computer architecture – Memory Invalidation and Misses

Assume this particular architecture of a machine. Say we have 4 processors and each processor has its private L1 cache and shared L2 cache. Now if we write to an address in one of the private cache’s of the L1 cache then we Invalidate the blocks in the other private cache which contains the same address. Say P0(processor 0) reads an address 100 and so the block containing it say B0 gets stored in the private cache of P0 and as well as in the shared L2 cache. Now say P2 writes to the location 100. So we need to invalidate the block B0 from the private cache of P0. Now if P0 wants to read from address 100 again it will suffer a miss in its private cache, but will it get HIT or MISS in the L2 cache?

I think it will get HIT. Can anyone confirm.

azure – Is it possible to dump memory from one Ubuntu VM to another?

I’m trying to use Azure VMs to host a game server for me and some friends since spot instances are cheap, but the downside is that they get deallocated/deleted pretty quickly in practice (somewhere like every 30 mins when I was testing). So I’m trying to devise a way to spin up a new spot instance as soon as the old one gets an eviction notice, and then dump the memory from the first VM to the new one so it can carry on as the new game server, all without causing any pauses for the players. Does Ubuntu have built in methods or existing packages for RDMA? Or does anyone know if Azure supports this (I saw mention of RDMA for their HPC sizes but that’s way too expensive for this use case)?

memory – My PC gets frequent random blue screens

As the title says, my PC gets random, frequent blue screens.
My PC is overclocked to the minimal overclock preset, which is handled by a knob on my motherboard.
I stress tested my PC using a program called Aida64 extreme. It only/always occurs when stress testing the “FPU”
Stress testing any of the other components (GPU, SSD, CPU, Memory) does not cause a blue screen to occur. Any advice on what the problem might be?

PC specs: Cooler Master 750w PSU MSI MEG Z390 GODLIKE NZXT kraken x63 I9 9900K MSI RTX 2080s gaming X trio Corsair Vengeance pro 3200MHz Fractal Design R6 Samsung 970 EVO

memory – PC BSOD with minimal overclocking

I need some help understanding what’s going wrong with my overclocking, as this is my first time of doing it. Whenever I overclock my CPU using the overclock preset button on my motherboard it will BSOD. Even on the lowest possible setting. I tried stress testing using Aida64 Extreme and everything (CPU, disks, GPU etc) would work just fine except for the “FPU”, which would make my PC BSOD almost immediately. Any advice?

PC specs: Cooler Master 750w PSU MSI MEG Z390 GODLIKE NZXT kraken x63 I9 9900K MSI RTX 2080s gaming X trio Corsair Vengeance pro 3200MHz Fractal Design R6 Samsung 970 EVO

Extract pre-master keys from memory

I want to get pre-master key from OpenSSL application (in order to decrypt traffic).
Details:

  • OpenSSL version: 1.0.2l, statically linked, no debug symbols
  • I’m able to debug the application (hit breakpoint inside SSL_connect(SSL *s) method)

Is there any way to get the pre-master key from there? I’m using x64dbg. Sorry if that sounds like a newbie question.

filemanager – Accessing Memory Card on Epson WF-7510

When I try to access the memory card in the printer, I am prompted for a password. What password? It seems to accept none that would relate to either the PC or the printer itself and it’s not clear what it wants. Pardon the double-negative but does not accept no password either.

The password popup is pre-populated with my Ubuntu user name and it shows the Domain which is actually the WiFi SSID as I am not using a domain. Neither the user name nor the domain are editable in the popup. I did enable WiFi file sharing on the printer itself and am running Ubuntu 20.10.

testing – How can I set up an a SQLite memory database to improve PHPUnit test speeds?

I’m trying to speed up a functional Drupal test.
Given a test…

...
  public function the_front_page_loads_for_anonymous_users() {
    $this->config('system.site')
      ->set('page.front', '/node')
      ->save(TRUE);

    $this->drupalGet('<front>');

    $assert = $this->assertSession();
    $assert->pageTextContains('Welcome to Drupal');
    $assert->pageTextContains('No front page content has been created yet.');
  }

This test runs really slow against my database … 2+ mins.

