Re: Memory trashing? Virtual memory question.

In article <f9e2a709183796c9cee0d60d24b0cf89@www.novabbs.com>,
mhx <mhx@iae.nl> wrote:

On Tue, 24 Sep 2024 12:20:42 +0000, albert@spenarnc.xs4all.nl wrote:
[..]

The following result up to 8 Gbyte are more sensible,
up to 8 Gbyte the second time is faster.
>
root@cherry:/home/albert/PROJECT/ciforths/ciforth# nice -20 lina16G++
WANT ELAPSED
....
 OK
MARK-TIME HERE 1,000,000,000 ERASE ELAPSED .mS
 537.777mS  OK
MARK-TIME HERE 1,000,000,000 ERASE ELAPSED .mS
 253.468mS  OK
MARK-TIME HERE 1,000,000,000 ERASE ELAPSED .mS
 257.628mS  OK
MARK-TIME HERE 2,000,000,000 ERASE ELAPSED .mS
 781.149mS  OK
MARK-TIME HERE 2,000,000,000 ERASE ELAPSED .mS
 503.593mS  OK
MARK-TIME HERE 4,000,000,000 ERASE ELAPSED .mS
 1916.234mS  OK
MARK-TIME HERE 4,000,000,000 ERASE ELAPSED .mS
 1554.072mS  OK
MARK-TIME HERE 8,000,000,000 ERASE ELAPSED .mS
 8059.426mS  OK
MARK-TIME HERE 8,000,000,000 ERASE ELAPSED .mS
 5519.860mS  OK

>
This is exactly the problem that I encountered on
Windows: allocating GBytes of memory is a lot faster
the second time you do it, which points to an OS
memory-management feature. For me it happened when
the allocated memory size was reaching 1GB on a 32GB
system with 20GB still free, so your Linux numbers are
actually quite good.
>
I hoped to  improve matters with the Working-Set
size (which is explicitly shown on Windows 11's
Task manager) but was not successful at the time
(will look again).

Hebish explained it for a great deal.
Clearing a 16 Gbyte area was done with with a large
fraction of memory somehow used.
free reveals a 10 Gbyte memory available.
That nicely explains the discrepancy between 8 Gbyte
and 16 Gbyte clearance.

>
-marcel

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