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Avoid Host side PCI bandwidth bottleneck and hint FW to do Write buffering using RaidFlag MR_RAID_FLAGS_IO_SUB_TYPE_LDIO_BW_LIMIT. Once IO is landed in FW with MR_RAID_FLAGS_IO_SUB_TYPE_LDIO_BW_LIMIT, it will do single DMA from host and buffer the Write operation. On back end, FW will DMA same buffer to the Mirror and Data Arm. This will improve large block IO performance which bottleneck due to Host side PCI bandwidth limitation. Consistent ~4000MB T.P for 256K Block size is expected performance numbers. IOPS for small Block size should be on par with Disk performance. (E.g 42 SAS Disk in JBOD mode gives 3700MB T.P. Same Drive used in R1 WT mode, should give ~1800MB T.P) Using this patch 24 R1 VDs (HDD) gives below performance for Sequential Write. Without this patch, we cannot reach above 3200MB (Throughput is in MB.) Block Size 50% 256K and 50% 4K 100% 256K 4K 3100 2030 8K 3140 2740 16K 3140 3140 32K 3400 3240 64K 3500 3700 128K 3870 3870 256K 3920 3920 Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com> Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Reviewed-by: Tomas Henzl <thenzl@redhat.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.