c - Means to allocate contiguous physical memory -

-

i aware c malloc , posix_memaligh 1 can allocate contiguous memory virtual address space of process. however, wondering whether somehow 1 can allocate buffer of physically contiguous memory? investigating side channel attacks exploit l2 cache want sure can access right cache lines..

your best , easiest take @ continuous memory request single "huge" page system. availability of depends on cpu , kernel options (on x86_64 2mb huge pages available , cpus can 1gb pages; other architectures can more flexible this). check out hugepagesize field in /proc/meminfo size of huge pages on setup.

those can accessed in 2 ways:

  1. by means of map_hugetlb flag passed mmap(). way can sure "huge" virtual page corresponds continuous physical memory range. unfortunately, whether kernel can supply "huge" page depends on many factors (current layout of memory utilization, kernel options, etc - see hugepages kernel boot parameter).

  2. by means of mapping file dedicated hugetlb filesystem (see here: http://lwn.net/articles/375096/). hugetlb file system can configure number of huge pages available in advance assurance necessary amount of huge pages available.

the other approach write kernel module allocate continuous physical memory on kernel side , map process' address space on request. approach employed on special purpose hardware in embedded systems. of course, there's still no guarantee kernel side memory allocator able come appropriately sized continuous physical address range, on occasions such address ranges pre-reserved on boot (one dumb approach pass max_addr parameter kernel on boot leave of ram out of kernel's reach).


Comments

Post a Comment

Popular posts from this blog

javascript - Any ideas when Firefox is likely to implement lengthAdjust and textLength? -

-
any ideas when firefox implement lengthadjust andtextlength?..... working svg application. lengthadjust , textlength working fine in chrome not working in fire fox . <svg viewbox = "0 0 500 300" version = "1.1"> <defs> <path id="s3" d="m 10,90 q 100,15 200,70" /> </defs> <g> <text font-size = "20"> <textpath xlink:href="#s3" textlength="205"> short text</textpath> </text> <use xlink:href="#s3" fill="none" stroke="black" stroke-width="1"/> </g> </svg> this implemented in firefox text elements (not textpath or tspan) in case that's ok though can move attribute text element. <svg viewbox = "0 0 500 300" version = "1.1"> <defs>
Read more

matlab - "Contour not rendered for non-finite ZData" -

-
i'm trying plot frequency characteristic equation using ezplot, matlab gives following warning, "contour not rendered non-finite zdata". have used command plot frequency equations warning , plot display empty , not change axis range well. can please help. appreciated. here's code i'm using. % transfer matrix case-i, thin rotor clear all; clc; ei = 1626; l = 0.15; m = 0.44108; = 2.178*10^-4; i_p = 2.205*10^-5; itr = 0.24; i_pr = 0.479; syms p n; f = [1 l*1i l^2/(2*ei)*1i l^3/(6*ei); 0 1 l/ei -l^2/(2*ei)*1i; 0 0 1 -l*1i; 0 0 0 l]; p = [ 1 0 0 0; 0 1 0 0; 0 -it*p^2+i_p*n*p 1 0; -m*p^2 0 0 1]; p_r = [1 0 0 0; 0 1 0 0; 0 -itr*p^2+i_pr*n*p 1 0; -m*p^2 0 0 1]; = f*p*f*p*f*p*f; b = p_r*f*p*f*p*f; r = a(1,2)/a(1,4); a12_p = 0; a22_p = a(2,2)-r*a(2,4); a32_p = a(3,2)-r*a(3,4); a42_p = a(4,2)-r*a(4,4); ap(2,2) = a22_p; ap(3,2) = a32_p; ap(4,2) = a42_p; ap(4,4) = 1; c = b*ap; m = [c(3,2) c(3,4); c(4,2) c(4,
Read more

delphi - Indy UDP Read Contents of Adata -

-
i using indy udp server read string of data. however, not know how work adata parameter. can around converting binary using bytetobin function below , convert hex using bintohex1 . feel stupid , works slow. know how can directly results without 2 conversions? thanks!! here codes: procedure tform1.idudpserver1udpread(athread: tidudplistenerthread; const adata: tidbytes; abinding: tidsockethandle); var buf: tidbytes; buffer: string; data_received: string; begin if bytestostring(adata) <> 'hello' begin buffer := hextostring('00'); setlength(buf, length(buffer)); copytidstring(buffer, buf, 0); abinding.sendto(abinding.peerip, abinding.peerport, buf); data_received := bintohex1(bytetobin(adata[1]) + bytetobin(adata[2]) + bytetobin(adata[3]) + bytetobin(adata[4]) + bytetobin(adata[5]) + bytetobin(adata[6]) + bytetobin(adata[7]) + bytetobin(adata[8]) + bytetobin(adata[9]) + bytetobin(adata[10]) + bytetobin(adata[11
Read more