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Date:   Thu, 4 Aug 2022 00:34:38 -0500
From:   Rebecca Mckeever <remckee0@gmail.com>
To:     "Huang, Shaoqin" <shaoqin.huang@intel.com>
Cc:     Mike Rapoport <rppt@kernel.org>,
        Karolina Drobnik <karolinadrobnik@gmail.com>,
        David Hildenbrand <david@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] memblock test: Add test to memblock_add() 129th region
Message-ID: <YutabjAN+hJwUaoF@bertie>
References: <20220801064901.980558-1-shaoqin.huang@intel.com>
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 <4c8def19-650e-7bc3-a581-3ce2b7c0b3cf@intel.com>
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On Tue, Aug 02, 2022 at 03:38:37PM +0800, Huang, Shaoqin wrote:
> 
> 
> On 8/2/2022 3:15 PM, Mike Rapoport wrote:
> > On Mon, Aug 01, 2022 at 02:48:36PM +0800, shaoqin.huang@intel.com wrote:
> > > From: Shaoqin Huang <shaoqin.huang@intel.com>
> > > 
> > > Add 129th region into the memblock, and this will trigger the
> > > memblock_double_array() function, this needs valid memory regions. So
> > > using dummy_physical_memory_init() to allocate some valid memory, when
> > > memblock_double_array() choose a new memory region from memory.regions,
> > > it will always choose a valid memory region if we add all valid memory
> > > region, so the memblock_double_array() must success.
> > > 
> > > Another thing should be done is to restore the memory.regions after
> > > memblock_double_array(), due to now the memory.regions is pointing to a
> > > memory region allocated by dummy_physical_memory_init(). And it will
> > > affect the subsequent tests if we don't restore the memory region. So
> > > Simply record the origin region, and restore it after the test.
> > > 
> > > Signed-off-by: Shaoqin Huang <shaoqin.huang@intel.com>
> > > ---
> > > Changelog:
> > > ----------
> > > v2:
> > >    - Use ASSERT_EQ() to replace assert().
> > >    - Not to expose memory_block, and add a function get_memory_block_base() to
> > >    get the memory_block.base.
> > >    - Add two functions for common usage, and now it has been used by this patch
> > >    to allocate many valid memory regions and free them at the end.
> > > 
> > >   tools/testing/memblock/tests/basic_api.c | 54 ++++++++++++++++++++++++
> > >   tools/testing/memblock/tests/common.c    | 38 +++++++++++++++--
> > >   tools/testing/memblock/tests/common.h    |  6 +++
> > >   3 files changed, 95 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/tools/testing/memblock/tests/basic_api.c b/tools/testing/memblock/tests/basic_api.c
> > > index 66f46f261e66..46948d5a975e 100644
> > > --- a/tools/testing/memblock/tests/basic_api.c
> > > +++ b/tools/testing/memblock/tests/basic_api.c
> > > @@ -326,6 +326,59 @@ static int memblock_add_twice_check(void)
> > >   	return 0;
> > >   }
> > > +static int memblock_add_many_check(void)
> > > +{
> > > +	void *base[INIT_MEMBLOCK_REGIONS + 1];
> > > +	void *orig_region;
> > > +	struct region r = {
> > > +		.base = SZ_16K,
> > > +		.size = MEM_SIZE,
> > > +	};
> > > +
> > > +	PREFIX_PUSH();
> > > +
> > > +	reset_memblock_regions();
> > > +	memblock_allow_resize();
> > > +
> > > +	dummy_physical_memory_many_init(base, INIT_MEMBLOCK_REGIONS);
> > 
> > Why do we need this?
> 
> I want to memblock_add() 128 regions that every region has a valid
> "physical" memory. So it can make sure the memblock_double_array() success
> when add a 129-th region.
> 

> In the last patch, I didn't put this function here, I just memblock_add()
> 128 region at here. And after I think if we can encapsulate it to a
> function, later it can be used to init some valid memory regions into the
> memblock.
