From: Mike Rapoport <rppt@linux.ibm.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>,
Vlastimil Babka <vbabka@suse.cz>, Mel Gorman <mgorman@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, Qian Cai <cai@lca.pw>,
Michal Hocko <mhocko@kernel.org>,
linux-kernel@vger.kernel.org, Baoquan He <bhe@redhat.com>
Subject: Re: [PATCH 1/1] mm: compaction: avoid fast_isolate_around() to set pageblock_skip on reserved pages
Date: Thu, 26 Nov 2020 23:03:32 +0200 [thread overview]
Message-ID: <20201126210332.GV123287@linux.ibm.com> (raw)
In-Reply-To: <X8AQSViIvYKyEOF6@redhat.com>
On Thu, Nov 26, 2020 at 03:30:01PM -0500, Andrea Arcangeli wrote:
> On Thu, Nov 26, 2020 at 09:44:26PM +0200, Mike Rapoport wrote:
> > TBH, the whole interaction between e820 and memblock keeps me puzzled
> > and I can only make educated guesses why some ranges here are
> > memblock_reserve()'d and some memblock_add()ed.
>
> The mixed usage in that interaction between memblock.reserve and
> memblock.memory where sometime it's used to reserve overlapping
> memblock.memory ranges (clearly ok), and sometimes is used on ranges
> with no overlap (not clear even why it's being called), is what makes
> the current code messy.
>
> We're basically passing down the exact same information (inverted),
> through two different APIs, if there is no overlap.
>
> > I think what should be there is that e820 entries that are essentially
> > RAM, used by BIOS or not, should be listed in memblock.memory. Then
> > using memblock_reserve() for parts that BIOS claimed for itself would
> > have the same semantics as for memory allocated by kernel.
> >
> > I.e. if there is a DIMM from 0 to, say 512M, memblock.memory will have a
> > range [0, 512M]. And areas such as 0x000-0xfff, 0x9d000-0x9ffff will be
> > in memblock.reserved.
> >
> > Than in page_alloc.c we'll know that we have a physical memory bank from
> > 0 to 512M but there are some ranges that we cannot use.
> >
> > I suggested it back then when the issue with compaction was reported at
> > the first time, but Baoquan mentioned that there are systems that cannot
> > even tolerate having BIOS reserved areas in the page tables and I didn't
> > continue to pursue this.
>
> That explains why we can't add the e820 non-RAM regions to
> memblock_add, what's not clear is why it should be required to call
> memblock_reserve on a region that has no overlap with any memblock_add.
>
> Instead of the patch that adds a walk to the memblock.reserve and that
> requires adding even more memblock_reserve to e820__memblock_setup for
> type 20, we can add a walk for the memblock.memory holes and then we
> can remove the memblock_reserve for E820_TYPE_SOFT_RESERVED too.
This is more or less what I have done here:
https://lore.kernel.org/lkml/20201126174601.GT123287@linux.ibm.com/
just without the removal of the call to memblock_reserve() for
E820_TYPE_SOFT_RESERVED.
> Thanks,
> Andrea
>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2020-11-26 21:05 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-23 21:25 compaction: VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn)) Qian Cai
2020-04-24 3:43 ` Baoquan He
2020-04-24 13:45 ` Qian Cai
2020-05-05 12:43 ` Baoquan He
2020-05-05 13:20 ` Qian Cai
2020-05-11 1:21 ` Baoquan He
2020-04-26 14:41 ` Mike Rapoport
2020-04-27 13:45 ` Qian Cai
2020-11-21 19:45 ` [PATCH 0/1] VM_BUG_ON_PAGE(!zone_spans_pfn) in set_pfnblock_flags_mask Andrea Arcangeli
2020-11-21 19:45 ` [PATCH 1/1] mm: compaction: avoid fast_isolate_around() to set pageblock_skip on reserved pages Andrea Arcangeli
2020-11-21 19:53 ` Andrea Arcangeli
2020-11-23 11:26 ` David Hildenbrand
2020-11-23 13:01 ` Vlastimil Babka
2020-11-24 13:32 ` Mel Gorman
2020-11-24 20:56 ` Andrea Arcangeli
2020-11-25 10:30 ` Mel Gorman
2020-11-25 17:59 ` Andrea Arcangeli
2020-11-26 10:47 ` Mel Gorman
2020-12-06 2:26 ` Andrea Arcangeli
2020-12-06 23:47 ` Mel Gorman
2020-11-25 5:34 ` Andrea Arcangeli
2020-11-25 6:45 ` David Hildenbrand
2020-11-25 8:51 ` Mike Rapoport
2020-11-25 10:39 ` Mel Gorman
2020-11-25 11:04 ` David Hildenbrand
2020-11-25 11:41 ` David Hildenbrand
2020-11-25 18:47 ` Andrea Arcangeli
2020-11-25 13:33 ` Mel Gorman
2020-11-25 13:41 ` David Hildenbrand
2020-11-25 18:28 ` Andrea Arcangeli
2020-11-25 19:27 ` David Hildenbrand
2020-11-25 20:41 ` Andrea Arcangeli
2020-11-25 21:13 ` David Hildenbrand
2020-11-25 21:04 ` Mike Rapoport
2020-11-25 21:38 ` Andrea Arcangeli
2020-11-26 9:36 ` Mike Rapoport
2020-11-26 10:05 ` David Hildenbrand
2020-11-26 17:46 ` Mike Rapoport
2020-11-29 12:32 ` Mike Rapoport
2020-12-02 0:44 ` Andrea Arcangeli
2020-12-02 17:39 ` Mike Rapoport
2020-12-03 6:23 ` Andrea Arcangeli
2020-12-03 10:51 ` Mike Rapoport
2020-12-03 17:31 ` Andrea Arcangeli
2020-12-06 8:09 ` Mike Rapoport
2020-11-26 18:15 ` Andrea Arcangeli
2020-11-26 18:29 ` Andrea Arcangeli
2020-11-26 19:44 ` Mike Rapoport
2020-11-26 20:30 ` Andrea Arcangeli
2020-11-26 21:03 ` Mike Rapoport [this message]
2020-11-26 19:21 ` Andrea Arcangeli
2020-11-25 12:08 ` Vlastimil Babka
2020-11-25 13:32 ` David Hildenbrand
2020-11-25 14:13 ` Mike Rapoport
2020-11-25 14:42 ` David Hildenbrand
2020-11-26 10:51 ` Mel Gorman
2020-11-25 19:14 ` Andrea Arcangeli
2020-11-25 19:01 ` Andrea Arcangeli
2020-11-25 19:33 ` David Hildenbrand
2020-11-26 3:40 ` Andrea Arcangeli
2020-11-26 10:43 ` Mike Rapoport
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