From: Alexander Potapenko <glider@google.com>
To: vjitta@codeaurora.org
Cc: Minchan Kim <minchan@kernel.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
dan.j.williams@intel.com, broonie@kernel.org,
Masami Hiramatsu <mhiramat@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Andrey Konovalov <andreyknvl@google.com>,
qcai@redhat.com, ylal@codeaurora.org, vinmenon@codeaurora.org
Subject: Re: [PATCH v3] lib: stackdepot: Add support to configure STACK_HASH_SIZE
Date: Fri, 11 Dec 2020 09:36:04 +0100 [thread overview]
Message-ID: <CAG_fn=VKsrYx+YOGPnZw_Q5t6Fx7B59FSUuphj7Ou+DDFKQ+8Q@mail.gmail.com> (raw)
In-Reply-To: <1607576401-25609-1-git-send-email-vjitta@codeaurora.org>
On Thu, Dec 10, 2020 at 6:01 AM <vjitta@codeaurora.org> wrote:
>
> From: Yogesh Lal <ylal@codeaurora.org>
>
> Add a kernel parameter stack_hash_order to configure STACK_HASH_SIZE.
>
> Aim is to have configurable value for STACK_HASH_SIZE, so that one
> can configure it depending on usecase there by reducing the static
> memory overhead.
>
> One example is of Page Owner, default value of STACK_HASH_SIZE lead
> stack depot to consume 8MB of static memory. Making it configurable
> and use lower value helps to enable features like CONFIG_PAGE_OWNER
> without any significant overhead.
Can we go with a static CONFIG_ parameter instead?
Guess most users won't bother changing the default anyway, and for
CONFIG_PAGE_OWNER users changing the size at boot time is not strictly
needed.
> -static struct stack_record *stack_table[STACK_HASH_SIZE] = {
> - [0 ... STACK_HASH_SIZE - 1] = NULL
> +static unsigned int stack_hash_order = 20;
Please initialize with MAX_STACK_HASH_ORDER instead.
> +static struct stack_record *stack_table_def[MAX_STACK_HASH_SIZE] __initdata = {
> + [0 ... MAX_STACK_HASH_SIZE - 1] = NULL
> };
> +static struct stack_record **stack_table __refdata = stack_table_def;
> +
> +static int __init setup_stack_hash_order(char *str)
> +{
> + kstrtouint(str, 0, &stack_hash_order);
> + if (stack_hash_order > MAX_STACK_HASH_ORDER)
> + stack_hash_order = MAX_STACK_HASH_ORDER;
> + return 0;
> +}
> +early_param("stack_hash_order", setup_stack_hash_order);
> +
> +static int __init init_stackdepot(void)
> +{
> + size_t size = (STACK_HASH_SIZE * sizeof(struct stack_record *));
> +
> + stack_table = vmalloc(size);
> + memcpy(stack_table, stack_table_def, size);
Looks like you are assuming stack_table_def already contains some data
by this point.
But if STACK_HASH_SIZE shrinks this memcpy() above will just copy some
part of the table, whereas the rest will be lost.
We'll need to:
- either explicitly decide we can afford losing this data (no idea how
bad this can potentially be),
- or disallow storing anything prior to full stackdepot initialization
(then we don't need stack_table_def),
- or carefully move all entries to the first part of the table.
Alex
next prev parent reply other threads:[~2020-12-11 8:38 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-10 5:00 [PATCH v3] lib: stackdepot: Add support to configure STACK_HASH_SIZE vjitta
2020-12-11 8:36 ` Alexander Potapenko [this message]
2020-12-11 12:45 ` Vijayanand Jitta
2020-12-11 13:25 ` Alexander Potapenko
2020-12-14 4:02 ` Vijayanand Jitta
2020-12-14 9:34 ` Alexander Potapenko
2020-12-14 10:32 ` Vijayanand Jitta
2020-12-16 3:43 ` Vijayanand Jitta
2020-12-16 8:26 ` Alexander Potapenko
2020-12-16 13:06 ` Vijayanand Jitta
2020-12-16 13:11 ` Alexander Potapenko
2020-12-16 13:22 ` Vijayanand Jitta
2020-12-16 13:34 ` Alexander Potapenko
2020-12-17 5:38 ` Vijayanand Jitta
2020-12-17 10:19 ` Dmitry Vyukov
2020-12-17 10:54 ` Alexander Potapenko
2020-12-18 8:40 ` Vijayanand Jitta
2020-12-21 11:14 ` Vijayanand Jitta
2020-12-21 15:04 ` Alexander Potapenko
2020-12-21 20:29 ` Minchan Kim
2020-12-22 5:55 ` Vijayanand Jitta
2020-12-23 14:40 ` Alexander Potapenko
2020-12-28 4:51 ` Vijayanand Jitta
2020-12-15 9:34 ` [lib] 1333d0ba67: WARNING:at_kernel/locking/lockdep.c:#lockdep_register_key kernel test robot
2020-12-17 10:25 ` [PATCH v3] lib: stackdepot: Add support to configure STACK_HASH_SIZE Dmitry Vyukov
2020-12-17 10:27 ` Dmitry Vyukov
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