Re: How much do the hint bits help?

On Tue, Dec 21, 2010 at 7:20 PM, Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:
> On Tue, Dec 21, 2010 at 7:06 PM, Mark Kirkwood
> <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz> wrote:
>> On 22/12/10 13:05, Mark Kirkwood wrote:
>>>
>>> On 22/12/10 11:42, Merlin Moncure wrote:
>>>>
>>>> Attached is an incomplete patch disabling hint bits based on compile
>>>> switch.  It's not complete, for example it's not reconciling some
>>>> assumptions in heapam.c that hint bits have been set in various
>>>> routines.  However, it mostly passes regression and I deemed it good
>>>> enough to run some preliminary benchmarks and fool around.  Obviously,
>>>> hint bits are an annoying impediment to a couple of other cool pending
>>>> features, and it certainly would be nice to operate without them.
>>>> Also, for particular workloads, the extra i/o hint bits can cause a
>>>> fair amount of pain.
>>>
>>> Looks like a great idea to test, however I don't seem to be able to
>>> compile with it applied: (set#define DISABLE_HINT_BITS 1 at the end of
>>> src/include/pg_config_manual.h)
>>>
>>> gcc -O2 -Wall -Wmissing-prototypes -Wpointer-arith
>>> -Wdeclaration-after-statement -Wendif-labels -fno-strict-aliasing -fwrapv -g
>>> -I../../../../src/include -D_GNU_SOURCE -c -o heapam.o heapam.c
>>> heapam.c: In function ‘HeapTupleHeaderAdvanceLatestRemovedXid’:
>>> heapam.c:3867: error: ‘HEAP_XMIN_COMMITTED’ undeclared (first use in this
>>> function)
>>> heapam.c:3867: error: (Each undeclared identifier is reported only once
>>> heapam.c:3867: error: for each function it appears in.)
>>> heapam.c:3869: error: ‘HEAP_XMIN_INVALID’ undeclared (first use in this
>>> function)
>>> make[4]: *** [heapam.o] Error 1
>>>
>>
>> Arrg, sorry - against git head on Ubuntu 10.03 (gcc 4.4.3)
>
> did you check to see if the patch applied clean? btw I was working
> against postgresql-9.0.1...

ah, this is the problem (9.0.1 vs head). to work vs head it prob
needs a few more tweaks. you can also try removing it yourself --
most of the changes follow a similar pattern.

merlin