One way is the code can dynamically calculate these values based on the > loop times (the loop is is predefined in asm_pure_loop.S), or it's > good to give explanation in comments for these values. > > > + > > +err=$? > > +exit $err > > diff --git a/tools/perf/tests/shell/lib/coresight.sh b/tools/perf/tests/shell/lib/coresight.sh > > new file mode 100644 > > index 000000000000..cd6c1283e6f5 > > --- /dev/null > > +++ b/tools/perf/tests/shell/lib/coresight.sh > > @@ -0,0 +1,130 @@ > > +# SPDX-License-Identifier: GPL-2.0 > > +# Carsten Haitzler , 2021 > > + > > +# This is sourced from a driver script so no need for #!/bin... etc. at the > > +# top - the assumption below is that it runs as part of sourcing after the > > +# test sets up some basic env vars to say what it is. > > + > > +# perf record options for the perf tests to use > > +PERFRECMEM="-m ,128M" > > We must use 128Mb for the AUX trace buffer? The big buffer size is > not friendly for embedded system. > > > +PERFRECOPT="$PERFRECMEM -e cs_etm//u" > > + > > +# These tests need to be run as root or coresight won't allow large buffers > > +# and will not collect proper data > > +UID=`id -u` > > +if test "$UID" -ne 0; then > > + echo "Not running as root... skip" > > + exit 2 > > +fi > > + > > +TOOLS=$(dirname $0)/tools > > +DIR="$TOOLS/coresight/$TEST" > > +BIN="$DIR/$TEST" > > +# If the test tool/binary does not exist and is executable then skip the test > > +if ! test -x "$BIN"; then exit 2; fi > > +DATD="." > > It's blur to set DATD and STATD to ".". If the user doesn't specify > the envs, it's not clear it will point to which folder. > > > +# If the data dir env is set then make the data dir use that instead of ./ > > +if test -n "$PERF_TEST_CORESIGHT_DATADIR"; then > > + DATD="$PERF_TEST_CORESIGHT_DATADIR"; > > +fi > > +# If the stat dir env is set then make the data dir use that instead of ./ > > +STATD="." > > +if test -n "$PERF_TEST_CORESIGHT_STATDIR"; then > > + STATD="$PERF_TEST_CORESIGHT_STATDIR"; > > +fi > > + > > +# Called if the test fails - error code 2 > > +err() { > > + echo "$1" > > + exit 1 > > +} > > + > > +# Check that some statistics from our perf > > +check_val_min() { > > + STATF="$4" > > + if test "$2" -lt "$3"; then > > + echo ", FAILED" >> "$STATF" > > + err "Sanity check number of $1 is too low ($2 < $3)" > > + fi > > +} > > + > > +perf_dump_aux_verify() { > > + # Some basic checking that the AUX chunk contains some sensible data > > + # to see that we are recording something and at least a minimum > > + # amount of it. We should almost always see F3 atoms in just about > > + # anything but certainly we will see some trace info and async atom > > + # chunks. > > + DUMP="$DATD/perf-tmp-aux-dump.txt" > > + perf report --stdio --dump -i "$1" | \ > > + grep -o -e I_ATOM_F3 -e I_ASYNC -e I_TRACE_INFO > "$DUMP" > > + # Simply count how many of these atoms we find to see that we are > > + # producing a reasonable amount of data - exact checks are not sane > > + # as this is a lossy process where we may lose some blocks and the > > + # compiler may produce different code depending on the compiler and > > + # optimization options, so this is rough just to see if we're > > + # either missing almost all the data or all of it > > + ATOM_F3_NUM=`grep I_ATOM_F3 "$DUMP" | wc -l` > > + ATOM_ASYNC_NUM=`grep I_ASYNC "$DUMP" | wc -l` > > + ATOM_TRACE_INFO_NUM=`grep I_TRACE_INFO "$DUMP" | wc -l` > > + rm -f "$DUMP" > > + > > + # Arguments provide minimums for a pass > > + CHECK_F3_MIN="$2" > > + CHECK_ASYNC_MIN="$3" > > + CHECK_TRACE_INFO_MIN="$4" > > + > > + # Write out statistics, so over time you can track results to see if > > + # there is a pattern - for example we have less "noisy" results that > > + # produce more consistent amounts of data each run, to see if over > > + # time any techinques to minimize data loss are having an effect or > > + # not > > + STATF="$STATD/stats-$TEST-$DATV.csv" > > + if ! test -f "$STATF"; then > > + echo "ATOM F3 Count, Minimum, ATOM ASYNC Count, Minimum, TRACE INFO