logo
down
shadow

What is a Kernel Overhead?


What is a Kernel Overhead?

Content Index :

What is a Kernel Overhead?
Tag : development , By : user152423
Date : November 25 2020, 07:06 PM


Comments
No Comments Right Now !

Boards Message :
You Must Login Or Sign Up to Add Your Comments .

Share : facebook icon twitter icon

Overhead of supporting Floating Point Arithmetic inside the Linux Kernel


Tag : linux , By : TomL
Date : March 29 2020, 07:55 AM
Hope that helps The usual answer is that if the kernel does not use floating point, it does not have to save the floating-point registers on entry to the kernel or restore them on exit. This shaves several hundred cycles off the cost of all system calls.
I do not know if anyone has tried to compare this savings against the performance improvements that might be available if the kernel could make indiscriminate use of those registers. Note that you can use them in the kernel if you take proper care, and this is done in contexts where tremendous speed benefits are available, e.g. using SSE instructions to accelerate memcpy and the like. (Look for calls to kernel_fpu_begin in the Linux sources.)

Accurate way of measuring overhead in kernel space


Tag : linux , By : user158193
Date : March 29 2020, 07:55 AM
wish of those help I think you want more to measure a typical application payload (as Ninjajl's comment suggests, the compilation of the kernel could be a good payload). You probably don't want to measure the overhead inside each syscall itself, or even inside the kernel as a whole.
The reason for this is that most applications spend much more time and resource in user-space than in kernel-land (i.e. syscalls), so overhead inside syscalls is a "second-order" effect and probably don't matter as much. Of course, there are probable exceptions.

How to measure overhead of a kernel launch in CUDA


Tag : cuda , By : Bruce
Date : March 29 2020, 07:55 AM
may help you . How to measure the overhead of a kernel launch in CUDA is dealt with in Section 6.1.1 of the "CUDA Handbook" book by N. Wilt. The basic idea is to launch an empty kernel. Here is a sample code snippet
#include <stdio.h>

__global__ void EmptyKernel() { }

int main() {

    const int N = 100000;

    float time, cumulative_time = 0.f;
    cudaEvent_t start, stop;
    cudaEventCreate(&start);
    cudaEventCreate(&stop);

    for (int i=0; i<N; i++) { 

        cudaEventRecord(start, 0);
        EmptyKernel<<<1,1>>>(); 
        cudaEventRecord(stop, 0);
        cudaEventSynchronize(stop);
        cudaEventElapsedTime(&time, start, stop);
        cumulative_time = cumulative_time + time;

    }

    printf("Kernel launch overhead time:  %3.5f ms \n", cumulative_time / N);
    return 0;
}

Reducing kernel overhead when reading a huge file with lazy bytestrings


Tag : linux , By : user152423
Date : March 29 2020, 07:55 AM
hop of those help? First, it seems like there is something wonky going on with your machine. When I run this program on a 1G file cached in memory or in an tmpfs filesystem (doesn't matter which), the system time is substantially smaller:
1.44user 0.14system 0:01.60elapsed 99%CPU (0avgtext+0avgdata 50256maxresident)
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>

#define BUFLEN (1024*1024)
char buffer[BUFLEN];

int
main()
{
        int nulls = 0;
        int fd = open("/dev/shm/testfile5G.dat", O_RDONLY);
        while (read(fd, buffer, BUFLEN) > 0) {
                for (int i = 0; i < BUFLEN; ++i) {
                        if (!buffer[i]) ++nulls;
                }
        }
        printf("%d\n", nulls);
}
real    0m2.035s
user    0m1.619s
sys     0m0.416s
import Data.Word
import qualified Data.ByteString.Lazy as BSL

main :: IO ()
main = do
  contents <- BSL.readFile "/scratch/buhr/testfile5G.dat"
  print $ BSL.foldl' go 0 contents
    where go :: Int -> Word8 -> Int
          go n 0 = n + 1
          go n _ = n
real    0m8.411s
user    0m7.966s
sys     0m0.444s
import System.Posix.IO
import Foreign.Ptr
import Foreign.ForeignPtr
import MMAP
import qualified Data.ByteString as BS
import qualified Data.ByteString.Internal as BS

