Re: The return value of realloc(p,0)

From	Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups	comp.lang.c
Subject	Re: The return value of realloc(p,0)
Date	2023-09-03 01:45 -0700
Organization	A noiseless patient Spider
Message-ID	<86zg23r6fi.fsf@linuxsc.com> (permalink)
References	(4 earlier) <ucqrn0$3dvle$1@dont-email.me> <86wmxas6ty.fsf@linuxsc.com> <ucsejp$3nrkk$5@dont-email.me> <86sf7xspk3.fsf@linuxsc.com> <JCqIM.79177$m8Ke.22576@fx08.iad>

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scott@slp53.sl.home (Scott Lurndal) writes:

> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>
>> Vir Campestris <vir.campestris@invalid.invalid> writes:
>>
>>
>> In a 64-bit address space, there are a lot more addresses than
>> there are bytes of memory, even virtual bytes of memory.  All but
>> a very small fraction of 64-bit addresses cannot map to actual
>> memory, because there is no room on the address bus (figuratively
>> speaking).
>
> Current processors support between 44 and 52 bits of physical
> address, and for the most part, the same on the virtual address
> space as well.    ARMv8 allows the VA space to be anywhere
> from 16 bits to 52 bits on a per-translation-context) basis;
> where smaller VA sizes can significantly decrease translation
> table walk cost (i.e. by skipping levels).
>
> With DDR5 and HBM we're seeing terabytes of DRAM on the bus.

Still plenty of address space left over.

> With CXL (and Intel's PUMA chip) the physical address bus
> will be fully utilized (all 64 bits) in the not so distant
> future, if perhaps sparsely by using higher order bits to
> identify nodes on the fabric.

I think the key word there is sparsely.  A very small
fraction of a 64-bit address space suffices, and that
needn't be all contiguous either - it's easy to handle
a modest number of distinct areas, without too much
burden either in space or time.

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Re: The return value of realloc(p,0) Robert Latest <boblatest@yahoo.com> - 2023-08-30 15:54 +0000
  Re: The return value of realloc(p,0) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-08-30 22:33 -0700
    Re: The return value of realloc(p,0) Vir Campestris <vir.campestris@invalid.invalid> - 2023-08-31 21:03 +0100
      Re: The return value of realloc(p,0) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-01 00:14 -0700
        Re: The return value of realloc(p,0) Vir Campestris <vir.campestris@invalid.invalid> - 2023-09-01 11:32 +0100
          Re: The return value of realloc(p,0) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-01 17:08 +0000
          Re: The return value of realloc(p,0) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-01 11:42 -0700
            Re: The return value of realloc(p,0) scott@slp53.sl.home (Scott Lurndal) - 2023-09-01 19:06 +0000
              Re: The return value of realloc(p,0) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-03 01:45 -0700
                Re: The return value of realloc(p,0) scott@slp53.sl.home (Scott Lurndal) - 2023-09-03 16:12 +0000
                Re: The return value of realloc(p,0) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-03 12:01 -0700
                Re: The return value of realloc(p,0) scott@slp53.sl.home (Scott Lurndal) - 2023-09-03 21:40 +0000
                Re: The return value of realloc(p,0) Spiros Bousbouras <spibou@gmail.com> - 2023-09-03 23:08 +0000
                Re: The return value of realloc(p,0) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-03 16:23 -0700
                Re: The return value of realloc(p,0) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-03 17:01 -0700
                Re: The return value of realloc(p,0) scott@slp53.sl.home (Scott Lurndal) - 2023-09-04 14:22 +0000
                Re: The return value of realloc(p,0) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-05 05:23 -0700
                Re: The return value of realloc(p,0) Vir Campestris <vir.campestris@invalid.invalid> - 2023-09-04 16:40 +0100
            Re: The return value of realloc(p,0) Vir Campestris <vir.campestris@invalid.invalid> - 2023-09-02 21:40 +0100
        Re: The return value of realloc(p,0) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-01 17:03 +0000
          Re: The return value of realloc(p,0) Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2023-09-01 17:57 +0000
            Re: The return value of realloc(p,0) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-01 18:44 +0000
              Re: The return value of realloc(p,0) Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2023-09-01 20:24 +0000
            Re: The return value of realloc(p,0) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-01 11:58 -0700
              Re: The return value of realloc(p,0) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-01 19:14 +0000
                Re: The return value of realloc(p,0) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-03 12:03 -0700
          Re: The return value of realloc(p,0) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-01 11:55 -0700

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