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Date: Sat, 11 Nov 2006 00:13:24 -0500 From: Mathieu Desnoyers <compudj@...stal.dyndns.org> To: Ralf Baechle <ralf@...ux-mips.org> Cc: linux-kernel@...r.kernel.org, ltt-dev@...fik.org Subject: Re: MIPS atomic operations, "sync" * Ralf Baechle (ralf@...ux-mips.org) wrote: > On Fri, Nov 10, 2006 at 01:40:49PM -0500, Mathieu Desnoyers wrote: > > > I am currently creating a "LOCK" prefix free and memory barrier free version > > of atomic.h to fulfill my tracer (LTTng) needs, which is to atomically update > > per-cpu data and have a minimal performance loss. > > > > I just came across the MIPS atomic.h and system.h implementations in 2.6.18 > > which brings a question : > > > > Why are the primitives in include/asm-mips/atomic.h using the "sync" > > instruction even in the UP case ? system.h cmpxchg only uses the sync in the > > SMP case. > > Why are the standard atomic operations insufficient for your needs? > > There is an enormous amout of subtilities in those atomic ops for some > architectures you probably do yourself a big favor by avoiding new > variants. > Performance cost. I add a memory barrier where needed when the data needs to appear to be written sequentially from the other CPUs perspective. Mathieu OpenPGP public key: http://krystal.dyndns.org:8080/key/compudj.gpg Key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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