If I use a test sqlite database, it drops to around 1.6 mins
<env name="SIMPLETEST_DB" value="sqlite://localhost/logs/test.sqlite"/>

If I use a in-memory database, <env name="SIMPLETEST_DB" value="sqlite://localhost/:memory:"/>, Drupal detects no database and runs install.php

How can I set up an sqlite memory database to improve test speeds?

Why is MEMORYCLERK_SQLGENERAL using so much memory in SQL Server?

I have a production system running SQL Server 2019 Standard edition. It recently had a problem 3 times in 1 day where it became unresponsive until a reboot. Errors seem to point to memory limitations. 32GB is installed and the machine is dedicated to MSSQL. Max Memory set to 26GB.

The best lead I have so far is output of dbcc memorystatus that was automatically dumped to the log along with a FAIL_PAGE_ALLOCATION error. The full output is attached, but this part below caught my eye. It looks like MEMORYCLERK_SQLGENERAL wanted so much memory that it forced normal things like the buffer pool and query memory down to uselessly small levels.

I can’t seem to find any good info on what MEMORYCLERK_SQLGENERAL does, let alone why it would want so much memory.

11/18/2020 15:10:48,spid51,Unknown,MEMORYCLERK_SQLGENERAL (node 0)                  KB
Pages Allocated                            22821672
SM Committed                                      0
SM Reserved                                       0
Locked Pages Allocated                       546740
VM Committed                                  75776
VM Reserved                                12867644
---------------------------------------- ----------
11/18/2020 15:10:48,spid51,Unknown,MEMORYCLERK_SQLBUFFERPOOL (node 0)               KB
Pages Allocated                                3400
SM Committed                                      0
SM Reserved                                       0
Locked Pages Allocated                            0
VM Committed                                      0
VM Reserved                                       0
---------------------------------------- ----------
11/18/2020 15:10:48,spid51,Unknown,MEMORYCLERK_SQLQUERYPLAN (node 0)                KB
Pages Allocated                                3632
SM Committed                                      0
SM Reserved                                       0
Locked Pages Allocated                            0
VM Committed                                      0
VM Reserved                                       0
---------------------------------------- ----------
11/18/2020 15:10:48,spid51,Unknown,MEMORYCLERK_SQLQUERYEXEC (node 0)                KB
Pages Allocated                                1128
SM Committed                                      0
SM Reserved                                       0
Locked Pages Allocated                            0
VM Committed                                      0
VM Reserved                                       0

7 – Drush on server: Error: Allowed memory size issue

I have Drush installed on my Inmotion hosting server.
For one Drupal 7 site, it works just fine but for the other one, which is nearly identical, it doesn’t work so well.
Some commands it allows (like my favourite drush sql-dump or drush cc followed by 5) and but when I do a command drush cc all it throws an out-of-memory issue as shown below:

Drush command terminated abnormally due to an unrecoverable error.                                                                         (error)
Error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 20480 bytes) in
/home/myAccount/public_html/mysite.net/sites/all/modules/views/includes/base.inc, line 129

The issues stemming from the base.inc file are:

after command: drush cc all: on line 129:
$storage($option) = isset($definition('default')) ? $definition('default') : NULL;

The issues stemming from the view.inc file are:

after command: drush cc all: on line 2244:
$this->$field = unserialize($info('serialized default'));

after command: drush cc all: on line 2312:
$this->$field = empty($info('serialize')) ? $data->$field : unserialize($data->$field);

The php.ini files are identical on both sites.
The settings.php files are not identical and I thought it would be resolved by adding the same lines to the ending of the file

ini_set('memory_limit', '512M');
error_reporting(E_ALL);
$conf('error_level') = 2;
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);

but this didn’t solve the problem (even after clearing the cache).

What could cause this problem?