1. how are kernel/ user spaces and high/low memory related?
The traditional virtual mapping for the kernel in linux x86 is 1 gig of address space for the kernel, 3 gigs of address space for one process. There's also a 128-meg hole punched into the kernel range for hardware reasons, which limits the amount of memory the kernel can actually access to potentially less than the system has installed. Memory the kernel can't map into itself is "high memory".
It can use that 128-meg hole indirectly, at a performance cost.
How this matters to userspace is either less available memory, or a performance cost.
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2. What do they all mean when i have the kernel command line as:
"console=ttyS0,115200
Make /dev/console my serial port, defaulting to 115200 baud. This is handy for kernel debugging since you can log crashdumps that come over a serial port, but can't really log a monitor...
Mount /dev/sda2 as my root partition in read-write mode
Ignore the used-memory ranges the BIOS reports and use these numbers instead. grepping for it finds it in arch/x86/kernel/e820.c
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irqpoll
Some badly broken BIOSes screw up interrupt handlers, giving the wrong interrupt numbers etc etc. Interrupts still happen but may call the wrong handlers, or no handlers. irqpoll is a workaround to check all available handlers to see if they're waiting for an interrupt and service it accordingly. I had a system that needed this, without irqpoll the network card would just cause kernel logs like "IRQ 12, nobody cared".
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2. what do mem and memmap mean in terms of user/kernel space and high/low mem?
The difference to userspace is 128 less megs of memory. high memory is a kernel thing, in userspace the distinction is moot.
Hi,
I am seeing very high kernel usage and very high load averages on my system (Although we are not loading much data to our database). Here is the output of top...does anyone know what i should be looking at?
Thanks,
Lorraine
last pid: 13144; load averages: 22.32, 19.81, 16.78 ... (4 Replies)
Hi All,
Kindly help me in optimizing the server as it displays a great amount of CPU & MEM being utilised when the mysql process executes.
Below are the stats ---
--------------------------------------------------------------------------
# top
15:51:57 up 23:22, 5 users, load average:... (1 Reply)
on the file Ftp'd from the mainframe ,do we have any UNIX command to replace mainframe low and values to space or null.
i tried using tr and it doesn't work ...
Thanks (1 Reply)
Hello, I'm searching for a proper way to let the kernel space ISR(implemented in a kernel module) wake up a user space thread on a hardware interrupt.
Except for sending a real-time signal, is it possible to use a semaphore?
I've searched it on google, but it seems impossible to share a... (0 Replies)
Is it possible to have a bash script pick the highest and lowest values of four variables? I've been googling for this but haven't come up with anything. I have a script that assigns variables ($c0, $c1, $c2, and $c3) based on the coretemps from grep/sed statements of sensors. I'd like to also... (5 Replies)
I recently started working with Linux and wrote my first device driver for a hardware chip controlled by a host CPU running Linux 2.6.x kernel.
1. The user space process makes an IOCTL call with pointer to a user memory buffer.
2. The kernel device driver in the big switch-case of IOCTL,... (1 Reply)
Hi guys,
i have a question about spliting a binary file into 2 chunks.
First chunk with all high bytes and the second one with all low bytes.
What unix tools can i use? And how can this be performed?
I looked in manpages of split and dd but this does not help.
Thanks (2 Replies)
Hello All
I have a system running AIX 61 shared uncapped partition (with 11 physical processors, 24 Virtual 72GB of Memory) .
The output from NMON, vmstat show a high run queue (60+) for continous periods of time intervals, but NO paging, relatively low I/o (6000) , CPU % is 40, Low network.... (9 Replies)
Hi team
I have three physical servers running on Red Hat Enterprise Linux Server release 6.2 with the following memory conditions:
# cat /proc/meminfo | grep -i mem
MemTotal: 8062888 kB
MemFree: 184540 kB
Shmem: 516 kB
and the following swap conditions:
... (6 Replies)