search for: ioscheduler

...y. Please have a look at what I'm doing and let me know if anybody has any suggestions on how to improve the performance... System specs: ----------------- 2 x 2.8GHz Xeons 6GB RAM 1 3ware 9500S-12 2 x 6-drive, RAID 5 arrays with a stripe size of 256KB. Each array is 2.3TB after formatting. ioscheduler set to use the deadline scheduler. mkfs.ext2 options used: ------------------------ mkfs.ext2 -b 4096 -L /d01 -m 1 -O sparse_super,dir_index -R stride=64 -T largefile /dev/sda1 I'm using a stride size of 64 since the ext2 block size is 4KB and the array stripe size is 256KB (256/4 = 64). Out...

...usr=101.04 minf=19757720.00 cpu sys=740.39 majf=24809.00 ctx=845290443.66 usr=37.25 minf=19349958.33 cpu sys=723.63 majf=27597.33 ctx=850199927.33 usr=35.35 minf=19092343.00 FIO config file: [global] exec_prerun="echo 3 > /proc/sys/vm/drop_caches" group_reporting norandommap ioscheduler=noop thread bs=512 size=4MB direct=1 filename=/dev/vdb numjobs=256 ioengine=aio iodepth=64 loops=3 Signed-off-by: Stefan Hajnoczi <stefanha at linux.vnet.ibm.com> --- Other block drivers (cciss, rbd, nbd) use spin_unlock_irq() so I followed that. To me this seems wrong: blk_run_queue() uses...

...usr=101.04 minf=19757720.00 cpu sys=740.39 majf=24809.00 ctx=845290443.66 usr=37.25 minf=19349958.33 cpu sys=723.63 majf=27597.33 ctx=850199927.33 usr=35.35 minf=19092343.00 FIO config file: [global] exec_prerun="echo 3 > /proc/sys/vm/drop_caches" group_reporting norandommap ioscheduler=noop thread bs=512 size=4MB direct=1 filename=/dev/vdb numjobs=256 ioengine=aio iodepth=64 loops=3 Signed-off-by: Stefan Hajnoczi <stefanha at linux.vnet.ibm.com> --- Other block drivers (cciss, rbd, nbd) use spin_unlock_irq() so I followed that. To me this seems wrong: blk_run_queue() uses...

...ught me to this patch (reverting fixes the issue). Therefore I''d like to come back to that suggested "that way it only affects btrfs" solution. What happens on my system is that all direct I/O requests from userspace are broken up in 4k bio''s and then re-merged by the ioscheduler before reaching the device driver. Eventually that means +30% cpu cost for 64k, probably much more for larger request sizes - Throughput is only affected if there is no cpu left to spare for this additional overhead. A blktrace log is probably the best way to explain this in detail: (sequential 64...

Currently, some new storage devices have the ability to do performance optimizations according to the type of data payload - say, file system metadata, time-stamps, sequential write in some granularity, random write and so on. For example, the latest eMMC 4.5 device can support the so-called ''Context Management'' and ''Data Tag Mechanism'' features. By receiving