From ac3dd5bd128b1d1ce2a037775766f39d06a4848a Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 22 Jan 2015 12:07:58 -0700 Subject: NVMe: avoid kmalloc/kfree for smaller IO Currently we allocate an nvme_iod for each IO, which holds the sg list, prps, and other IO related info. Set a threshold of 2 pages and/or 8KB of data, below which we can just embed this in the per-command pdu in blk-mq. For any IO at or below NVME_INT_PAGES and NVME_INT_BYTES, we save a kmalloc and kfree. For higher IOPS, this saves up to 1% of CPU time. Signed-off-by: Jens Axboe Reviewed-by: Keith Busch --- include/linux/nvme.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'include/linux/nvme.h') diff --git a/include/linux/nvme.h b/include/linux/nvme.h index 258945fcabf1..19a5d4b23209 100644 --- a/include/linux/nvme.h +++ b/include/linux/nvme.h @@ -132,13 +132,12 @@ struct nvme_ns { * allocated to store the PRP list. */ struct nvme_iod { - void *private; /* For the use of the submitter of the I/O */ + unsigned long private; /* For the use of the submitter of the I/O */ int npages; /* In the PRP list. 0 means small pool in use */ int offset; /* Of PRP list */ int nents; /* Used in scatterlist */ int length; /* Of data, in bytes */ dma_addr_t first_dma; - struct list_head node; struct scatterlist sg[0]; }; -- cgit v1.2.3-55-g7522