web01.fireside.fmThu, 23 Apr 2026 21:19:49 -0500Fireside (https://fireside.fm)TechSNAP - Episodes Tagged with “Memory”
https://techsnap.systems/tags/memory
Fri, 26 Jul 2019 00:15:00 -0700Systems, Network, and Administration Podcast. Every two weeks TechSNAP covers the stories that impact those of us in the tech industry, and all of us that follow it. Every episode we dedicate a portion of the show to answer audience questions, discuss best practices, and solving your problems.
en-usepisodicSystems, Network, and Administration Podcast. Jupiter BroadcastingSystems, Network, and Administration Podcast. Every two weeks TechSNAP covers the stories that impact those of us in the tech industry, and all of us that follow it. Every episode we dedicate a portion of the show to answer audience questions, discuss best practices, and solving your problems.
noJupiter Broadcasting[email protected]408: Apollo's ARC
https://techsnap.systems/408
2577b50c-e740-46c8-a75b-14f074cb812aFri, 26 Jul 2019 00:15:00 -0700Jupiter BroadcastingfullJupiter BroadcastingWe take a look at the amazing abilities of the Apollo Guidance Computer and Jim breaks down everything you need to know about the ZFS ARC.35:13noWe take a look at the amazing abilities of the Apollo Guidance Computer and Jim breaks down everything you need to know about the ZFS ARC.
Plus an update on ZoL SIMD acceleration, your feedback, and an interesting new neuromorphic system from Intel.
virtualization, openzfs, zfs, kvm, qemu, vhd, qcow, qcow2, ARC, memory, page cache, caching, ZFS on Linux, ZoL, SIMD, floating point, fpu, apollo, apollo anniversary, nasa, retro computing, magnetic core, core rope, AGC, apollo guidance computer, intel, dancing demon, kernel module, loihi, neuromorphic computing, text adventure, punch cards, Margaret Hamilton, neural networks, machine learning, ai, pohoiki, snapshots, sysadmin, trs-80, cloud, Chris Siebenmann, DevOps, TechSNAP
We take a look at the amazing abilities of the Apollo Guidance Computer and Jim breaks down everything you need to know about the ZFS ARC.
Plus an update on ZoL SIMD acceleration, your feedback, and an interesting new neuromorphic system from Intel.
Links:
ZFS On Linux Has Figured Out A Way To Restore SIMD Support On Linux 5.0+ — Those running ZFS On Linux (ZoL) on post-5.0 (and pre-5.0 supported LTS releases) have seen big performance hits to the ZFS encryption performance in particular. That came due to upstream breaking an interface used by ZFS On Linux and admittedly not caring about ZoL due to it being an out-of-tree user. But now several kernel releases later, a workaround has been devised.
Linux 5.0 compat: SIMD compatibility · zfsonlinux/zfs@e5db313 — Restore the SIMD optimization for 4.19.38 LTS, 4.14.120 LTS,
and 5.0 and newer kernels. This is accomplished by leveraging
the fact that by definition dedicated kernel threads never need
to concern themselves with saving and restoring the user FPU state.
Therefore, they may use the FPU as long as we can guarantee user
tasks always restore their FPU state before context switching back
to user space.
Chris's Wiki :: ZFS on Linux still has annoying issues with ARC size — One of the frustrating things about operating ZFS on Linux is that the ARC size is critical but ZFS's auto-tuning of it is opaque and apparently prone to malfunctions, where your ARC will mysteriously shrink drastically and then stick there.
Software woven into wire, Core rope and the Apollo Guidance Computer — One of the first computers to use integrated circuits, the Apollo Guidance Computer was lightweight enough and small enough to fly in space. An unusual feature that contributed to its small size was core rope memory, a technique of physically weaving software into high-density storage.
Virtual Apollo Guidance Computer (AGC) software — Since you are looking at this README file, you are in the "master" branch of the repository, which contains source-code transcriptions of the original Project Apollo software for the Apollo Guidance Computer (AGC) and Abort Guidance System (AGS), as well as our software for emulating the AGC, AGS, and some of their peripheral devices (such as the display-keyboard unit, or DSKY).
The Underappreciated Power of the Apollo Computer - The Atlantic — Without the computers on board the Apollo spacecraft, there would have been no moon landing, no triumphant first step, no high-water mark for human space travel. A pilot could never have navigated the way to the moon, as if a spaceship were simply a more powerful airplane. The calculations required to make in-flight adjustments and the complexity of the thrust controls outstripped human capacities.
Brains scale better than CPUs. So Intel is building brains | Ars Technica — Neuromorphic engineering—building machines that mimic the function of organic brains in hardware as well as software—is becoming more and more prominent. The field has progressed rapidly, from conceptual beginnings in the late 1980s to experimental field programmable neural arrays in 2006, early memristor-powered device proposals in 2012, IBM's TrueNorth NPU in 2014, and Intel's Loihi neuromorphic processor in 2017. Yesterday, Intel broke a little more new ground with the debut of a larger-scale neuromorphic system, Pohoiki Beach, which integrates 64 of its Loihi chips.
