muvarov replied on github web page:
platform/linux-generic/_ishm.c
line 23
@@ -1436,15 +1436,23 @@ int _odp_ishm_cleanup_files(const char *dirpath)
return 0;
}
-int _odp_ishm_init_global(void)
+int _odp_ishm_init_global(const odp_init_t *init)
{
void *addr;
void *spce_addr;
int i;
uid_t uid;
char *hp_dir = odp_global_data.hugepage_info.default_huge_page_dir;
uint64_t align;
+ uint64_t max_memory = ODP_CONFIG_ISHM_VA_PREALLOC_SZ;
+ uint64_t internal = ODP_CONFIG_ISHM_VA_PREALLOC_SZ / 8;
Comment:
'internal' has to be also adjusted. Or you can get overflow at line 1455.
> Petri Savolainen(psavol) wrote:
> If max size is 4GB, max align is 1GB. A resevation may consume e.g. 4.5GB
> memory. Again it depends on other applications and ODP instances if such
> amount of system memory is still free when application tries to reserve it.
> Maybe first couple instances succeeded, but then system did run out of memory.
>> Petri Savolainen(psavol) wrote:
>> In the example, system is 64 bit, has e.g. 32 GB of memory, ODP SHM
>> implementation is limited e.g. by address space pre-reservation etc (e.g. 32
>> bits / 4GB). So, ODP implementation limits max SHM size to 4GB, 0 cannot be
>> used as capability. A 4 GB reservation succeeds as long as system has memory
>> free. When other applications or ODP instances have reserved all 32GB
>> memory, yet another 4GB reservation will fail.
>>
>> So, 0 says that there's no other limit than amount of currently free memory.
>> E.g. odp-linux implementation lied by returning 0 and at the same time
>> limiting max reservation to 512MB (due to fixed size address space
>> allocation).
>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>> Again, what does the application gain from having a non-zero `max_align`
>>> returned if it's unable to make use of it?
>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>> The 0 value is intended to say that addressability / available memory is
>>>> the only limit, so again in this case the implementation should return 0,
>>>> not 4GB. If the implementation says 0 and the application tries to reserve
>>>> something huge and that fails that's OK. The application needs to check
>>>> RCs in any event. But what's the point of having a non-zero limit if
>>>> there's no reasonable expectation that it means anything? At that point
>>>> it's useless and might as well be ignored.
>>>>> Petri Savolainen(psavol) wrote:
>>>>> 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_r166369542
updated_at 2018-02-06 16:53:19
