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Rusty Russell a écrit : > On Friday 16 May 2008 23:41:16 Mike Travis wrote: > >> Eric Dumazet wrote: >> >>> Rusty Russell a écrit : >>> >>>> Any chance I can ask you look at the issue of full dynamic per-cpu >>>> allocation? >>>> >>> You mean using alloc_percpu() ? Problem is that current implementation >>> is expensive, >>> > > I mean rewriting alloc_percpu :) > > >>> We probably can change this to dynamic per-cpu as soon as Mike or >>> Christopher finish their work on new dynamic per-cpu implementation ? >>> >> Yes, the zero-based percpu variables followed by the cpu_alloc patch should >> provide this and shrink the code quite well, including in some cases >> removing locking requirements (because the resultant instructions will be >> atomic.) >> > > Ah, I hadn't realized that Mike was already working on this. Mike, have you > published patches already? > > Christoph Lameter made good work last year and apparently the path is to : 1) Put pda at the begining of percpu section. 2) Relocate percpu variables to begin at zero 3) Use %gs (or %fs) register to address pda AND percpu section. 4) Reserve an appropriate large virtual zone into percpu section so that it can fullfill : - percpu "static" allocations needed by module loader. - per_cpu "dynamic" allocations (No more need for an array of pointers to find the address of dynamic per_cpu variable) - Eventually allocates PAGES dynamically into this zone to satisfy any size of percpu needs. (But with a limit of say 256 MB per cpu on x86_64) Thats a lot of work and apparently Mike and Christoph are doing it. Some pointers to previous work: http://groups.google.pl/group/linux.kernel/browse_thread/thread/f2ff6901ca6ae9fc/b2ed3b7f3612a157?lnk=raot http://kerneltrap.org/mailarchive/linux-kernel/2008/2/1/683104 http://linux.derkeiler.com/Mailing-Lists/Kernel/2008-01/msg09052.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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