On Thu, Jun 23, 2022 at 2:09 AM Robert Haas wrote:
> On Wed, Jun 22, 2022 at 12:34 AM Thomas Munro wrote:
> > > For the record, the third idea proposed was to use 1 for the first
> > > byte, so that 0 is reserved for NULL and works with memset(0). Here's
> > > an attempt at that.
> >
> > ...
On Wed, Jun 22, 2022 at 12:34 AM Thomas Munro wrote:
> > For the record, the third idea proposed was to use 1 for the first
> > byte, so that 0 is reserved for NULL and works with memset(0). Here's
> > an attempt at that.
>
> ... erm, though, duh, I forgot to adjust Assert(val > base). One more
On Wed, Jun 22, 2022 at 4:24 PM Thomas Munro wrote:
> On Wed, Jun 22, 2022 at 2:54 PM Tom Lane wrote:
> > John Naylor writes:
> > > On Wed, Jun 1, 2022 at 2:57 AM Robert Haas wrote:
> > >> ... So we can fix this by:
> > >> 1. Using a relative pointer value other than 0 to represent a null
> >
On Wed, Jun 22, 2022 at 2:54 PM Tom Lane wrote:
> John Naylor writes:
> > On Wed, Jun 1, 2022 at 2:57 AM Robert Haas wrote:
> >> ... So we can fix this by:
> >> 1. Using a relative pointer value other than 0 to represent a null
> >> pointer. Andres suggested (Size) -1.
> >> 2. Not storing the
John Naylor writes:
> On Wed, Jun 1, 2022 at 2:57 AM Robert Haas wrote:
>> ... So we can fix this by:
>> 1. Using a relative pointer value other than 0 to represent a null
>> pointer. Andres suggested (Size) -1.
>> 2. Not storing the free page manager for the DSM in the main shared
>> memory
On Wed, Jun 1, 2022 at 2:57 AM Robert Haas wrote:
> We do use fpm_segment_base(), but that accidentally fails
> to break, because instead of using relptr_access() it drills right
> through the abstraction and doesn't have any kind of special case for
> 0. So we can fix this by:
>
> 1. Using a
At Wed, 01 Jun 2022 11:42:01 +0900 (JST), Kyotaro Horiguchi
wrote in
me> At Tue, 31 May 2022 16:10:05 -0400, Tom Lane wrote in
me> tgl> Robert Haas writes:
me> tgl> > Yeah, so when I created this stuff in the first place, I figured that
me> tgl> > it wasn't a problem if we reserved relptr ==
At Tue, 31 May 2022 15:57:14 -0400, Robert Haas wrote
in
> 1. Using a relative pointer value other than 0 to represent a null
> pointer. Andres suggested (Size) -1.
I thought that relptr as a part of DSM so the use of offset=0 is
somewhat illegal. But I like this. We can fix this by this
At Tue, 31 May 2022 16:10:05 -0400, Tom Lane wrote in
tgl> Robert Haas writes:
tgl> > Yeah, so when I created this stuff in the first place, I figured that
tgl> > it wasn't a problem if we reserved relptr == 0 to mean a NULL pointer,
tgl> > because you would never have a relative pointer
Robert Haas writes:
> On Tue, May 31, 2022 at 6:14 PM Tom Lane wrote:
>> However, now that I've corrected that mistaken image ... I wonder if
>> it could make sense to redefine relptr as self-relative? That ought
>> to provide some notational savings since you'd only need to carry
>> around the
On Tue, May 31, 2022 at 6:14 PM Tom Lane wrote:
> However, now that I've corrected that mistaken image ... I wonder if
> it could make sense to redefine relptr as self-relative? That ought
> to provide some notational savings since you'd only need to carry
> around the relptr's own address not
Robert Haas writes:
> Seems backwards to me. A relative pointer is supposed to point to
> something inside some range of memory, like a DSM gment -- it can
> never be legally used to point to anything outside that segment. So it
> seems to me that you could perfectly legally point to the second
On Tue, May 31, 2022 at 5:52 PM Tom Lane wrote:
> Thomas Munro writes:
> > Count we make the relptrs 1-based, so that 0 is reserved as a sentinel
> > that has the nice memset(0) property?
