I am using RHEL 5.1. Sorry for not being clear. I wil give this a try today when I go back to class. But I was just curious why this was happening. How would one disable "block merge" efficiency? Has this feature been added recently? On Thu, Jan 20, 2011 at 12:28 AM, Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx> wrote: > Hi... > > On Thu, Jan 20, 2011 at 10:36, Mag Gam <magawake@xxxxxxxxx> wrote: >> Running on Redhat 5.1 if I do, > > Are you sure you're using that archaic distro? Or are you talking > about RHEL 5.1? > >> dd bs=1024 count=1000000 if=/dev/zero of=/dev/null >> >> I get around 30Gb/sec > > Hm, mine is: > $ dd bs=1024 count=1000000 if=/dev/zero of=/dev/null > 1000000+0 records in > 1000000+0 records out > 1024000000 bytes (1.0 GB) copied, 1.12169 seconds, 913 MB/s > > This is on 2.6.36 SMP kernel compiled with gcc version 4.1.2 20080704 > (Red Hat 4.1.2-48). > >> >> However, when I do this with 2.6.37 I get close to 5GB/sec > > what if you use another blocksize, let's say 4K or even 32K? here's > mine (again): > $ dd bs=4K count=1000000 if=/dev/zero of=/dev/null > 1000000+0 records in > 1000000+0 records out > 4096000000 bytes (4.1 GB) copied, 1.31167 seconds, 3.1 GB/s > > $ dd bs=32K count=1000000 if=/dev/zero of=/dev/null > 1000000+0 records in > 1000000+0 records out > 32768000000 bytes (33 GB) copied, 4.91775 seconds, 6.7 GB/s > > see the difference? > > IMHO it's a matter of what I call "block merge efficiency"....the more > you stuff pages (that fits into a "magic" number), the faster I/O you > got. > > -- > regards, > > Mulyadi Santosa > Freelance Linux trainer and consultant > > blog: the-hydra.blogspot.com > training: mulyaditraining.blogspot.com > _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