> 
> And if no others may be use this functions, the function is not needed.
> 
> > 
> > dummy_physical_memory_init() allocates the "physical" memory, so to trigger
> > memblock_double_array() it's enough to memblock_add() 129 non-intersecting
> > chunks in the range [memory_block.base, memory_block.base + MEM_SIZE].
> > If MEM_SIZE of 16k won't be enough, it can be increased.
> > 
> 
> Yes. And now MEM_SIZE of 16k is enough, no need to increase it now.
> 
I experimented with only calling dummy_physical_memory_init() once at the
beginning and then adding all 129 regions into the memory allocated with
that call. I found that it only works if at least one of the regions is
SZ_16K or larger. I think this is because memblock_double_array() needs to
find a contiguous region large enough to hold
PAGE_ALIGN(new regions array). If all the regions are SZ_8K or smaller, I
get the error message:

memblock: Failed to double memory array from 128 to 256 entries !

What I did was increase MEM_SIZE to SZ_32K, then memblock_add a SZ_16K
region after calling dummy_physical_memory_init() once. Then, I made the
remaining regions SZ_16, with a SZ_16 gap between each region.

> > > +
> > > +	orig_region = memblock.memory.regions;
> > > +
> > > +	/* This adds the 129 memory_region, and makes it double array. */
> > > +	dummy_physical_memory_init();
> > > +	append_memblock();
> > > +	base[INIT_MEMBLOCK_REGIONS] = get_memory_block_base();
> > > +
> > > +	ASSERT_EQ(memblock.memory.cnt, INIT_MEMBLOCK_REGIONS + 1);
> > > +	ASSERT_EQ(memblock.memory.total_size, (INIT_MEMBLOCK_REGIONS + 1) * MEM_SIZE);
> > > +	ASSERT_EQ(memblock.memory.max, INIT_MEMBLOCK_REGIONS * 2);
> > > +
> > > +	/* The base is very small, so it should be insert to the first region. */
> > > +	memblock_add(r.base, r.size);
> > > +	ASSERT_EQ(memblock.memory.regions[0].base, r.base);
> > > +	ASSERT_EQ(memblock.memory.regions[0].size, r.size);
> > > +
> > > +	ASSERT_EQ(memblock.memory.cnt, INIT_MEMBLOCK_REGIONS + 2);
> > > +	ASSERT_EQ(memblock.memory.total_size, (INIT_MEMBLOCK_REGIONS + 2) * MEM_SIZE);
> > > +	ASSERT_EQ(memblock.memory.max, INIT_MEMBLOCK_REGIONS * 2);
> > > +
> > > +	/* Free these allocated memory. */
> > > +	dummy_physical_memory_many_cleanup(base, INIT_MEMBLOCK_REGIONS + 1);
> > > +
> > > +	/*
> > > +	 * The current memory.regions is occupying a range of memory that
> > > +	 * allocated from dummy_physical_memory_init(). After free the memory,
> > > +	 * we must not use it. So restore the origin memory region to make sure
> > > +	 * the tests can run as normal and not affected by the double array.