Dancing Demon - YouTube — Written in 1979 by Leo Christopherson for the Radio Shack TRS-80 Model I computer. This is the best game ever for at that time.
]]>
We take a look at the amazing abilities of the Apollo Guidance Computer and Jim breaks down everything you need to know about the ZFS ARC.
Plus an update on ZoL SIMD acceleration, your feedback, and an interesting new neuromorphic system from Intel.
Links:
ZFS On Linux Has Figured Out A Way To Restore SIMD Support On Linux 5.0+ — Those running ZFS On Linux (ZoL) on post-5.0 (and pre-5.0 supported LTS releases) have seen big performance hits to the ZFS encryption performance in particular. That came due to upstream breaking an interface used by ZFS On Linux and admittedly not caring about ZoL due to it being an out-of-tree user. But now several kernel releases later, a workaround has been devised.
Linux 5.0 compat: SIMD compatibility · zfsonlinux/zfs@e5db313 — Restore the SIMD optimization for 4.19.38 LTS, 4.14.120 LTS,
and 5.0 and newer kernels. This is accomplished by leveraging
the fact that by definition dedicated kernel threads never need
to concern themselves with saving and restoring the user FPU state.
Therefore, they may use the FPU as long as we can guarantee user
tasks always restore their FPU state before context switching back
to user space.
Chris's Wiki :: ZFS on Linux still has annoying issues with ARC size — One of the frustrating things about operating ZFS on Linux is that the ARC size is critical but ZFS's auto-tuning of it is opaque and apparently prone to malfunctions, where your ARC will mysteriously shrink drastically and then stick there.
Software woven into wire, Core rope and the Apollo Guidance Computer — One of the first computers to use integrated circuits, the Apollo Guidance Computer was lightweight enough and small enough to fly in space. An unusual feature that contributed to its small size was core rope memory, a technique of physically weaving software into high-density storage.
Virtual Apollo Guidance Computer (AGC) software — Since you are looking at this README file, you are in the "master" branch of the repository, which contains source-code transcriptions of the original Project Apollo software for the Apollo Guidance Computer (AGC) and Abort Guidance System (AGS), as well as our software for emulating the AGC, AGS, and some of their peripheral devices (such as the display-keyboard unit, or DSKY).
The Underappreciated Power of the Apollo Computer - The Atlantic — Without the computers on board the Apollo spacecraft, there would have been no moon landing, no triumphant first step, no high-water mark for human space travel. A pilot could never have navigated the way to the moon, as if a spaceship were simply a more powerful airplane. The calculations required to make in-flight adjustments and the complexity of the thrust controls outstripped human capacities.
Brains scale better than CPUs. So Intel is building brains | Ars Technica — Neuromorphic engineering—building machines that mimic the function of organic brains in hardware as well as software—is becoming more and more prominent. The field has progressed rapidly, from conceptual beginnings in the late 1980s to experimental field programmable neural arrays in 2006, early memristor-powered device proposals in 2012, IBM's TrueNorth NPU in 2014, and Intel's Loihi neuromorphic processor in 2017. Yesterday, Intel broke a little more new ground with the debut of a larger-scale neuromorphic system, Pohoiki Beach, which integrates 64 of its Loihi chips.
Dancing Demon - YouTube — Written in 1979 by Leo Christopherson for the Radio Shack TRS-80 Model I computer. This is the best game ever for at that time.
]]>
406: SACK Attack
https://techsnap.systems/406
310be811-6d1b-4463-96f3-8fc9579a5d66Sun, 23 Jun 2019 18:15:00 -0700Jupiter BroadcastingfullJupiter BroadcastingA new vulnerability may be the next 'Ping of Death'; we explore the details of SACK Panic and break down what you need to know.43:33noA new vulnerability may be the next 'Ping of Death'; we explore the details of SACK Panic and break down what you need to know.
Plus Firefox zero days targeting Coinbase, the latest update on Rowhammer, and a few more reasons it's a great time to be a ZFS user.
SACK Panic, TCP, networking, Linux, FreeBSD, security, mss, ping of death, rowhammer, rambleed, RAM, ECC, memory, DRAM, Firefox, backdoor, Mozilla, zero day, sandbox, sandbox escape, targeted attack, cryptocurrency, crypto, ZFS, OpenZFS, TRIM, SSD, encryption, raw send, device removal, DevOps, TechSNAP
A new vulnerability may be the next 'Ping of Death'; we explore the details of SACK Panic and break down what you need to know.
Plus Firefox zero days targeting Coinbase, the latest update on Rowhammer, and a few more reasons it's a great time to be a ZFS user.
