Petri Savolainen(psavol) replied on github web page:
test/validation/api/shmem/shmem.c
@@ -212,6 +214,55 @@ void shmem_test_basic(void)
CU_ASSERT(0 == odp_shm_free(shm));
}
+/*
+ * maximum size reservation
+ */
+static void shmem_test_max_reserve(void)
+{
+ odp_shm_capability_t capa;
+ odp_shm_t shm;
+ uint64_t size, align;
+ uint8_t *data;
+ uint64_t i;
+
+ memset(&capa, 0, sizeof(odp_shm_capability_t));
+ CU_ASSERT_FATAL(odp_shm_capability(&capa) == 0);
+
+ CU_ASSERT(capa.max_blocks > 0);
+
+ size = capa.max_size;
+ align = capa.max_align;
+
+ /* Assuming that system has at least MAX_MEMORY_USED bytes available */
+ if (capa.max_size == 0 || capa.max_size > MAX_MEMORY_USED)
+ size = MAX_MEMORY_USED;
+
+ if (capa.max_align == 0 || capa.max_align > MEGA)
+ align = MEGA;
Comment:
Maybe with 1GB hugepages the max align is 1GB, and 16GB hugepages 16GB, ...
> Petri Savolainen(psavol) wrote:
> Implementation may have a limitation of e.g. 4GB due to limit of using a 32
> bit address space reservation, etc. It would be waste to reserve 4GB of
> system memory for every ODP instance, as implementation could not guarantee
> 4GB otherwise, as other applications allocate memory as well. So, init phase
> there could be 4.2GB available, but by the time ODP application starts
> calling shm_reserve() there would be less than 4GB left and some reserves
> would fail.
>
> So, implementation may have large upper limit, which is not related to amount
> of available memory but e.g. due implementation of the address mapping
> (number of bits, hugepages, etc).
>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>> Same story as for `capa.max_size`. I'd expect most implementations to return
>> `capa.max_align` to be either 0 or some reasonable value like 4K or 1M.
>> However, if they specify something else then they should be able to deliver
>> that.
>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>> If the implementation doesn't have a specific predefined upper limit then
>>> it should return `capa.max_size == 0`. If it says it has a non-zero upper
>>> limit then if it's unable to provide that limit that's a failure. Otherwise
>>> what's the point of having a specified limit?
>>>> Petri Savolainen(psavol) wrote:
>>>> I'll add comment about zero value. Although, I already changed
>>>> documentation to require param_init() call and say that don't change
>>>> values that you are not going to use (init sets it to zero).
>>>>> Petri Savolainen(psavol) wrote:
>>>>> OK
>>>>>> Petri Savolainen(psavol) wrote:
>>>>>> Very large align could result very large allocation and thus again
>>>>>> system run out of memory (e.g. 1TB align => >1TB alloc).
>>>>>>
>>>>>> OK. I'll change align max to be a power of two.
>>>>>>> Petri Savolainen(psavol) wrote:
>>>>>>> Since actual amount of available memory typically depends on system
>>>>>>> load. SHM implementation may not have a limit (max_size==0), or limit
>>>>>>> may be due to address space (e.g. 40bit == 1TB). System might not have
>>>>>>> always the max amount (e.g. 1TB) available. I limit validation test to
>>>>>>> assume that at least 100MB should be always available.
>>>>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>>>>> @muvarov `odp_shm_capability()` already tells the application the
>>>>>>>> largest contiguous size it can reserve (`max_size`) and the maximum
>>>>>>>> number of reserves it can do (`max_blocks`). This is just hinting to
>>>>>>>> the implementation the total size of all reserves the application will
>>>>>>>> do.
>>>>>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>>>>>> An additional `printf()` giving a bit more detail (i.e., `i` value)
>>>>>>>>> would be useful here.
>>>>>>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>>>>>>> Shouldn't `MEGA` be a power of 2 for alignment purposes? I.e., 1024
>>>>>>>>>> x 1024 rather than 1000 x 1000? And if the implementation supports
>>>>>>>>>> an even higher `max_align` why not test that as well?
>>>>>>>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>>>>>>>> Why do you want to limit the size in a test that named
>>>>>>>>>>> `shmem_test_max_reserve()`? If `capa.max_size == 0` then you have
>>>>>>>>>>> to pick a specific target, but if it's non-zero why wouldn't you
>>>>>>>>>>> want to try to reserve that much to see if the limit is true?
>>>>>>>>>>>> muvarov wrote
>>>>>>>>>>>> 0 - means not specified. And what about continuous of memory
>>>>>>>>>>>> chunks? Requesting one big continues shared memory chunk is not
>>>>>>>>>>>> general solution.
https://github.com/Linaro/odp/pull/446#discussion_r165648771
updated_at 2018-02-02 13:50:47