> > > +	 */
> > > +	memblock.memory.regions = orig_region;
> > > +	memblock.memory.cnt = INIT_MEMBLOCK_REGIONS;
> > > +
> > > +	test_pass_pop();
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >   static int memblock_add_checks(void)
> > >   {
> > >   	prefix_reset();
> > > @@ -339,6 +392,7 @@ static int memblock_add_checks(void)
> > >   	memblock_add_overlap_bottom_check();
> > >   	memblock_add_within_check();
> > >   	memblock_add_twice_check();
> > > +	memblock_add_many_check();
> > >   	prefix_pop();
> > > diff --git a/tools/testing/memblock/tests/common.c b/tools/testing/memblock/tests/common.c
> > > index e43b2676af81..960b3ce07696 100644
> > > --- a/tools/testing/memblock/tests/common.c
> > > +++ b/tools/testing/memblock/tests/common.c
> > > @@ -5,8 +5,6 @@
> > >   #include <linux/memory_hotplug.h>
> > >   #include <linux/build_bug.h>
> > > -#define INIT_MEMBLOCK_REGIONS			128
> > > -#define INIT_MEMBLOCK_RESERVED_REGIONS		INIT_MEMBLOCK_REGIONS
> > >   #define PREFIXES_MAX				15
> > >   #define DELIM					": "
> > > @@ -58,10 +56,20 @@ void reset_memblock_attributes(void)
> > >   	memblock.current_limit	= MEMBLOCK_ALLOC_ANYWHERE;
> > >   }
> > > +void *get_memory_block_base(void)
> > > +{
> > > +	return memory_block.base;
> > > +}
> > > +
> > > +void append_memblock(void)
> > > +{
> > > +	memblock_add((phys_addr_t)memory_block.base, MEM_SIZE);
> > > +}
> > > +
> > >   void setup_memblock(void)
> > >   {
> > >   	reset_memblock_regions();
> > > -	memblock_add((phys_addr_t)memory_block.base, MEM_SIZE);
> > > +	append_memblock();
> > >   }
> > >   void dummy_physical_memory_init(void)
> > > @@ -75,6 +83,30 @@ void dummy_physical_memory_cleanup(void)
> > >   	free(memory_block.base);
> > >   }
> > > +void dummy_physical_memory_many_init(void *base[], int cnt)
> > > +{
> > > +	int i;
> > > +
> > > +	for (i = 0; i < cnt; i++) {
> > > +		dummy_physical_memory_init();
> > > +		append_memblock();
> > > +		base[i] = memory_block.base;
> > > +
> > > +		ASSERT_EQ(memblock.memory.cnt, i + 1);
> > > +		ASSERT_EQ(memblock.memory.total_size, (i + 1) * MEM_SIZE);
> > > +	}
> > > +}
> > > +
> > > +void dummy_physical_memory_many_cleanup(void *base[], int cnt)
> > > +{
> > > +	int i;
> > > +
> > > +	for (i = 0; i < cnt; i++) {
> > > +		memory_block.base = base[i];
> > > +		dummy_physical_memory_cleanup();
> > > +	}
> > > +}
> > > +
> > >   static void usage(const char *prog)
> > >   {
> > >   	BUILD_BUG_ON(ARRAY_SIZE(help_opts) != ARRAY_SIZE(long_opts) - 1);
> > > diff --git a/tools/testing/memblock/tests/common.h b/tools/testing/memblock/tests/common.h
> > > index 3e7f23d341d7..848900aa8db6 100644
> > > --- a/tools/testing/memblock/tests/common.h
> > > +++ b/tools/testing/memblock/tests/common.h
> > > @@ -11,6 +11,8 @@
> > >   #include <../selftests/kselftest.h>
> > >   #define MEM_SIZE SZ_16K
> > > +#define INIT_MEMBLOCK_REGIONS			128
> > > +#define INIT_MEMBLOCK_RESERVED_REGIONS		INIT_MEMBLOCK_REGIONS
> > >   /**
> > >    * ASSERT_EQ():
> > > @@ -68,8 +70,12 @@ struct region {
> > >   void reset_memblock_regions(void);
> > >   void reset_memblock_attributes(void);
> > >   void setup_memblock(void);
> > > +void append_memblock(void);
> > > +void *get_memory_block_base(void);
> > >   void dummy_physical_memory_init(void);
> > >   void dummy_physical_memory_cleanup(void);
> > > +void dummy_physical_memory_many_init(void *base[], int cnt);
> > > +void dummy_physical_memory_many_cleanup(void *base[], int cnt);
> > >   void parse_args(int argc, char **argv);
> > >   void test_fail(void);
> > > -- 
> > > 2.30.2
> > > 
> > > 
> > 
Thanks,
Rebecca