Hello Gentleman, This is a development of "percpu_ida" library. I named it "percpu_tags" to simplify review, since most of "percpu_ida" code has gone and a diff would not be informative. While the concept of per-cpu arrays is is preserved, the implementation is heavily reworked. The main objective is to improve the "percpu_ida" locking scheme. Here is the list of major differrences between "percpu_ida" and "percpu_tags": * The global freelist has gone. As result, CPUs do not compete for the global lock. * Long-running operatons (scanning thru a cpumask) are executed with local interrupts enabled; * percpu_ida::percpu_max_size limit is eliminated. Instead, the limit is determined dynamically. Depending from how many CPUs are requesting tags each CPU gets a fair share of the tag space; * A tag is attempted to return to the CPU it was allocated on. As result, it is expected the locality of data associated with the tag benefits; The code is largely raw and untested. The reason I am posting is the prototype implementation performs 2-3 times faster than "percpu_ida", so I would like to ensure if it worth going further with this approach or is there a no-go. The performance test is not decent, though. I used "fio" random read against a "null_blk" device sitting on top of "percpu_tags", which is not exactly how "percpu_ida" is used. This is another reason I am posting - an advice on how to properly test is very appreciated. The source code could be found at https://github.com/a-gordeev/linux.git percpu_tags-v0 Thanks! Cc: linux-scsi@xxxxxxxxxxxxxxx Cc: qla2xxx-upstream@xxxxxxxxxx Cc: Nicholas Bellinger <nab@xxxxxxxxxxxxx> Cc: Kent Overstreet <kmo@xxxxxxxxxxxxx> Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx> Alexander Gordeev (2): percpu_tags: Prototype implementation percpu_tags: Use percpu_tags instead of percpu_ida drivers/scsi/qla2xxx/qla_target.c | 6 +- drivers/target/iscsi/iscsi_target_util.c | 6 +- drivers/target/target_core_transport.c | 4 +- drivers/target/tcm_fc/tfc_cmd.c | 8 +- drivers/vhost/scsi.c | 6 +- include/linux/percpu_tags.h | 37 ++ include/target/target_core_base.h | 4 +- lib/Makefile | 2 +- lib/percpu_tags.c | 556 ++++++++++++++++++++++++++++++ 9 files changed, 611 insertions(+), 18 deletions(-) create mode 100644 include/linux/percpu_tags.h create mode 100644 lib/percpu_tags.c -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