-- exact length of file
len :: Integral a => a
len = 5368709120

main :: IO ()
main = do
  fd <- openFd "/scratch/buhr/testfile5G.dat" ReadOnly Nothing defaultFileFlags
  ptr <- newForeignPtr_ =<< castPtr <$>
    mmap nullPtr len protRead (mkMmapFlags mapPrivate mempty) fd 0
  let contents = BS.fromForeignPtr ptr 0 len
  print $ BS.foldl' (+) 0 contents
real    0m7.972s
user    0m7.791s
sys     0m0.181s
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>

size_t len = 5368709120;

int
main()
{
        int nulls = 0;
        int fd = open("/scratch/buhr/testfile5G.dat", O_RDONLY);
        char *p = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
        for (int i = 0; i < len; ++i) {
                if (!p[i]) ++nulls;
        }
        printf("%d\n", nulls);
}
real    0m1.888s
user    0m1.708s
sys     0m0.180s

Minimal overhead way of intercepting system calls without modifying the kernel


Tag : c , By : jrf
Date : March 29 2020, 07:55 AM
Related Posts Related QUESTIONS :
  • Sleep from within an Informix SPL procedure
  • License Models
  • Rational Purify failing to jump to memory leaks
  • Telligent's Community Server
  • Do people use the Hungarian Naming Conventions in the real world?
  • Memcached chunk limit
  • How do you pull the URL for an ASP.NET web reference from a configuration file in Visual Studio 2008?
  • How to add CVS directories recursively
  • Web App Beta
  • Virtual machine supporting multiple displays
  • LINQ to SQL strings to enums
  • How do I configure eclipse (zend studio 6) to hint and code complete several languages?
  • Recommended Fonts for Programming?
  • Automating VMWare or VirtualPC
  • How do I use more than one OpenID?
  • Domain Specific Language resources
  • Vista or XP for Dev Machine
  • Where can I get the Windows Workflow "wca.exe" application?
  • How to learn ADO.NET
  • What is a good barebones CMS or framework?
  • What's the Developer Express equivalent of System.Windows.Forms.LinkButton?
  • Is it acceptable for invalid XHTML?
  • Anyone soloing using fogbugz?
  • Using MBUnit in TeamCity
  • How to setup a crontab to execute at specific time
  • Linking two Office documents
  • How can I detect if a browser is blocking a popup?
  • Apply filter to t-foreach
  • Lotus Notes convert formula to agent
  • Problem with configuration of odoo for working with pycharm
  • Unexpected number of arguments when calling EM_JS function
  • What does the function state_fidelity() do in Qiskit?
  • Azure function with IoT Hub trigger get send device
  • Cluster similar words using word2vec
  • Add elements into an array then find distinct,
  • Angular8 - error TS2304: Cannot find name
  • Manually polling streams in future implementation
  • How do you perform receipt validation for Android on Xamarin Forms
  • What is the rule behind instruction count in Intel PIN?
  • How to draw some text when click a button in wxWidgets?
  • Restrict entity types in Spacy NER
  • How to animate CN1 Slider progress on load
  • Issue with bwa mem process not running on all output files from previous process
  • Delete videos from playlist using YouTube API
  • How to restart the Hyperledger Composer Playground locally
  • How to configure email alerts in Zabbix Server?
  • Simulator is not working for smart home action with all configured session
  • How parse data using join on Objection.js
  • Assign an array to a property in a Chapel Class
  • Netlogo: How can I obtain the accumulate value in Netlogo?
  • How to populate datasource for listview using api response in react native?
  • Why does gmail API when using history.list method send message ids without the field what action has been preformed on t
  • How to run an append query in ms access vba as part of a transaction
  • Wrong dates shown in Jekyll-based blog
  • How to concatenate two document lists in a webMethods flow service?
  • How to properly set up a site map addition in a customization project
  • IBM Content Collector error calling external Web Service
  • Is (0*1*)* equal to (0 | 1)*?
  • How do I configure phpMyAdmin to start with a blank sql query from the SQL tab?
  • "Objects are not valid as a React child" Redux error when conditionally connecting a component?
  • shadow
    Privacy Policy - Terms - Contact Us © scrbit.com