On Sat, Sep 13, 2014 at 06:35:34PM +0400, Konstantin Khlebnikov wrote: > This patch implements user-space per-cpu memory in the same manner as in > kernel-space: each cpu has its own %gs base address. On x86_64 %fs is used > for thread local storage, %gs usually is free. > > User-space application cannot prevent preemption but x86 read-modify-write > operations are atomic against interrupts and context switches. Thus percpu > counters, ring-buffer cursors, per-cpu locks and other cool things might > be implemented in a very efficient way.
Do you have some concrete examples for the more complex operations? It seems to me the limitation to a simple instruction will be very limiting for anything more complicated than a counter. Also it's not even clear how someone would implement retry (short of something like kuchannel) Of course it wouldn't be a problem with TSX transactions, but it's not clear they need it. The other problem with the approach is, how would cpu hotplug be handled? > By the way, newer Intel cpus have even faster instructions for > changing %fs/%gs, but they are still not supported by the kernel. Patch kits are pending. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
