On Wed, 2013-02-06 at 10:40 -0800, Dan Magenheimer wrote: > > From: Simon Jeons [mailto:simon.jeons@xxxxxxxxx] > > Subject: Re: [LSF/MM TOPIC] In-kernel compression in the MM subsystem > > > > Hi Dan, > > On Sat, 2013-01-26 at 12:16 -0800, Dan Magenheimer wrote: > > > There's lots of interesting things going on in kernel memory > > > management, but one only(?) increases the effective amount > > > of data that can be stored in a fixed amount of RAM: in-kernel > > > compression. > > > > > > Since ramzswap/compcache (now zram) was first proposed in 2009 > > > as an in-memory compressed swap device, there have been a number > > > of in-kernel compression solutions proposed, including > > > zcache, kztmem, and now zswap. Each shows promise to improve > > > performance by using compression under memory pressure to > > > reduce I/O due to swapping and/or paging. Each is still > > > in staging (though zram may be promoted by LSFMM 2013) > > > because each also brings a number of perplexing challenges. > > > > > > I think it's time to start converging on which one or more > > > of these solutions, if any, should be properly promoted and > > > more fully integrated into the kernel memory management > > > subsystem. Before this can occur, it's important to build a > > > broader understanding and, hopefully, also a broader consensus > > > among the MM community on a number of key challenges and questions > > > in order to guide and drive further development and merging. > > > > > > I would like to collect a list of issues/questions, and > > > start a discussion at LSF/MM by presenting this list, select > > > the most important, then lead a discussion on how ever many > > > there is time for. Most likely this is an MM-only discussion > > > though a subset might be suitable for a cross-talk presentataion. > > > > > > > Is there benchmark to test each component in tmem? > > Hi Simon -- > > I'm not sure what you mean. Could you add a few words > to clarify? > Hi Dan, Some questions about zsmalloc: 1) What's the meaning of comment above USE_PGTABLE_MAPPING macro "This cause zsmalloc to use page table mapping rather than copying for object mapping"? 2) How zsmalloc handle object span two pages? It seems that in function init_zspage, link->next = obj_location_to_handle(next_page, 0); you encode next_page and 0 to object, then how can zs_malloc find this free object? IIUC, this encode skip the object span two pages. 3) Why must map after malloc if want to use a object? 4) What's the number of ZS_MAX_ALLOC_SIZE and ZS_MIN_ALLOC_SIZE? There are too many macros to figure it out. Thanks, Simon > Thanks, > Dan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>