[Rd] Help to create bugzilla account

[Simon Urbanek]

> On Aug 11, 2017, at 12:57 PM, Iñaki Úcar <i.ucar86 at gmail.com> wrote:
> 
> 2017-08-11 16:00 GMT+02:00 Martin Maechler <maechler at stat.math.ethz.ch>:
>>>>>>> Dmitriy Selivanov <selivanov.dmitriy at gmail.com>
>>>>>>>    on Fri, 11 Aug 2017 17:33:31 +0400 writes:
>> 
>>> Hi mailing list and R-core. Could someone from R-core please help me to
>>> create account in bugzilla? I would like to submit issue related to gc() to
>>> wishlist.
>> 
>> I will create one.
>> 
>> Your previous e-mails left me pretty clueless about what the
>> problem is that you want to solve ... but maybe others
>> understand better what you mean.
>> 
>> Note that in the case of such a relatively sophisticated wish
>> without a clear sign of a problem (in my view)
>> chances are not high that anything will change, unless someone
>> provides a (small footprint) patch towards the (R-devel aka
>> "trunk") sources *and* reproducible R code that depicts the
>> problem.
> 
> How to reproduce it:
> 
> a <- replicate(2e6, new.env()) # ~ 1.4 GB of memory
> rm(a)
> gc() # the R process still has the memory assigned
> 

Right, but that's unavoidable because of the way Linux allocates memory - see FAQ 7.42
The memory is free, Linux just keeps it for future allocations.

Running malloc.trim doesn't help, because the issue is fragmentation due to the linear design of the pool - you likely will have another object on top so in most practical cases malloc.trim() doesn't actually do anything. You can always call malloc.trim() yourself is you think it helps, but it doesn't in the general case. The only way to address that would be to move allocated objects from top of the pool down, but that's not something R can allow, because it cannot know which code still has SEXP pointers referring to that object.

Cheers,
Simon