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Operating Systems Linux Increasing total data size per file system request for block drivers Post 302452803 by amio on Monday 13th of September 2010 06:14:28 AM
Old 09-13-2010
Question Increasing total data size per file system request for block drivers

Hi All,

I am writing a block driver for a 2GB SD card where i get the total amount of data per request as follows:

Code:
struct request *req;
uint card_addr,total_bytes;
struct request_queue *rq = BlkDev->queue;
 
req = elv_next_request(rq);
..
..
card_addr = req->sector*512;
total_bytes = req->current_nr_sectors*512;

Here, the total_bytes i.e the amount of data per request sent/received by file system is always <= 4KB.Hence it affects the card's read/write performance for large file size as the process needs to be repeated for every 4KB.

Is it like, the linux file system block size is limited to 4KB?
Is there any way to increase the transfer size per request?

Thanks in advance.
-amio

Last edited by pludi; 09-13-2010 at 07:42 AM..
 

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FBB::mlm(3bobcat)                                             OFoldStream manipulator                                            FBB::mlm(3bobcat)

NAME
FBB::mlm - Manipulator modifying left margins of OFoldStream objects SYNOPSIS
#include <bobcat/ofoldstream> or #include <bobcat/ofoldstreambuf> Linking option: -lbobcat DESCRIPTION
The mlm class implements a manipulator that can be inserted into OFoldStream objects to modify the stream's left margin by a requested amount. The request cannot result in a negative left margin value. If a negative left margin would be the arithmetic result of the request then left margin 0 will silently be used. Depending on the tab-setting of the OFoldStream the inserted value represents the number of blank space characters or the number of tab-characters that will be added to the left margin. The request will be processed at the next newline character or std::flush or std::endl manipulator that is inserted into the stream. If a line is still empty once an mlm object and a flush manipulator are inserted into the stream then the new left margin will be effective at the next word inserted into that line (cf., the example section below) A bad_cast exception is thrown when the manipulator is inserted into an ostream that is not using a OFoldStreambuf buffer. NAMESPACE
FBB All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace FBB. INHERITS FROM
- CONSTRUCTOR
o mlm(int addValue): The standard copy constructor is available. MEMBER FUNCTIONS
There are no public or protected member functions in this class. EXAMPLE
#include <iostream> #include <bobcat/ofoldstream> using namespace std; using namespace FBB; int main() { OFoldStream out(cout, 0, 80); out << "hello world (left margin is 0)" << mlm(4) << " " "this uses a 4 character wide left margin " << mlm(-10) << flush << "left margin -6 changed to 0, active on this line "; return 0; } FILES
bobcat/mlm - defines the class interface SEE ALSO
bobcat(7), manipulators(3bobcat), lm(3bobcat), ofoldstream(3bobcat) BUGS
None Reported. DISTRIBUTION FILES
o bobcat_3.01.00-x.dsc: detached signature; o bobcat_3.01.00-x.tar.gz: source archive; o bobcat_3.01.00-x_i386.changes: change log; o libbobcat1_3.01.00-x_*.deb: debian package holding the libraries; o libbobcat1-dev_3.01.00-x_*.deb: debian package holding the libraries, headers and manual pages; o http://sourceforge.net/projects/bobcat: public archive location; BOBCAT
Bobcat is an acronym of `Brokken's Own Base Classes And Templates'. COPYRIGHT
This is free software, distributed under the terms of the GNU General Public License (GPL). AUTHOR
Frank B. Brokken (f.b.brokken@rug.nl). libbobcat1-dev_3.01.00-x.tar.gz 2005-2012 FBB::mlm(3bobcat)
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