From: DaeRo Lee <skseofh@gmail.com>
To: Mike Rapoport <rppt@kernel.org>
Cc: robh@kernel.org, saravanak@google.com, akpm@linux-foundation.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Daero Lee <daero_le.lee@samsung.com>,
richard.weiyang@gmail.com
Subject: Re: [PATCH v2] memblock: add no-map alloc functions
Date: Sat, 27 Apr 2024 11:42:26 +0900 [thread overview]
Message-ID: <CAATEi5n-JxfLCKom2y6pPY-MKzN90p9f5gkEpxD4652jUDKJ8Q@mail.gmail.com> (raw)
In-Reply-To: <CAATEi5ksY-v7-LEqNZWFV5hsHiegNEtrh4LpMWOQ=vT7hC0Rng@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 3925 bytes --]
2024년 4월 19일 (금) 오전 10:59, DaeRo Lee <skseofh@gmail.com>님이 작성:
> 2024년 4월 19일 (금) 오전 10:46, DaeRo Lee <skseofh@gmail.com>님이 작성:
> >
> > 2024년 4월 19일 (금) 오전 3:04, Mike Rapoport <rppt@kernel.org>님이 작성:
> > >
> > > On Thu, Apr 18, 2024 at 11:54:15PM +0900, DaeRo Lee wrote:
> > > > 2024년 4월 17일 (수) 오후 3:03, Mike Rapoport <rppt@kernel.org>님이 작성:
> > > > >
> > > > > On Tue, Apr 16, 2024 at 09:06:35PM +0900, skseofh@gmail.com wrote:
> > > > > > From: Daero Lee <daero_le.lee@samsung.com>
> > > > > >
> > > > > > Like reserved-memory with the 'no-map' property and only 'size'
> property
> > > > > > (w/o 'reg' property), there are memory regions need to be
> allocated in
> > > > > > memblock.memory marked with the MEMBLOCK_NOMAP flag, but should
> not be
> > > > > > allocated in memblock.reserved.
> > > > >
> > > > > This still does not explain why you need such regions.
> > > > >
> > > > > As Wei Yang explained, memblock does not allocate memory from
> > > > > memblock.reserved. The memblock.reserved array represents memory
> that is in
> > > > > use by firmware or by early kernel allocations and cannot be freed
> to page
> > > > > allocator.
> > > > Thank you for your comments. I used the wrong word.
> > > > When I use 'allocate', I mean that the region 'adds' to the
> memblock.reserved.
> > > >
> > > > >
> > > > > If you have a region that's _NOMAP in memblock.memory and is
> absent in
> > > > > memblock.reserved it will not be mapped by the kernel page tables,
> but it
> > > > > will be considered as free memory by the core mm.
> > > > >
> > > > > Is this really what you want?
> > > > If my understanding is right, before freeing (memory && !reserved)
> > > > area, we marked the memblock.reserved regions and memblock.memory
> > > > regions with no-map flag. And when we free (memory && !reserved)
> area,
> > > > we skip the memblock.memory regions with no-map(see
> > > > should_skip_region). So, I think that the memory regions with no-map
> > > > flag will not be considered as free memory.
> > >
> > > You are right here.
> > >
> > > But I still don't understand *why* do you want to change the way
> > > early_init_dt_alloc_reserved_memory_arch() works.
> >
> > In memmap_init_reserved_pages, we mark memblock.reserved as
> > PageReserved first and mark the memblock.reserved with nomap flag
> > also.
> Sorry. This is my mistake. 'memblock.memory with nomap flag' is right.
>
> > -> Isn't this duplicated work? (If we add no-map region to
> > memblock.reserved 'and' mark in memblock.memory..)
> > So, I think that for the no-map region, we don't need to add to the
> > memblock.reserved.
> > This is what we do now in early_init_dt_reserve_memory. the nomap
> > region is not added to the memblock.reserved.
> >
> > In early_init_dt_alloc_reserved_memory_arch, if 'nomap' is true, we
> > mark the memblock.memory region as _NOMAP. And if the return value
> > 'err' is not zero(which is '-ENOMEM' from memblock_isolate_range), we
> > free the region.
> > - 'nomap' is true -> memblock_mark_nomap : success -> not free the region
> >
> > : fail -> free the region
> > And it can be said that we add the region to the memblock.reserved
> > using memblock_phys_alloc_range and if the region is nomap, then we
> > can free the region from memblock.reserved. But is it necessary to add
> > it to memblock.reserved? We just need the region in memblock.memory to
> > mark nomap.
> >
> > So, here is what I think:
> > - reserved-memory w/ nomap region -> mark only to memblock.memory
> > - reserved-memory w/o nomap region -> add to the memblock.reserved
> >
> > Regards,
> > DaeRo Lee
>
Hello
Can I get your opinions about this?
It will be very helpful to improve my understanding of memblock and
reserved region.
Thank you
>
[-- Attachment #2: Type: text/html, Size: 5629 bytes --]
next prev parent reply other threads:[~2024-04-27 2:42 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-16 12:06 [PATCH v2] memblock: add no-map alloc functions skseofh
2024-04-16 12:06 ` skseofh
2024-04-17 2:23 ` Wei Yang
2024-04-17 6:02 ` Mike Rapoport
2024-04-18 14:54 ` DaeRo Lee
2024-04-18 18:03 ` Mike Rapoport
2024-04-19 1:46 ` DaeRo Lee
2024-04-19 1:59 ` DaeRo Lee
2024-04-27 2:42 ` DaeRo Lee [this message]
2024-04-27 3:27 ` DaeRo Lee
2024-04-27 8:49 ` Mike Rapoport
2024-04-27 10:24 ` DaeRo Lee
2024-04-28 6:33 ` Mike Rapoport
2024-04-28 10:36 ` DaeRo Lee
2024-04-28 12:00 ` Mike Rapoport
2024-04-28 12:52 ` DaeRo Lee
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAATEi5n-JxfLCKom2y6pPY-MKzN90p9f5gkEpxD4652jUDKJ8Q@mail.gmail.com \
--to=skseofh@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=daero_le.lee@samsung.com \
--cc=devicetree@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=richard.weiyang@gmail.com \
--cc=robh@kernel.org \
--cc=rppt@kernel.org \
--cc=saravanak@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.