Count, Minimum" > "$STATF" > > + fi > > + echo -n "$ATOM_F3_NUM, $CHECK_F3_MIN, $ATOM_ASYNC_NUM, $CHECK_ASYNC_MIN, $ATOM_TRACE_INFO_NUM, $CHECK_TRACE_INFO_MIN" >> "$STATF" > > + > > + # Actually check to see if we passed or failed. > > + check_val_min "ATOM_F3" "$ATOM_F3_NUM" "$CHECK_F3_MIN" "$STATF" > > + check_val_min "ASYNC" "$ATOM_ASYNC_NUM" "$CHECK_ASYNC_MIN" "$STATF" > > + check_val_min "TRACE_INFO" "$ATOM_TRACE_INFO_NUM" "$CHECK_TRACE_INFO_MIN" "$STATF" > > + echo ", Ok" >> "$STATF" > > +} > > + > > +perf_dump_aux_tid_verify() { > > This function is not used in the test contained in this patch. > > > + # Specifically crafted test will produce a list of Tread ID's to > > + # stdout that need to be checked to see that they have had trace > > + # info collected in AUX blocks in the perf data. This will go > > + # through all the TID's that are listed as CID=0xabcdef and see > > + # that all the Thread IDs the test tool reports are in the perf > > + # data AUX chunks > > + > > + # The TID test tools will print a TID per stdout line that are being > > + # tested > > + TIDS=`cat "$2"` > > + # Scan the perf report to find the TIDs that are actually CID in hex > > + # and build a list of the ones found > > + FOUND_TIDS=`perf report --stdio --dump -i "$1" | \ > > + grep -o "CID=0x[0-9a-z]\+" | sed 's/CID=//g' | \ > > + uniq | sort | uniq` > > + > > + # Iterate over the list of TIDs that the test says it has and find > > + # them in the TIDs found in the perf report > > + MISSING="" > > + for TID2 in $TIDS; do > > + FOUND="" > > + for TIDHEX in $FOUND_TIDS; do > > + TID=`printf "%i" $TIDHEX` > > + if test "$TID" -eq "$TID2"; then > > + FOUND="y" > > + break > > + fi > > + done > > + if test -z "$FOUND"; then > > + MISSING="$MISSING $TID" > > + fi > > + done > > + if test -n "$MISSING"; then > > + err "Thread IDs $MISSING not found in perf AUX data" > > + fi > > +} > > diff --git a/tools/perf/tests/shell/tools/Makefile b/tools/perf/tests/shell/tools/Makefile > > new file mode 100644 > > index 000000000000..c7ada20922fd > > --- /dev/null > > +++ b/tools/perf/tests/shell/tools/Makefile > > @@ -0,0 +1,26 @@ > > +# SPDX-License-Identifier: GPL-2.0-only > > +# Carsten Haitzler , 2021 > > +include ../../../../../tools/scripts/Makefile.include > > +include ../../../../../tools/scripts/Makefile.arch > > +include ../../../../../tools/scripts/utilities.mak > > To be honest, I don't understand well for perf's build and config > system. Seems to me, a good example for building program is jevents. > > Please take a look for the code: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/Makefile.perf#n667 > > If follow the same method with jevents for building test programs, > I can see one benefit is we don't need to create a Makefile, on the > other hand, we can reuse the perf's build system and simply create a > Build file under the folder tools/perf/tests/shell/.../coresight/. > > > + > > +SUBDIRS = \ > > + coresight > > + > > +all: $(SUBDIRS) > > +$(SUBDIRS): > > + $(Q)$(MAKE) -C $@ > > + > > +INSTALLDIRS = $(SUBDIRS:%=install-%) > > + > > +install-tests: all $(INSTALLDIRS) > > +$(INSTALLDIRS): > > + $(Q)$(MAKE) -C $(@:install-%=%) install-tests > > + > > +CLEANDIRS = $(SUBDIRS:%=clean-%) > > + > > +clean: $(CLEANDIRS) > > +$(CLEANDIRS): > > + $(Q)$(MAKE) -C $(@:clean-%=%) O=$(OUTPUT) clean >/dev/null > > + > > +.PHONY: all clean install-tests $(SUBDIRS) $(CLEANDIRS) $(INSTALLDIRS) > > diff --git a/tools/perf/tests/shell/tools/coresight/Makefile b/tools/perf/tests/shell/tools/coresight/Makefile > > new file mode 100644 > > index 000000000000..723006ea827c > > --- /dev/null > > +++ b/tools/perf/tests/shell/tools/coresight/Makefile > > @@ -0,0 +1,27 @@ > > +# SPDX-License-Identifier: GPL-2.0-only > > +# Carsten Haitzler , 2021 > > +include ../../../../../../tools/scripts/Makefile.include > > +include ../../../../../../tools/scripts/Makefile.arch > > +include ../../../../../../tools/scripts/utilities.mak > > + > > +SUBDIRS = \ > > + asm_pure_loop > > + > > +all: $(SUBDIRS) > > +$(SUBDIRS): > > + $(Q)$(MAKE) -C $@ > > + > > +INSTALLDIRS = $(SUBDIRS:%=install-%) > > + > > +install-tests: $(INSTALLDIRS) > > +$(INSTALLDIRS): > > + $(Q)$(MAKE) -C $(@:install-%=%) install-tests > > + > > +CLEANDIRS = $(SUBDIRS:%=clean-%) > > + > > +clean: $(CLEANDIRS) > > +$(CLEANDIRS): > > + $(Q)$(MAKE) -C $(@:clean-%=%) clean >/dev/null > > + > > +.PHONY: all clean $(SUBDIRS) $(CLEANDIRS) $(INSTALLDIRS) > > + > > diff --git a/tools/perf/tests/shell/tools/coresight/Makefile.miniconfig b/tools/perf/tests/shell/tools/coresight/Makefile.miniconfig > > new file mode 100644 > > index 000000000000..cedd26c6a0eb > > --- /dev/null > > +++ b/tools/perf/tests/shell/tools/coresight/Makefile.miniconfig > > @@ -0,0 +1,23 @@ > > +# SPDX-License-Identifier: GPL-2.0-only > > +# Carsten Haitzler , 2021 > > + > > +ifndef DESTDIR > > +prefix ?= $(HOME) > > +endif > > + > > +DESTDIR_SQ = $(subst ','\'',$(DESTDIR)) > > +perfexecdir = libexec/perf-core > > +perfexec_instdir = $(perfexecdir) > > + > > +ifneq ($(filter /%,$(firstword $(perfexecdir))),) > > +perfexec_instdir = $(perfexecdir) > > +else > > +perfexec_instdir = $(prefix)/$(perfexecdir) > > +endif > > + > > +perfexec_instdir_SQ = $(subst ','\'',$(perfexec_instdir)) > > +INSTALL = install > > + > > +include ../../../../../../scripts/Makefile.include > > +include ../../../../../../scripts/Makefile.arch > > +include ../../../../../../scripts/utilities.mak > > As suggested above, if we refer the building method of jevent, I think > this Makefile.miniconfig is not needed anymore. > > > diff --git a/tools/perf/tests/shell/tools/coresight/asm_pure_loop/Makefile b/tools/perf/tests/shell/tools/coresight/asm_pure_loop/Makefile > > new file mode 100644 > > index 000000000000..10c5a60cb71c > > --- /dev/null > > +++ b/tools/perf/tests/shell/tools/coresight/asm_pure_loop/Makefile > > @@ -0,0 +1,30 @@ > > +# SPDX-License-Identifier: GPL-2.0 > > +# Carsten Haitzler , 2021 > > + > > +include ../Makefile.miniconfig > > + > > +BIN=asm_pure_loop > > +LIB= > > + > > +all: $(BIN) > > + > > +$(BIN): $(BIN).S > > +ifdef CORESIGHT > > +ifeq ($(ARCH),arm64) > > + $(Q)$(CC) $(BIN).S -nostdlib -static -o $(BIN) $(LIB) > > +endif > > +endif > > + > > +install-tests: all > > +ifdef CORESIGHT > > +ifeq ($(ARCH),arm64) > > + $(call QUIET_INSTALL, tests) \ > > + $(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(perfexec_instdir_SQ)/tests/shell/tools/$(BIN)'; \ > > + $(INSTALL) $(BIN) '$(DESTDIR_SQ)$(perfexec_instdir_SQ)/tests/shell/tools/$(BIN)/$(BIN)' > > +endif > > +endif > > + > > +clean: > > + $(Q)$(RM) -f $(BIN) > > + > > +.PHONY: all clean install-tests > > diff --git a/tools/perf/tests/shell/tools/coresight/asm_pure_loop/asm_pure_loop.S b/tools/perf/tests/shell/tools/coresight/asm_pure_loop/asm_pure_loop.S > > new file mode 100644 > > index 000000000000..262876451021 > > --- /dev/null > > +++ b/tools/perf/tests/shell/tools/coresight/asm_pure_loop/asm_pure_loop.S > > @@ -0,0 +1,28 @@ > > +/* SPDX-License-Identifier: GPL-2.0 */ > > +/* Tamas Zsoldos , 2021 */ > > + > > +.globl _start > > +_start: > > + mov x0, 0x000fffff > > + mov x1, xzr > > +loop: > > + nop > > + nop > > + cbnz x1, noskip > > + nop > > + nop > > + adrp x2, skip > > + add x2, x2, :lo12:skip > > + br x2 > > + nop > > + nop > > +noskip: > > + nop > > + nop > > +skip: > > + sub x0, x0, 1 > > + cbnz x0, loop > > + > > + mov x0, #0 > > + mov x8, #93 // __NR_exit syscall > > + svc #0 > > I verified this code on Arm64 machine and it works! > > I am a bit worry about the code for using the hard code number for > system call. Another option is to use the inline assembly > in C code, I think you have considered for this approach, this might > introduce noise for extra branch instructions during the testing, > but it can allow us to program standard C program (and don't worry > about the program exiting). > > If you think using assembly code is better than inline assembly, it > would be fine for me. Eventually, the system call number is very > seldomly to be changed. > > Thanks, > Leo -- - Arnaldo