>
> Hm ... almost. A +1 offset would mean that zero is ambiguous with a
> pointer to the byte just before
Thomas Munro writes:
> Count we make the relptrs 1-based, so that 0 is reserved as a sentinel
> that has the nice memset(0) property?
Hm ... almost. A +1 offset would mean that zero is ambiguous with a
pointer to the byte just before the relptr. Maybe that case never
arises in practice, but
On Wed, Jun 1, 2022 at 9:09 AM Tom Lane wrote:
> Robert Haas writes:
> > Could it use something other than its own address as the base address?
>
> Hmm, maybe we could make something of that idea ...
>
> > One way to do this would be to put it at the *end* of the
> > "Preallocated DSM" space,
Robert Haas writes:
> Could it use something other than its own address as the base address?
Hmm, maybe we could make something of that idea ...
> One way to do this would be to put it at the *end* of the
> "Preallocated DSM" space, rather than the beginning.
... but that way doesn't sound
On Tue, May 31, 2022 at 4:32 PM Thomas Munro wrote:
> This FPM isn't in a DSM. (It happens to have DSMs *inside it*,
> because I'm using it as a separate DSM allocator: instead of making
> them with dsm_impl.c mechanisms, this one recycles space from the main
> shmem area). I view FPM as a
On Tue, May 31, 2022 at 4:10 PM Tom Lane wrote:
> Seems like that in itself is a a lousy idea. Either the code should
> respect the abstraction, or it shouldn't be declaring the variable
> as a relptr in the first place.
Yep. I think it should be respecting the abstraction, but the 2016
version
On Wed, Jun 1, 2022 at 8:10 AM Tom Lane wrote:
> Robert Haas writes:
> > So we can fix this by:
> > 1. Using a relative pointer value other than 0 to represent a null
> > pointer. Andres suggested (Size) -1.
> > 2. Not storing the free page manager for the DSM in the main shared
> > memory
Robert Haas writes:
> Yeah, so when I created this stuff in the first place, I figured that
> it wasn't a problem if we reserved relptr == 0 to mean a NULL pointer,
> because you would never have a relative pointer pointing to the
> beginning of a DSM, because it would probably always start with
On Thu, May 19, 2022 at 11:00 PM Kyotaro Horiguchi
wrote:
> The path is taken only when a valid value is given to the
> parameter. If we don't use preallocated dsm, it is initialized
> elsewhere. In those cases the first bytes of the base address (the
> second parameter of
At Fri, 20 May 2022 12:00:14 +0900 (JST), Kyotaro Horiguchi
wrote in
> At Thu, 19 May 2022 17:16:03 -0400, Tom Lane wrote in
> > Justin Pryzby writes:
> > > ./tmp_install/usr/local/pgsql/bin/postgres -D
> > > ./src/test/regress/tmp_check/data -c min_dynamic_shared_memory=1MB
> > > TRAP:
At Thu, 19 May 2022 17:16:03 -0400, Tom Lane wrote in
> Justin Pryzby writes:
> > ./tmp_install/usr/local/pgsql/bin/postgres -D
> > ./src/test/regress/tmp_check/data -c min_dynamic_shared_memory=1MB
> > TRAP: FailedAssertion("val > base", File:
> > "../../../../src/include/utils/relptr.h",
Justin Pryzby writes:
> ./tmp_install/usr/local/pgsql/bin/postgres -D
> ./src/test/regress/tmp_check/data -c min_dynamic_shared_memory=1MB
> TRAP: FailedAssertion("val > base", File:
> "../../../../src/include/utils/relptr.h", Line: 67, PID: 21912)
Yeah, I see it too.
> It looks like this may
./tmp_install/usr/local/pgsql/bin/postgres -D ./src/test/regress/tmp_check/data
-c min_dynamic_shared_memory=1MB
TRAP: FailedAssertion("val > base", File:
"../../../../src/include/utils/relptr.h", Line: 67, PID: 21912)
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