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Subject: Re: [RFC PATCH 04/10] perf workqueue: add threadpool execute and
 wait functions
From:   Riccardo Mancini <rickyman7@gmail.com>
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Ian Rogers <irogers@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Jiri Olsa <jolsa@redhat.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-perf-users <linux-perf-users@vger.kernel.org>
Date:   Fri, 16 Jul 2021 15:55:39 +0200
In-Reply-To: <CAM9d7ci9vCBsyYAj6kXUAtEufG9PW0D=1-7PP-VrA_PPU6wbkA@mail.gmail.com>
References: <cover.1626177381.git.rickyman7@gmail.com>
         <a5fee5068f9630f14f1f5c259434badf43d451c4.1626177381.git.rickyman7@gmail.com>
         <CAM9d7ci9vCBsyYAj6kXUAtEufG9PW0D=1-7PP-VrA_PPU6wbkA@mail.gmail.com>
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Hi Namhyung,
thanks again for the review.

On Thu, 2021-07-15 at 16:56 -0700, Namhyung Kim wrote:
> On Tue, Jul 13, 2021 at 5:11 AM Riccardo Mancini <rickyman7@gmail.com> wrote:
> > 
> > This patch adds:
> >  - execute_in_threadpool: assigns a task to the threads to execute
> >    asynchronously.
> >  - wait_threadpool: waits for the task to complete on all threads.
> > Furthermore, testing for these new functions is added.
> > 
> > This patch completes the threadpool.
> > 
> > Signed-off-by: Riccardo Mancini <rickyman7@gmail.com>
> > ---
> >  tools/perf/tests/workqueue.c           |  86 ++++++++++++++++++++-
> >  tools/perf/util/workqueue/threadpool.c | 103 +++++++++++++++++++++++++
> >  tools/perf/util/workqueue/threadpool.h |   5 ++
> >  3 files changed, 193 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/tests/workqueue.c b/tools/perf/tests/workqueue.c
> > index be377e9897bab4e9..3c64db8203556847 100644
> > --- a/tools/perf/tests/workqueue.c
> > +++ b/tools/perf/tests/workqueue.c
> > @@ -1,13 +1,59 @@
> >  // SPDX-License-Identifier: GPL-2.0
> > +#include <stdlib.h>
> >  #include <linux/kernel.h>
> > +#include <linux/zalloc.h>
> >  #include "tests.h"
> >  #include "util/debug.h"
> >  #include "util/workqueue/threadpool.h"
> > 
> > +#define DUMMY_FACTOR 100000
> > +#define N_DUMMY_WORK_SIZES 7
> > +
> >  struct threadpool_test_args_t {
> >         int pool_size;
> >  };
> > 
> > +struct test_task {
> > +       struct task_struct task;
> > +       int n_threads;
> > +       int *array;
> > +};
> > +
> > +/**
> > + * dummy_work - calculates DUMMY_FACTOR * (idx % N_DUMMY_WORK_SIZES)
> > inefficiently
> > + *
> > + * This function uses modulus to create work items of different sizes.
> > + */
> > +static void dummy_work(int idx)
> > +{
> > +       int prod = 0;
> 
> I'm not sure but having 'volatile' would prevent some kind of
> possible compiler optimizations..

Agreed.

> 
> > +       int k = idx % N_DUMMY_WORK_SIZES;
> > +       int i, j;
> > +
> > +       for (i = 0; i < DUMMY_FACTOR; i++)
> > +               for (j = 0; j < k; j++)
> > +                       prod ++;
> > +
> > +       pr_debug3("dummy: %d * %d = %d\n", DUMMY_FACTOR, k, prod);
> > +}
> > +
> > +static void test_task_fn1(int tidx, struct task_struct *task)
> > +{
> > +       struct test_task *mtask = container_of(task, struct test_task,
> > task);
> > +
> > +       dummy_work(tidx);
> > +       mtask->array[tidx] = tidx+1;
> > +}
> > +
> > +static void test_task_fn2(int tidx, struct task_struct *task)
> > +{
> > +       struct test_task *mtask = container_of(task, struct test_task,
> > task);
> > +
> > +       dummy_work(tidx);
> > +       mtask->array[tidx] = tidx*2;
> > +}
> > +
> > +
> >  static int __threadpool__prepare(struct threadpool_struct **pool, int
> > pool_size)
> >  {
> >         int ret;
> > @@ -38,21 +84,59 @@ static int __threadpool__teardown(struct
> > threadpool_struct *pool)
> >         return 0;
> >  }
> > 
> > +static int __threadpool__exec_wait(struct threadpool_struct *pool,
> > +                               struct task_struct *task)
> > +{
> > +       int ret;
> > +
> > +       ret = execute_in_threadpool(pool, task);
> > +       TEST_ASSERT_VAL("threadpool execute failure", ret == 0);
> > +       TEST_ASSERT_VAL("threadpool is not executing",
> > threadpool_is_busy(pool));
> > +
> > +       ret = wait_threadpool(pool);
> > +       TEST_ASSERT_VAL("threadpool wait failure", ret == 0);
> > +       TEST_ASSERT_VAL("waited threadpool is not ready",
> > threadpool_is_ready(pool));
> > +
> > +       return 0;
> > +}
> > 
> >  static int __test__threadpool(void *_args)
> >  {
> >         struct threadpool_test_args_t *args = _args;
> >         struct threadpool_struct *pool;
> > -       int ret;
> > +       int ret, i;
> > +       struct test_task task;
> > +
> > +       task.task.fn = test_task_fn1;
> > +       task.n_threads = args->pool_size;
> > +       task.array = calloc(args->pool_size, sizeof(*task.array));
> 
> Need to check the return value.

Thanks.

> 
> > 
> >         ret = __threadpool__prepare(&pool, args->pool_size);
> >         if (ret)
> >                 return ret;
> > 
> > +       ret = __threadpool__exec_wait(pool, &task.task);
> > +       if (ret)
> > +               return ret;
> > +
> > +       for (i = 0; i < args->pool_size; i++)
> > +               TEST_ASSERT_VAL("failed array check (1)", task.array[i] ==
> > i+1);
> > +
> > +       task.task.fn = test_task_fn2;
> > +
> > +       ret = __threadpool__exec_wait(pool, &task.task);
> > +       if (ret)
> > +               return ret;
> > +
> > +       for (i = 0; i < args->pool_size; i++)
> > +               TEST_ASSERT_VAL("failed array check (2)", task.array[i] ==
> > 2*i);
> > +
> >         ret = __threadpool__teardown(pool);
> >         if (ret)
> >                 return ret;
> > 
> > +       free(task.array);
> 
> All previous returns will leak it.

Oh, right.

Thanks,
Riccardo

> 
> Thanks,
> Namhyung