Re: [RFC][PATCH 1/3] tracking dirty pages in shared mappings -V4

[Nick Piggin <nickpiggin@yahoo.com.au>]

Linus Torvalds wrote:
> On Tue, 9 May 2006, Martin Bligh wrote:
> 
>>Peter Chubb wrote:
>>
>>>What does this do to performance on TPC workloads?  How many extra
>>>faults are there likely to be?
>>
>>They all use large pages anyway ...
> 
> 
> Yes, but we should really answer that question anyway.
> 
> I don't think anybody has really objected to this patch series, and it 
> clearly seems to fix something (if nothing else, then Peter's test-program 
> ;), and for fairly obvious reasons _I_ approve of it.
> 
> But I've been asking people to benchmark it anyway. Becuase it _will_ hurt 
> users of shared writable mappings, even if it's hopefully less of an issue 
> today thanks to large pages. 
> 
> Now, the fact that it will hurt them is not a total disaster, since we 
> already know that there are ways to mitigate it. However, it's still true 
> that we should have the numbers, if only to perhaps be able to say that we 
> don't care.

Those filesystems (shmem, presumably hugetlbfs) that are
!mapping_cap_account_dirty should not notice any difference, except
perhaps for the several extra branches and bytes of icahce.

Or do these databases use regular filesystem backed shared files?

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