1
vote
1answer
49 views

How is 32bit Linux virtual memory structured in relation to PCIe Base Address Registers

I'm working on a Linux system (32 bit, 4GB RAM) and found some contradictory information about memory addressing in Linux. Am I right with this: Only virtual memory has the differentiation between ...
0
votes
2answers
103 views

Linux memory usage?

We have 1TB of memory on a server which hosts an SAP application. When the app is running the memory usage shown in top is around 700GB. When the app is stopped the memory usage shown in top comes ...
5
votes
1answer
433 views

What is equivalent to Mac's purge in Linux?

In Mac I use purge to free up some memory. What is equivalent to it in Linux(Ubuntu Server)? apt-get install purge gave me nothing. If you are no familiar with Mac's purge here is it's man page: ...
1
vote
0answers
122 views

About Linux Memory Compaction (CONFIG_COMPACTION)

I have a question regarding memory compaction on Linux. Generally compaction is triggered when system cannot satisfy a large contiguous memory allocation. This causes the compaction to run on all ...
2
votes
0answers
48 views

Set up OS and Runnig app using x32-ABI

Intro I just moved to a 64bit installation and I'm experiencing big difference in memory usage ( especially for app like chrome, firefox, mysql and java apps ): - While before 4gb were enough now they ...
0
votes
0answers
77 views

How to cause memory fragmentation on a Linux based embedded device?

Hardware ARM What am I trying to do: Answer: I am trying to create memory fragmentation on a Linux 2.6.31 based swapless embedded device. Why: Answer:I am trying to port some patches to Linux ...
2
votes
0answers
58 views

Why does the kernel boot faster with less memory allocated?

This is not a important question, I'm just curious. Something strange happened, which isn't quiet clear to me: In the kernel command line, the amount of the memory can be set statically with the ...
4
votes
1answer
96 views

Why do the data and code segments completely overlap in Linux?

Context: I'm reading "Understanding the Linux kernel, 3d ed", which uses the 2.6.11 kernel. Question: As I understand, the physical address is obtained by translating the linear address, which is ...
2
votes
1answer
259 views

Know when a memory address is aligned or unaligned

Im getting kernel oops because ppp driver is trying to access to unaligned address (there is a pointer pointing to unaligned address). Im not sure about the meaning of unaligned address. It means not ...
6
votes
0answers
249 views

Allocated Memory difference in xen guests after using Linux 3+ kernel [closed]

Can someone explain to me why there is a memory difference in Guests with the same configuration? Hypervisor: xen 4.2 64 bit VM1: Centos 5.7 with 2.6.18-274.el5xen Assigned memory from xen is ...
1
vote
0answers
170 views

Understanding the Buddy Allocator [closed]

I have a conceptual doubt in understanding the way Linux Kernel manages Free blocks. Here is what I interpreted through reading so far. The Buddy Allocator implementation is allocation scheme that ...
-1
votes
1answer
39 views

get Various types of address used [closed]

How to get various address ranges of a running machine or a crash dump? User virtual address Physical address Bus address Kernel logical address Kernel virtual address I don't need the bus ...
0
votes
1answer
130 views

“Acpi-State” in slabtop's output gets increased — what is it? Is it a bug?

Since boot it gets increased occupying even more RAM than anything else: Active / Total Objects (% used) : 680608 / 719176 (94.6%) Active / Total Slabs (% used) : 17390 / 17390 (100.0%) ...
0
votes
1answer
808 views

Invoking memory compaction on linux 2.6.35 kernels and beyond

This LWN article about memory compaction indicates that memory compaction can be invoked in the linux kernel by Writing a node number to /proc/sys/vm/compact_node, causing compaction to happen on ...
7
votes
3answers
3k views

Why is the theoretical RAM limit for RHEL 6 128 TB and how is this determined?

I'm studying for RHCSA and am confused by a statement I came across in some training material: There is no practical maximum RAM, as theoretically, you could run 128 TB of RAM on RHEL 6. But ...
1
vote
0answers
337 views

Where does the Linux kernel reside in memory ?

From some book I have, I have in my notes that the Linux kernel resides at 0xc00000000 on 32-bit systems, and is mapped into user space for performance reasons. Is this accurate ? How can I verify ...
6
votes
2answers
1k views

An oom killer thats baffling me

I am not able to understand why would kernel issue this oom killer when I see enough memory is available: Also why are there so many kernel cache pages allocated? I say enough memory is available ...
3
votes
0answers
542 views

How extended (4MB) and regular (4KB) paging coexist?

On x86 architecture, "Extended paging" allows page frames (physical memory) to be 4 MB instead of 4 KB. The book "Understanding the Linux Kernel, 3rd" at chapter 2 "Memory Addressing", sub-chapter ...
7
votes
2answers
2k views

What is the appropriate value of vm.swappiness when using zram?

I'm using zram on my computer as a compressed RAM-backed swap. When the system needs to swap something out, swapping it to a zram-backed swap file is more or less equivalent to compressing that data ...
2
votes
0answers
130 views

Need good ideas about improving any Linux service [closed]

I have a project assigned to me by OS teacher to choose any Linux service and improve it. Currently I am totally blank in this. I am not sure which service should I use which can easily be implemented ...
5
votes
1answer
3k views

Why does Linux show both more and less memory than I physically have installed?

I know about swap - this question isn't about that. In dmesg, the Linux (x86-64) kernel tells me this about how much memory I have: [ 0.000000] Memory: 3890880k/4915200k available (6073k kernel ...