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From: Jim Geist <velocityboy@gmail.com>
To: Paul Winalski <paul.winalski@gmail.com>
Cc: The Eunuchs Hysterical Society <tuhs@tuhs.org>,
	Noel Chiappa <jnc@mercury.lcs.mit.edu>
Subject: Re: [TUHS] Memory management in Dennis Ritchie's C Compiler
Date: Mon, 17 Aug 2020 14:13:43 -0400	[thread overview]
Message-ID: <CAJohCK+aqCKiYNALrJAdPv=q=+uw8++0oCMR_O10kUJ62m=tVA@mail.gmail.com> (raw)
In-Reply-To: <CABH=_VRRy7mgpgcoayq8v7pW5UL8jcZOH=t=Dt2063=Qn24e-A@mail.gmail.com>

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You beat me to my response. malloc/free are great for long running
processes where memory can't just infinitely increase, but there's a ton of
stuff in a compiler -- types, expressions, symbols -- that survives until
the process exits. There's benefit in both space (because you don't have to
add headers to the blocks as malloc() does, so free() can work) and time to
doing it this way.

On Mon, Aug 17, 2020 at 2:03 PM Paul Winalski <paul.winalski@gmail.com>
wrote:

> On 8/16/20, Noel Chiappa <jnc@mercury.lcs.mit.edu> wrote:
> >
> > The V7 compiler seems to use sbrk() (the system call to manage the
> location of
> > the end of a process' data space), and manage the additional data space
> > 'manually'; it does not seem to use a true generic heap. See gblock() in
> > c01.c:
>
> This is very common in compilers.  Both the DEC/Compaq and Intel
> compilers manage heap memory this way. Each particular phase or pass
> of a compiler tends to build its on set of data structures in heap,
> and then free the whole mess when the phase/pass is done.  malloc/free
> doesn't fit the model very well because you have to free each
> structure individually, and for more persistent structures you don't
> get very good locality of reference.  What works better is to use a
> multitude of mini-heaps that can be freed up all in one go.
>
> -Paul W.
>

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  reply	other threads:[~2020-08-17 18:14 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-17  2:02 Noel Chiappa
2020-08-17 18:02 ` Paul Winalski
2020-08-17 18:13   ` Jim Geist [this message]
2020-08-17 18:48     ` Paul Winalski
2020-08-17 19:08       ` Jim Geist
2020-08-17 19:28         ` Paul Winalski
2020-08-17 19:35           ` Jim Geist
2020-08-17 19:41             ` Richard Salz
2020-08-17 23:40               ` Steffen Nurpmeso
  -- strict thread matches above, loose matches on Subject: below --
2020-08-27  8:37 Paul Ruizendaal
2020-08-26 15:59 Noel Chiappa
2020-08-26 16:09 ` Warner Losh
2020-08-26 19:13   ` Clem Cole
2020-08-26 16:14 ` Jim Geist
2020-08-26 17:31 ` John Cowan
2020-08-26 13:24 Doug McIlroy
2020-08-26 15:41 ` John Cowan
2020-08-25  9:36 Steve Simon
2020-08-17 22:32 Norman Wilson
2020-08-17 22:55 ` Bakul Shah
2020-08-17 23:12 ` Chet Ramey
2020-08-18  6:33 ` arnold
2020-08-17 19:51 Noel Chiappa
2020-08-17 19:27 Noel Chiappa
2020-08-17 19:30 ` Larry McVoy
2020-08-17 19:44   ` Dan Halbert
2020-08-17 19:50   ` Paul Winalski
2020-08-17 22:05     ` Arthur Krewat
2020-08-18  0:52 ` Rob Gingell
2020-08-15 21:50 Dibyendu Majumdar
2020-08-16 15:20 ` arnold
2020-08-16 15:27   ` Jim Geist
2020-08-17 16:13 ` Dan Cross
2020-08-17 20:16   ` Dibyendu Majumdar
2020-08-17 20:34     ` Paul Winalski
2020-08-17 20:43       ` Dibyendu Majumdar
2020-08-17 21:05         ` Warner Losh
2020-08-17 22:47         ` Dave Horsfall
2020-08-17 23:06           ` Nemo Nusquam
2020-08-17 21:29     ` Dibyendu Majumdar
2020-08-24 15:58     ` Dan Cross
2020-08-24 17:08       ` John Cowan
2020-08-24 17:15         ` Clem Cole
2020-08-24 17:24           ` Clem Cole
2020-08-24 17:20         ` Dan Cross
2020-08-25 23:06           ` Arthur Krewat

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