13816c768d
virtio_scsi can really use this, to avoid the current hack of copying the whole sg array. Some other things get slightly neater, too. This causes a slowdown in virtqueue_add_buf(), which is implemented as a wrapper. This is addressed in the next patches. for i in `seq 50`; do /usr/bin/time -f 'Wall time:%e' ./vringh_test --indirect --eventidx --parallel --fast-vringh; done 2>&1 | stats --trim-outliers: Before: Using CPUS 0 and 3 Guest: notified 0, pinged 39009-39063(39062) Host: notified 39009-39063(39062), pinged 0 Wall time:1.700000-1.950000(1.723542) After: Using CPUS 0 and 3 Guest: notified 0, pinged 39062-39063(39063) Host: notified 39062-39063(39063), pinged 0 Wall time:1.760000-2.220000(1.789167) Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Reviewed-by: Wanlong Gao <gaowanlong@cn.fujitsu.com> Reviewed-by: Asias He <asias@redhat.com>
189 lines
4.5 KiB
C
189 lines
4.5 KiB
C
#ifndef SCATTERLIST_H
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#define SCATTERLIST_H
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#include <linux/kernel.h>
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struct scatterlist {
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unsigned long page_link;
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unsigned int offset;
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unsigned int length;
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dma_addr_t dma_address;
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};
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/* Scatterlist helpers, stolen from linux/scatterlist.h */
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#define sg_is_chain(sg) ((sg)->page_link & 0x01)
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#define sg_is_last(sg) ((sg)->page_link & 0x02)
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#define sg_chain_ptr(sg) \
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((struct scatterlist *) ((sg)->page_link & ~0x03))
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/**
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* sg_assign_page - Assign a given page to an SG entry
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* @sg: SG entry
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* @page: The page
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*
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* Description:
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* Assign page to sg entry. Also see sg_set_page(), the most commonly used
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* variant.
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*
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**/
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static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
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{
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unsigned long page_link = sg->page_link & 0x3;
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/*
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* In order for the low bit stealing approach to work, pages
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* must be aligned at a 32-bit boundary as a minimum.
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*/
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BUG_ON((unsigned long) page & 0x03);
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#ifdef CONFIG_DEBUG_SG
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BUG_ON(sg->sg_magic != SG_MAGIC);
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BUG_ON(sg_is_chain(sg));
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#endif
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sg->page_link = page_link | (unsigned long) page;
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}
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/**
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* sg_set_page - Set sg entry to point at given page
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* @sg: SG entry
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* @page: The page
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* @len: Length of data
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* @offset: Offset into page
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*
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* Description:
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* Use this function to set an sg entry pointing at a page, never assign
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* the page directly. We encode sg table information in the lower bits
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* of the page pointer. See sg_page() for looking up the page belonging
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* to an sg entry.
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*
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**/
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static inline void sg_set_page(struct scatterlist *sg, struct page *page,
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unsigned int len, unsigned int offset)
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{
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sg_assign_page(sg, page);
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sg->offset = offset;
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sg->length = len;
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}
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static inline struct page *sg_page(struct scatterlist *sg)
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{
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#ifdef CONFIG_DEBUG_SG
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BUG_ON(sg->sg_magic != SG_MAGIC);
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BUG_ON(sg_is_chain(sg));
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#endif
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return (struct page *)((sg)->page_link & ~0x3);
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}
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/*
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* Loop over each sg element, following the pointer to a new list if necessary
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*/
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#define for_each_sg(sglist, sg, nr, __i) \
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for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))
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/**
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* sg_chain - Chain two sglists together
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* @prv: First scatterlist
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* @prv_nents: Number of entries in prv
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* @sgl: Second scatterlist
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*
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* Description:
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* Links @prv@ and @sgl@ together, to form a longer scatterlist.
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*
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**/
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static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
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struct scatterlist *sgl)
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{
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/*
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* offset and length are unused for chain entry. Clear them.
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*/
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prv[prv_nents - 1].offset = 0;
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prv[prv_nents - 1].length = 0;
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/*
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* Set lowest bit to indicate a link pointer, and make sure to clear
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* the termination bit if it happens to be set.
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*/
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prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
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}
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/**
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* sg_mark_end - Mark the end of the scatterlist
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* @sg: SG entryScatterlist
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*
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* Description:
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* Marks the passed in sg entry as the termination point for the sg
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* table. A call to sg_next() on this entry will return NULL.
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*
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**/
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static inline void sg_mark_end(struct scatterlist *sg)
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{
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#ifdef CONFIG_DEBUG_SG
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BUG_ON(sg->sg_magic != SG_MAGIC);
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#endif
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/*
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* Set termination bit, clear potential chain bit
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*/
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sg->page_link |= 0x02;
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sg->page_link &= ~0x01;
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}
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/**
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* sg_unmark_end - Undo setting the end of the scatterlist
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* @sg: SG entryScatterlist
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*
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* Description:
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* Removes the termination marker from the given entry of the scatterlist.
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*
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**/
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static inline void sg_unmark_end(struct scatterlist *sg)
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{
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#ifdef CONFIG_DEBUG_SG
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BUG_ON(sg->sg_magic != SG_MAGIC);
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#endif
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sg->page_link &= ~0x02;
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}
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static inline struct scatterlist *sg_next(struct scatterlist *sg)
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{
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#ifdef CONFIG_DEBUG_SG
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BUG_ON(sg->sg_magic != SG_MAGIC);
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#endif
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if (sg_is_last(sg))
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return NULL;
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sg++;
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if (unlikely(sg_is_chain(sg)))
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sg = sg_chain_ptr(sg);
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return sg;
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}
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static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
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{
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memset(sgl, 0, sizeof(*sgl) * nents);
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#ifdef CONFIG_DEBUG_SG
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{
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unsigned int i;
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for (i = 0; i < nents; i++)
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sgl[i].sg_magic = SG_MAGIC;
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}
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#endif
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sg_mark_end(&sgl[nents - 1]);
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}
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static inline dma_addr_t sg_phys(struct scatterlist *sg)
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{
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return page_to_phys(sg_page(sg)) + sg->offset;
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}
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static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
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unsigned int buflen)
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{
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sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
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}
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static inline void sg_init_one(struct scatterlist *sg,
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const void *buf, unsigned int buflen)
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{
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sg_init_table(sg, 1);
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sg_set_buf(sg, buf, buflen);
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}
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#endif /* SCATTERLIST_H */
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