Path: ...!feeds.phibee-telecom.net!2.eu.feeder.erje.net!feeder.erje.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Stephen Fuld <sfuld@alumni.cmu.edu.invalid>
Newsgroups: comp.arch
Subject: Re: Architectural implications of locate mode I/O
Date: Thu, 1 Aug 2024 22:58:16 -0700
Organization: A noiseless patient Spider
Lines: 48
Message-ID: <v8hsho$2alm0$2@dont-email.me>
References: <v61jeh$k6d$1@gal.iecc.com> <v6anes$3mvnv$1@dont-email.me>
 <v8ep4o$1ra0d$2@dont-email.me> <v8f5vc$1lec1$1@dont-email.me>
 <v8gt2o$63j$1@gal.iecc.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Date: Fri, 02 Aug 2024 07:58:16 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="0dfdc06a3db5844c0ef7f71f039cee4b";
	logging-data="2447040"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19pRZ7dkvnArO16coV6cagj0GiqKI1EiyU="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:UrUSX+yI9E8KZBbpH2HmNzBEA/A=
In-Reply-To: <v8gt2o$63j$1@gal.iecc.com>
Content-Language: en-US
Bytes: 2967

On 8/1/2024 2:01 PM, John Levine wrote:
> According to Stephen Fuld  <sfuld@alumni.cmu.edu.invalid>:
>> On 7/31/2024 6:41 PM, Lawrence D'Oliveiro wrote:
>>> On Sat, 6 Jul 2024 06:15:56 -0000 (UTC), Stephen Fuld wrote:
>>>
>>>> As you posted below, the whole PDS search stuff could easily be a
>>>> disaster.  Even with moremodest sized PDSs, it was inefficient has
>>>> hell.
>>>
>>> Would locate mode have helped with this?
>>
>> No.  The problem was that the PDS search was a linear search of records
>> on the disk drive i.e. typically multiple disk revolutions), and
>> furthermore, it required (until the fast PDS search came along) that the
>> host channel take action on each disk record checked, even the ones that
>> didn't match, including resending the search argument to the disk
>> controller.
>>
>> This has nothing to do with locate mode.
> 
> He's made it painfully clear that he doesn't understand the relative
> speed of CPUs and disks, or the costs of multiple I/O buffers on
> systems with small memories, particularly back in the 1960s when this
> stuff was being designed. Nor how records in COBOL data divisions were
> designed so implementations could read and write file records directly
> from and to the buffers, and the IOCS of the era enabled that in COBOL
> and other languages.

I believe you are right about that.


> 
> Perhaps this would be a good time to stop taking the bait. 

Perhaps you are right again, but something about hope springs eternal, 
and I couldn't resist pointing out the problems with the whole PDS 
search mechanism.

> I thought
> this silly argument was over a month ago.

Again, you may be right.  We'll see,



-- 
  - Stephen Fuld
(e-mail address disguised to prevent spam)