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Date: Fri, 24 Jul 2009 12:21:50 +0200 From: Thomas Hellstrom <thellstrom@...are.com> To: Andi Kleen <andi@...stfloor.org> CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "mingo@...e.hu" <mingo@...e.hu>, "venkatesh.pallipadi@...el.com" <venkatesh.pallipadi@...el.com> Subject: Re: [PATCH] x86: Use clflush() instead of wbinvd() whenever possible when changing mapping Andi Kleen wrote: > Thomas Hellstrom <thellstrom@...are.com> writes: > > >> The current code uses wbinvd() when the area to flush is > 4MB. Although this >> may be faster than using clflush() the effect of wbinvd() on irq latencies >> may be catastrophical on systems with large caches. Therefore use clflush() >> > > may be? You seem to miss some hard data here. > > Admittedly. However, the concept of flushing and invalidating the caches completely on systems with many processors and huge caches when we intend to only flush only small piece of the cache also sounds like a big overkill. Furthermore, since the wbinvd() has been introduced as an optimization of the general clflush() case, did somebody ever check the effects on systems with many processors and huge caches? /Thomas > -Andi > > -- 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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