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SubjectRe: [PATCH] mm: use-once cleanup
Martin J. Bligh wrote:
>
>>> Peter Zijlstra wrote:
>>>
>>>> Hi,
>>>>
>>>> This is yet another implementation of the PG_useonce cleanup spoken of
>>>> during the VM summit.
>>>>
>>> After getting bitten by rsync yet again, I guess it's time to insist
>>> that this patch gets merged...
>>>
>>> Andrew, could you merge this? Pretty please? ;)
>>>
>>>
>>
>> Guys, this is a performance patch, right?
>>
>> One which has no published performance testing results, right?
>>
>> It would be somewhat odd to merge it under these circumstances.
>>
>> And this applies to all of these
>> hey-this-is-cool-but-i-didnt-bother-testing-it MM patches which people
>> are
>> throwing around. This stuff is *hard*. It has a bad tendency to cause
>> nasty problems which only become known months after the code is merged.
>>
>> I shouldn't have to describe all this, but
>>
>> - Identify the workloads which it's supposed to improve, set up tests,
>> run tests, publish results.
>>
>> - Identify the workloads which it's expected to damage, set up tests, run
>> tests, publish results.
>>
>> - Identify workloads which aren't expected to be impacted, make a good
>> effort at demonstrating that they are not impacted.
>>
>> - Perform stability/stress testing, publish results.
>>
>> Writing the code is about 5% of the effort for this sort of thing.
>>
>> Yes, we can toss it in the tree and see what happens. But it tends to be
>> the case that unless someone does targetted testing such as the above,
>> regressions simply aren't noticed for long periods of time. <wonders
>> which
>> schmuck gets to do the legwork when people report problems>
>>
>> Just the (unchangelogged) changes to the
>> when-to-call-mark_page_accessed()
>> logic are a big deal. Probably these should be a separate patch -
>> separately changelogged, separately tested, separately justified.
>>
>> Performance testing is *everything* for this sort of patch and afaict
>> none
>> has been done, so it's as if it hadn't been written, no?
>> -
>>
>>
>>
> Rik / Peter ... I lost the original mail + patch, but if you put it
> up on a URL somewhere, Andy would probably run it through the test
> harness for at least some basic perf testing, if you ask him ;-)
> Probably against mainline, not -mm, as -mm seems to have other
> problems right now.

I'll happily run it through the test suites once I get my machines
working again after 2.6.18-rc2-mm1 has finished with them :(.

-apw
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