> From: Seth Jennings [mailto:sjenning@xxxxxxxxxxxxxxxxxx] > Subject: Re: [PATCH v2 0/3] staging: zcache: xcfmalloc support > > Hey Nitin, > > So this is how I see things... > > Right now xvmalloc is broken for zcache's application because > of its huge fragmentation for half the valid allocation sizes > (> PAGE_SIZE/2). Um, I have to disagree here. It is broken for zcache for SOME set of workloads/data, where the AVERAGE compression is poor (> PAGE_SIZE/2). > My xcfmalloc patches are _a_ solution that is ready now. Sure, > it doesn't so compaction yet, and it has some metadata overhead. > So it's not "ideal" (if there is such I thing). But it does fix > the brokenness of xvmalloc for zcache's application. But at what cost? As Dave Hansen pointed out, we still do not have a comprehensive worst-case performance analysis for xcfmalloc. Without that (and without an analysis over a very large set of workloads), it is difficult to characterize one as "better" than the other. > So I see two ways going forward: > > 1) We review and integrate xcfmalloc now. Then, when you are > done with your allocator, we can run them side by side and see > which is better by numbers. If yours is better, you'll get no > argument from me and we can replace xcfmalloc with yours. > > 2) We can agree on a date (sooner rather than later) by which your > allocator will be completed. At that time we can compare them and > integrate the best one by the numbers. > > Which would you like to do? Seth, I am still not clear why it is not possible to support either allocation algorithm, selectable at runtime. Or even dynamically... use xvmalloc to store well-compressible pages and xcfmalloc for poorly-compressible pages. I understand it might require some additional coding, perhaps even an ugly hack or two, but it seems possible. 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href