Hello Greg, During relocation we are copying data block by block..
On Sun, Mar 15, 2009 at 1:00 AM, Manish Katiyar <[email protected]> wrote: > On Sun, Mar 15, 2009 at 12:57 AM, Greg Freemyer <[email protected]> > wrote: >> On Sat, Mar 14, 2009 at 2:55 PM, Vineet Agarwal >> <[email protected]> wrote: >>> hello Greg, >>> >>> sorry i didn't followed it right >>> >>> Now it's done. this is the output.. >>> >>> [r...@fscops Memcopy]# time (cp /test_256.db /mnt; sync) >>> real 0m24.039s >>> user 0m0.022s >>> sys 0m1.566s >>> >> >> Hmmm, still almost twice as fast. >> >> I assume the old time for the kernel module is still valid. ie. >> Adding the 2 calls to sync and the drop_caches logic did not make much >> difference. >> >>>> >> time insmod mmcpy.ko inum=12 (without sync_dirty_buffers) >> real 0m47.679s >> user 0m0.002s >> sys 0m12.838s >>>> >> >> The 12 seconds of system time is very surprising. Please remind me, >> how much data (in bytes) are you reading / writing per iteration? >> >> If it is not a multiple of 4K it can cause big inefficiencies. ie. > > Hi Greg, > > As far as I know, they are reading block by block (in 4K blocksizes). > Do you think readahead on the source inode would help ? We also looked > at the source of "cp" and couldn't find anything special there. > > Thanks - > Manish >> The linux kernel uses a 4K page size and you want to try to use a >> multiple of that for all i/o calls or things go bad from a performance >> perspective. >> >> Greg >> -- >> Greg Freemyer >> Head of EDD Tape Extraction and Processing team >> Litigation Triage Solutions Specialist >> http://www.linkedin.com/in/gregfreemyer >> First 99 Days Litigation White Paper - >> http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf >> >> The Norcross Group >> The Intersection of Evidence & Technology >> http://www.norcrossgroup.com >> > -- >From : Vineet Agarwal -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to [email protected] Please read the FAQ at http://kernelnewbies.org/FAQ
