Re: [PATCH 0/9] mem: reduce memory fragmentation

[Thomas Monjalon <thomas@monjalon.net>]

11/06/2018 22:55, Anatoly Burakov:
> This patchset is mostly dealing with changes fbarray, but it is
> actually about reducing fragmentation in Linuxapp memalloc.
> 
> We allocate hugepages from lower VA to higher VA. However, our
> malloc heap allocates addresses from higher VA to lower VA. This
> results in a situation where, whenever new page is allocated,
> malloc starts to allocate memory from the top, leaving fragmented
> space between new allocation's leftover and previous leftover.
> 
> Over time, this leads to lots of free elements sitting at page
> boundaries, small enough to be useful but large enough to have an
> impact on memory fragmentation in certain circumstances.
> 
> To fix this, we need to allocate memory from higher VA first.
> However, in order to do that, we need the ability to search fbarray
> in reverse, which is currently not supported. Adding this support is
> what most of this patchset is about.
> 
> First 4 patches fix some issues in existing fbarray implementation
> and remove some code duplication, preparing for adding of new
> functionality.
> 
> Next 3 patches add new functionality - reverse search of used/free
> slots, mirroring already existing functionality in semantics and
> capable of returning identical results but in reverse order.
> 
> Patch 8 adds unit tests for fbarray, testing both existing and new
> functionality.
> 
> Finally, patch 9 changes memalloc to look up free slots in memseg
> list in reverse order. No other changes is necessary, as all other
> code can handle segments, wherever they are allocated.
> 
> Anatoly Burakov (9):
>   fbarray: fix errno values returned from functions
>   fbarray: reduce duplication in find_contig code
>   fbarray: reduce duplication in find_next_n code
>   fbarray: reduce duplication in find_next code
>   fbarray: add reverse find_free/used
>   fbarray: add reverse find n used/free
>   fbarray: add reverse find contig used/free
>   test: add fbarray autotests
>   memalloc: allocate memory in reverse

Applied, thanks