Messages in this thread | | | Date | Thu, 23 Dec 2004 13:02:57 -0800 (PST) | From | Christoph Lameter <> | Subject | Re: Prezeroing V2 [0/3]: Why and When it works |
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On Thu, 23 Dec 2004, Andi Kleen wrote:
> > 1. Aggregating zeroing operations to only apply to pages of higher order, > > which results in many pages that will later become order 0 to be > > zeroed in one go. For that purpose the existing clear_page function is > > extended and made to take an additional argument specifying the order of > > the page to be cleared. > > But if you do that you should really use a separate function that > can use cache bypassing stores. > > Normal clear_page cannot use that because it would be a loss > when the data is soon used.
Clear_page is used both in the cache hot and no cache wanted case now.
> So the two changes don't really make sense.
Which two changes?
If an arch can do zeroing without touching the cpu caches then that can be done with a zero driver.
> Also I must say I'm still suspicious regarding your heuristic > to trigger gang faulting - with bad luck it could lead to a lot > more memory usage to specific applications that do very sparse > usage of memory.
Gang faulting is not part of this patch. Please keep the issues separate.
> There should be at least an madvise flag to turn it off and a sysctl > and it would be better to trigger only on a longer sequence of > consecutive faulted pages.
Again this is not related to this patchset. Look at the V13 of the page fault scalability patch and you will find a /proc/sys/vm setting to manipulate things. This is V2 of the prezeroing patch.
> How about some numbers on i386?
Umm. Yeah. I only have smallish i386 machines here. Maybe next year ;-) - 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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