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Message-Id: <20231212192218.54095-1-sj@kernel.org>
Date: Tue, 12 Dec 2023 19:22:18 +0000
From: SeongJae Park <sj@...nel.org>
To: SeongJae Park <sj@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Shuah Khan <shuah@...nel.org>, damon@...ts.linux.dev,
linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] selftests/damon: add a test for update_schemes_tried_regions sysfs command
This and fifth patch of this patchset may not cleanly applicable, since those
are made on top of my out-of-tree experimental changes. I will rebase these
and send v2. Sorry for the noise.
Thanks,
SJ
On 2023-12-12T19:12:05+00:00 SeongJae Park <sj@...nel.org> wrote:
> Add a selftest for verifying the accuracy of DAMON's access monitoring
> functionality. The test starts a program of artificial access pattern,
> monitor the access pattern using DAMON, and check if DAMON finds
> expected amount of hot data region (working set size) with only
> acceptable error rate.
>
> Note that the acceptable error rate is set with only naive assumptions
> and small number of tests. Hence failures of the test may not always
> mean DAMON is broken. Rather than that, those could be a signal to
> better understand the real accuracy level of DAMON in wider
> environments. Based on further finding, we could optimize DAMON or
> adjust the expectation of the test.
>
> Signed-off-by: SeongJae Park <sj@...nel.org>
> ---
> tools/testing/selftests/damon/Makefile | 2 +
> tools/testing/selftests/damon/access_memory.c | 41 ++++++++++++++
> ...te_schemes_tried_regions_wss_estimation.py | 55 +++++++++++++++++++
> 3 files changed, 98 insertions(+)
> create mode 100644 tools/testing/selftests/damon/access_memory.c
> create mode 100755 tools/testing/selftests/damon/sysfs_update_schemes_tried_regions_wss_estimation.py
>
> diff --git a/tools/testing/selftests/damon/Makefile b/tools/testing/selftests/damon/Makefile
> index d2105d41ea25..1363987709c6 100644
> --- a/tools/testing/selftests/damon/Makefile
> +++ b/tools/testing/selftests/damon/Makefile
> @@ -4,6 +4,7 @@
> TEST_GEN_FILES += huge_count_read_write
> TEST_GEN_FILES += dbgfs_target_ids_read_before_terminate_race
> TEST_GEN_FILES += dbgfs_target_ids_pid_leak
> +TEST_GEN_FILES += access_memory
>
> TEST_FILES = _chk_dependency.sh _debugfs_common.sh
> TEST_PROGS = debugfs_attrs.sh debugfs_schemes.sh debugfs_target_ids.sh
> @@ -11,6 +12,7 @@ TEST_PROGS += debugfs_empty_targets.sh debugfs_huge_count_read_write.sh
> TEST_PROGS += debugfs_duplicate_context_creation.sh
> TEST_PROGS += debugfs_rm_non_contexts.sh
> TEST_PROGS += sysfs.sh sysfs_update_removed_scheme_dir.sh
> +TEST_PROGS += sysfs_update_schemes_tried_regions_wss_estimation.py
> TEST_PROGS += reclaim.sh lru_sort.sh
> TEST_PROGS += dbgfs_target_ids_read_before_terminate_race.sh
> TEST_PROGS += dbgfs_target_ids_pid_leak.sh
> diff --git a/tools/testing/selftests/damon/access_memory.c b/tools/testing/selftests/damon/access_memory.c
> new file mode 100644
> index 000000000000..585a2fa54329
> --- /dev/null
> +++ b/tools/testing/selftests/damon/access_memory.c
> @@ -0,0 +1,41 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Artificial memory access program for testing DAMON.
> + */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <time.h>
> +
> +int main(int argc, char *argv[])
> +{
> + char **regions;
> + clock_t start_clock;
> + int nr_regions;
> + int sz_region;
> + int access_time_ms;
> + int i;
> +
> + if (argc != 4) {
> + printf("Usage: %s <number> <size (bytes)> <time (ms)>\n",
> + argv[0]);
> + return -1;
> + }
> +
> + nr_regions = atoi(argv[1]);
> + sz_region = atoi(argv[2]);
> + access_time_ms = atoi(argv[3]);
> +
> + regions = malloc(sizeof(*regions) * nr_regions);
> + for (i = 0; i < nr_regions; i++)
> + regions[i] = malloc(sz_region);
> +
> + for (i = 0; i < nr_regions; i++) {
> + start_clock = clock();
> + while ((clock() - start_clock) * 1000 / CLOCKS_PER_SEC <
> + access_time_ms)
> + memset(regions[i], i, 1024 * 1024 * 10);
> + }
> + return 0;
> +}
> diff --git a/tools/testing/selftests/damon/sysfs_update_schemes_tried_regions_wss_estimation.py b/tools/testing/selftests/damon/sysfs_update_schemes_tried_regions_wss_estimation.py
> new file mode 100755
> index 000000000000..cdbf19b442c9
> --- /dev/null
> +++ b/tools/testing/selftests/damon/sysfs_update_schemes_tried_regions_wss_estimation.py
> @@ -0,0 +1,55 @@
> +#!/usr/bin/env python3
> +# SPDX-License-Identifier: GPL-2.0
> +
> +import subprocess
> +import time
> +
> +import _damon_sysfs
> +
> +def main():
> + # access two 10 MiB memory regions, 2 second per each
> + sz_region = 10 * 1024 * 1024
> + proc = subprocess.Popen(['./access_memory', '2', '%d' % sz_region, '2000'])
> + kdamonds = _damon_sysfs.Kdamonds([_damon_sysfs.Kdamond(
> + contexts=[_damon_sysfs.DamonCtx(
> + ops='vaddr',
> + targets=[_damon_sysfs.DamonTarget(pid=proc.pid)],
> + schemes=[_damon_sysfs.Damos(
> + access_pattern=_damon_sysfs.DamosAccessPattern(
> + # >= 25% access rate, >= 200ms age
> + nr_accesses=[5, 20], age=[2, 2**64 - 1]))] # schemes
> + )] # contexts
> + )]) # kdamonds
> +
> + err = kdamonds.start()
> + if err != None:
> + print('kdmaond start failed: %s' % err)
> + exit(1)
> +
> + wss_collected = []
> + while proc.poll() == None:
> + time.sleep(0.1)
> + err = kdamonds.kdamonds[0].update_schemes_tried_bytes()
> + if err != None:
> + print('tried bytes update failed: %s' % err)
> + exit(1)
> +
> + wss_collected.append(
> + kdamonds.kdamonds[0].contexts[0].schemes[0].tried_bytes)
> +
> + wss_collected.sort()
> + acceptable_error_rate = 0.2
> + for percentile in [50, 75]:
> + sample = wss_collected[int(len(wss_collected) * percentile / 100)]
> + error_rate = abs(sample - sz_region) / sz_region
> + print('%d-th percentile (%d) error %f' %
> + (percentile, sample, error_rate))
> + if error_rate > acceptable_error_rate:
> + print('the error rate is not acceptable (> %f)' %
> + acceptable_error_rate)
> + print('samples are as below')
> + print('\n'.join(['%d' % wss for wss in wss_collected]))
> + exit(1)
> +
> +if __name__ == '__main__':
> + main()
> --
> 2.34.1
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