From: Andrew Morton <akpm@linux-foundation.org>
To: vjitta@codeaurora.org
Cc: minchan@kernel.org, glider@google.com, dan.j.williams@intel.com,
broonie@kernel.org, mhiramat@kernel.org,
linux-kernel@vger.kernel.org, ylal@codeaurora.org,
vinmenon@codeaurora.org, Thomas Gleixner <tglx@linutronix.de>,
Alexander Potapenko <glider@google.com>
Subject: Re: [PATCH v4 1/2] lib: stackdepot: Add support to configure STACK_HASH_SIZE
Date: Mon, 4 Jan 2021 15:12:23 -0800 [thread overview]
Message-ID: <20210104151223.34f97a033e966c9cc89915cb@linux-foundation.org> (raw)
In-Reply-To: <1609332331-2456-1-git-send-email-vjitta@codeaurora.org>
On Wed, 30 Dec 2020 18:15:30 +0530 vjitta@codeaurora.org wrote:
> Use STACK_HASH_ORDER_SHIFT to configure STACK_HASH_SIZE.
>
> Aim is to have configurable value for STACK_HASH_SIZE,
> so depend on use case one can configure it.
>
> 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.
Questions regarding the stackdepot code.
- stack_table_tmp[] is __initdata. So after initmem is released,
that "consume 8MB of static memory" should no longer be true. But
iirc, not all architectures actually release __initdata memory. Does
your architecture do this?
- Stackdepot copies stack_table_tmp[] into vmalloced memory during
initcalls. Why? Why not simply make stack_table_tmp[] no longer
__initdata and use that memory for all time?
Presumably because in the stack_depot_disable==true case, we
release stack_table_tmp[] memory, don't vmalloc for a copy of it, and
save a bunch of memory? If so, this assumes that the __initdata
memory is freed.
- Why is that hash table so large? Is it appropriately sized?
- SMP is up and running during init_stackdepot(), I think? If so, is
that huge memcpy smp-safe? Can other CPUs be modifying
stack_table_tmp[] while the memcpy is in flight?
next prev parent reply other threads:[~2021-01-04 23:13 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-30 12:45 vjitta
2020-12-30 12:45 ` [PATCH v4 2/2] lib: stackdepot: Add support to disable stack depot vjitta
2021-01-04 23:12 ` Andrew Morton [this message]
2021-01-05 9:24 ` [PATCH v4 1/2] lib: stackdepot: Add support to configure STACK_HASH_SIZE Vijayanand Jitta
2021-01-19 4:02 ` Vijayanand Jitta
2021-01-07 9:44 ` Alexander Potapenko
2021-01-18 11:14 ` Vijayanand Jitta
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