Messages in this thread | | | Date | Tue, 25 Mar 2008 00:40:31 +0530 | From | "Nitin Gupta" <> | Subject | Re: [PATCH 3/6] compcache: TLSF Allocator interface |
| |
On Tue, Mar 25, 2008 at 12:26 AM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > > On Mon, 2008-03-24 at 23:04 +0530, Nitin Gupta wrote: > > On Mon, Mar 24, 2008 at 10:26 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > > > On Mon, 2008-03-24 at 20:34 +0530, Nitin Gupta wrote: > > > > Two Level Segregate Fit (TLSF) Allocator is used to allocate memory for > > > > variable size compressed pages. Its fast and gives low fragmentation. > > > > Following links give details on this allocator: > > > > - http://rtportal.upv.es/rtmalloc/files/tlsf_paper_spe_2007.pdf > > > > - http://code.google.com/p/compcache/wiki/TLSFAllocator > > > > > > > > This kernel port of TLSF (v2.3.2) introduces several changes but underlying > > > > algorithm remains the same. > > > > > > > > Changelog TLSF v2.3.2 vs this kernel port > > > > - Pool now dynamically expands/shrinks. > > > > It is collection of contiguous memory regions. > > > > - Changes to pool create interface as a result of above change. > > > > - Collect and export stats (/proc/tlsfinfo) > > > > - Cleanups: kernel coding style, added comments, macros -> static inline, etc. > > > > > > Can you explain why you need this allocator, why don't the current > > > kernel allocators work for you? > > > > > > > > > > kmalloc() allocates one of pre-defined sizes (as defined in > > kmalloc_sizes.h). This will surely cause severe fragmentation with > > these variable sized compressed pages. > > > > Whereas, TLSF maintains very fine grained size lists. In all the > > workloads I tested, it showed <5% fragmentation. Also, its very simple > > as just ~700 LOC. > > Yeah, it also suffers from a horrible coding style, can use excessive > amounts of vmalloc space, isn't hooked into the reclaim process as an > allocator should be and has a severe lack of per-cpu data making it a > pretty big bottleneck on anything with more than a few cores. > > Now, it might be needed, might work better, and the scalability issue > might not be a problem when used for swap, but still, you don't treat > any of these points in your changelog.
Currently, this TLSF implementation is not scalable at all (and thats why it depends on EMBEDDED).
> > FWIW, please split up the patches in a sane way. This series looks like > it wants to be 2 or 3 patches. The first introducing all of TLSF (this > split per file is horrible). The second doing all of the block device, > and a possible last doing documentation and such. > > Also, how bad was kmalloc() compared to this TLSF, we need numbers :-) > >
Ok, I will get them and present here.
Thanks, Nitin
| |