Hi Hadi,
On 2017-11-25 22:43:49 -0500, Hadi Moshayedi wrote: > While doing some tests on REL_10_STABLE, I was getting run-time exceptions > at int8_avg_combine() at the following line: > > state1->sumX = state2->sumX; > > After some debugging, I noticed that palloc()’s alignment is 8-bytes, while > this statement (which moves a __int128 from one memory location to another > memory location) expects 16-byte memory alignments. So when either state1 > or state2 is not 16-byte aligned, this crashes. > > When I disassemble the code, the above statement is translated to a pair of > movdqa and movaps assignments when compiled with -O2: > > movdqa c(%rdx), %xmm0 > movaps %xmm0, c(%rcx) > > Looking at “Intel 64 and IA-32 Architectures Software Developer’s Manual, > Volume 2”, both of these instructions expect 16-byte aligned memory > locations, or a general-protection exception will be generated. Nicely analyzed. [Un]fortunately the bug has already been found and fixed: https://git.postgresql.org/pg/commitdiff/619a8c47da7279c186bb57cc16b26ad011366b73 Will be included in the next set of back branch releases. > diff --git a/src/include/utils/memutils.h b/src/include/utils/memutils.h > index 869c59dc85..2dc59e89cd 100644 > --- a/src/include/utils/memutils.h > +++ b/src/include/utils/memutils.h > @@ -189,7 +189,7 @@ extern MemoryContext SlabContextCreate(MemoryContext > parent, > * Few callers should be interested in this, but tuplesort/tuplestore need > * to know it. > */ > -#define ALLOCSET_SEPARATE_THRESHOLD 8192 > +#define ALLOCSET_SEPARATE_THRESHOLD 16384 Huh, what's that about in this context? Greetings, Andres Freund
