Re: [Xen-devel] is paging_new_log_dirty_page alloc page harmfull?

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 11:11 +0000 on 04 Mar (1299237101), MaoXiaoyun wrote:
> Hi:
> 
>       I've been testing on memory overcommit on Xen by using balloon driver.
> On our stress test, it is possilbe that heap memory in xen is use up. Thus 
> the serial
> port will show log as below:
> 
> (XEN) paging_log_dirty_range: 138 failed page allocs while logging dirty pages
> (XEN) paging_log_dirty_range: 138 failed page allocs while logging dirty pages
> (XEN) paging_log_dirty_range: 138 failed page allocs while logging dirty pages
> 
> I am asking is it harmfull to domain?

It means that the log-dirty code wasn't able to extend its bitmap and
callers have to assume that all pages are dirty.  It's bad for
performance but should be OK.

If you rebase to the latest 4.1 RC, this particular message should go
away as log-dirty bitmaps are no longer pulled from common memory.

> If so, I might need find a way to reserve some memory for xen, which looks
> kinds of difficult.

I think you might find you need to do this anyway - there are other
dynamic allocations in Xen which might not fail so gracefully (in
particular around setting up new domains).

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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