Re: [Xen-devel] [PATCH RESEND RFC 0/8] Memory scrubbing from idle loop

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 27/02/17 17:06, Boris Ostrovsky wrote:
>>> Briefly, the new algorithm places dirty pages at the end of heap's page list
>>> for each node/zone/order to avoid having to scan full list while searching
>>> for dirty pages. One processor form each node checks whether the node has 
>>> any
>>> dirty pages and, if such pages are found, scrubs them. Scrubbing itself
>>> happens without holding heap lock so other users may access heap in the
>>> meantime. If while idle loop is scrubbing a particular chunk of pages this
>>> chunk is requested by the heap allocator, scrubbing is immediately stopped.
>> Why not maintain two lists?  That way it is O(1) to find either a clean
>> or dirty free page.
> 
> Since dirty pages are always at the tail of page lists we are not really
> searching the lists. As soon as a clean page is found (starting from the
> tail) we can stop.

Sure, having a back and a front won't add significant overhead; but it
does make things a bit strange.  What does it buy us over having two lists?

 -George


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel