[SLOF] [PATCH] Improve SLOF_alloc_mem_aligned()

[Alexey Kardashevskiy]

On 14/09/16 15:39, Alexey Kardashevskiy wrote:
> On 05/09/16 19:28, Thomas Huth wrote:
>> When loading a file via the spapr-vlan network interface, SLOF
>> currently leaks quite a lot of memory, about 12kB each time.
>> This happens mainly because veth_init() uses for example
>> SLOF_alloc_mem_aligned(8192, 4096) and similar calls to get
>> the memory, but the space for the additional alignment is never
>> returned anymore later. An easy way to ease this situation is to
>> improve SLOF_alloc_mem_aligned() a little bit. We normally get memory
>> from SLOF_alloc_mem() which is aligned pretty well already, thanks to
>> the buddy allocator in SLOF. So we can try to first get a memory
>> block with the exact size first, and only do the alignment dance
>> if the first allocation was not aligned yet.
>>
>> Signed-off-by: Thomas Huth <thuth at redhat.com>
> 
> I do not like it but since the allocated address does not store the size
> somewhere nearby, I'll apply this anyway, thanks.

I asked for advice and we could actually always try allocating
(size+align-1) here, and then if the address is not aligned - free the
chunk before aligned address, if aligned - free the chunk after addr+size.



> 
> 
>> ---
>>  slof/helpers.c | 11 ++++++++---
>>  1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/slof/helpers.c b/slof/helpers.c
>> index 48c34a6..b049141 100644
>> --- a/slof/helpers.c
>> +++ b/slof/helpers.c
>> @@ -69,9 +69,14 @@ void *SLOF_alloc_mem(long size)
>>  
>>  void *SLOF_alloc_mem_aligned(long size, long align)
>>  {
>> -	unsigned long addr = (unsigned long)SLOF_alloc_mem(size + align - 1);
>> -	addr = addr + align - 1;
>> -	addr = addr & ~(align - 1);
>> +	unsigned long addr = (unsigned long)SLOF_alloc_mem(size);
>> +
>> +	if (addr % align) {
>> +		SLOF_free_mem((void *)addr, size);
>> +		addr = (unsigned long)SLOF_alloc_mem(size + align - 1);
>> +		addr = addr + align - 1;
>> +		addr = addr & ~(align - 1);
>> +	}
>>  
>>  	return (void *)addr;
>>  }
>>
> 
> 


-- 
Alexey