Links:
SACK Panic Security Bulletin — Netflix has identified several TCP networking vulnerabilities in FreeBSD and Linux kernels. The vulnerabilities specifically relate to the Maximum Segment Size (MSS) and TCP Selective Acknowledgement (SACK) capabilities. The most serious, dubbed “SACK Panic,” allows a remotely-triggered kernel panic on recent Linux kernels.
Ubuntu SACK Panic Guidance — You should update your kernel to the versions specified below in the Updates section and reboot. Alternatively, Canonical Livepatch updates will be available to mitigate these two issues without the need to reboot.
Red Hat SACK Panic Advisory — Red Hat customers running affected versions of these Red Hat products are strongly recommended to update them as soon as errata are available. Customers are urged to apply the available updates immediately and enable the mitigations as they feel appropriate.
RFC 2018 - TCP Selective Acknowledgment Options — TCP may experience poor performance when multiple packets are lost from one window of data. With the limited information available from cumulative acknowledgments, a TCP sender can only learn about a single lost packet per round trip time. An aggressive sender could choose to retransmit packets early, but such retransmitted segments may have already been successfully received. A Selective Acknowledgment (SACK) mechanism, combined with a selective repeat retransmission policy, can help to overcome these limitations.
Ping of Death — In a nutshell, it is possible to crash, reboot or otherwise kill a large number of systems by sending a ping of a certain size from a remote machine.
RAMBleed — RAMBleed is a side-channel attack that enables an attacker to read out physical memory belonging to other processes. The implications of violating arbitrary privilege boundaries are numerous, and vary in severity based on the other software running on the target machine. As an example, in our paper we demonstrate an attack against OpenSSH in which we use RAMBleed to leak a 2048 bit RSA key.
Digging into the new features in OpenZFS post-Linux migration | Ars Technica — One of the most important new features in 0.8 is Native ZFS Encryption. Until now, ZFS users have relied on OS-provided encrypted filesystem layers either above or below ZFS. While this approach does work, it presented difficulties.
Allan Jude on Twitter — Once the FreeBSDs are upstreamed, everything is changing to 'OpenZFS', including the github organization currently know as 'zfsonlinux'.
Mozilla teases $5-per-month ad-free news subscription — Mozilla has started teasing an ad-free news subscription service, which, for $5 per month, would offer ad-free browsing, audio readouts, and cross-platform syncing of news articles from a number of websites.
]]>
A new vulnerability may be the next 'Ping of Death'; we explore the details of SACK Panic and break down what you need to know.
Plus Firefox zero days targeting Coinbase, the latest update on Rowhammer, and a few more reasons it's a great time to be a ZFS user.
Links:
SACK Panic Security Bulletin — Netflix has identified several TCP networking vulnerabilities in FreeBSD and Linux kernels. The vulnerabilities specifically relate to the Maximum Segment Size (MSS) and TCP Selective Acknowledgement (SACK) capabilities. The most serious, dubbed “SACK Panic,” allows a remotely-triggered kernel panic on recent Linux kernels.
Ubuntu SACK Panic Guidance — You should update your kernel to the versions specified below in the Updates section and reboot. Alternatively, Canonical Livepatch updates will be available to mitigate these two issues without the need to reboot.
Red Hat SACK Panic Advisory — Red Hat customers running affected versions of these Red Hat products are strongly recommended to update them as soon as errata are available. Customers are urged to apply the available updates immediately and enable the mitigations as they feel appropriate.
RFC 2018 - TCP Selective Acknowledgment Options — TCP may experience poor performance when multiple packets are lost from one window of data. With the limited information available from cumulative acknowledgments, a TCP sender can only learn about a single lost packet per round trip time. An aggressive sender could choose to retransmit packets early, but such retransmitted segments may have already been successfully received. A Selective Acknowledgment (SACK) mechanism, combined with a selective repeat retransmission policy, can help to overcome these limitations.
Ping of Death — In a nutshell, it is possible to crash, reboot or otherwise kill a large number of systems by sending a ping of a certain size from a remote machine.
RAMBleed — RAMBleed is a side-channel attack that enables an attacker to read out physical memory belonging to other processes. The implications of violating arbitrary privilege boundaries are numerous, and vary in severity based on the other software running on the target machine. As an example, in our paper we demonstrate an attack against OpenSSH in which we use RAMBleed to leak a 2048 bit RSA key.
Digging into the new features in OpenZFS post-Linux migration | Ars Technica — One of the most important new features in 0.8 is Native ZFS Encryption. Until now, ZFS users have relied on OS-provided encrypted filesystem layers either above or below ZFS. While this approach does work, it presented difficulties.
Allan Jude on Twitter — Once the FreeBSDs are upstreamed, everything is changing to 'OpenZFS', including the github organization currently know as 'zfsonlinux'.
Mozilla teases $5-per-month ad-free news subscription — Mozilla has started teasing an ad-free news subscription service, which, for $5 per month, would offer ad-free browsing, audio readouts, and cross-platform syncing of news articles from a number of websites.