On Fri, 8 Aug 2008, Jens Axboe wrote: > On Fri, Aug 08 2008, FUJITA Tomonori wrote: > > On Fri, 8 Aug 2008 08:15:37 +0200 > > Jens Axboe <jens.axboe@xxxxxxxxxx> wrote: > > > > > > BTW, we also wait for your verdict on: > > > > > > > > http://marc.info/?t=121611935500002&r=1&w=2 > > > > > > I've always hated the iommu virtual merging complexity. My plan is to > > > rip it out. > > > > No complaint from me. I'm just happy to see the verdict at length. > > Mikulas, you had a patch for this. Can you strip out the arch bits and > just send me the block bits? The arch bits should go in via the arch > maintainers. > > The iommu code may still do virtual merging, it would be silly not to do > that if possible. Now that later kernels expose the necessary parameters > at that level as well, it's perfectly feasible. Here I'm sending the first one, it removes virtual merge accounting from blk-merge.c (it acts as if all architectures undefined BIO_VMERGE_BOUNDARY). I also created second patch that removes bi_hw_segments field from struct bio and struct request. The next task would be to remove nr_hw_segments from the request_queue, but it will require changing the drivers. Mikulas --- Remove virtual merge accounting. Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> --- block/blk-merge.c | 76 ++++------------------------------------------------ fs/bio.c | 6 +--- include/linux/bio.h | 15 ---------- 3 files changed, 8 insertions(+), 89 deletions(-) Index: linux-2.6.26-devel/block/blk-merge.c =================================================================== --- linux-2.6.26-devel.orig/block/blk-merge.c 2008-07-15 23:29:39.000000000 +0200 +++ linux-2.6.26-devel/block/blk-merge.c 2008-08-08 18:46:57.000000000 +0200 @@ -66,7 +66,7 @@ void blk_recalc_rq_segments(struct reque */ high = page_to_pfn(bv->bv_page) > q->bounce_pfn; if (high || highprv) - goto new_hw_segment; + goto new_segment; if (cluster) { if (seg_size + bv->bv_len > q->max_segment_size) goto new_segment; @@ -74,8 +74,6 @@ void blk_recalc_rq_segments(struct reque goto new_segment; if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv)) goto new_segment; - if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len)) - goto new_hw_segment; seg_size += bv->bv_len; hw_seg_size += bv->bv_len; @@ -83,17 +81,11 @@ void blk_recalc_rq_segments(struct reque continue; } new_segment: - if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) && - !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len)) - hw_seg_size += bv->bv_len; - else { -new_hw_segment: - if (nr_hw_segs == 1 && - hw_seg_size > rq->bio->bi_hw_front_size) - rq->bio->bi_hw_front_size = hw_seg_size; - hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len; - nr_hw_segs++; - } + if (nr_hw_segs == 1 && + hw_seg_size > rq->bio->bi_hw_front_size) + rq->bio->bi_hw_front_size = hw_seg_size; + hw_seg_size = bv->bv_len; + nr_hw_segs++; nr_phys_segs++; bvprv = bv; @@ -146,22 +138,6 @@ static int blk_phys_contig_segment(struc return 0; } -static int blk_hw_contig_segment(struct request_queue *q, struct bio *bio, - struct bio *nxt) -{ - if (!bio_flagged(bio, BIO_SEG_VALID)) - blk_recount_segments(q, bio); - if (!bio_flagged(nxt, BIO_SEG_VALID)) - blk_recount_segments(q, nxt); - if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) || - BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size)) - return 0; - if (bio->bi_hw_back_size + nxt->bi_hw_front_size > q->max_segment_size) - return 0; - - return 1; -} - /* * map a request to scatterlist, return number of sg entries setup. Caller * must make sure sg can hold rq->nr_phys_segments entries @@ -299,7 +275,6 @@ int ll_back_merge_fn(struct request_queu struct bio *bio) { unsigned short max_sectors; - int len; if (unlikely(blk_pc_request(req))) max_sectors = q->max_hw_sectors; @@ -316,19 +291,6 @@ int ll_back_merge_fn(struct request_queu blk_recount_segments(q, req->biotail); if (!bio_flagged(bio, BIO_SEG_VALID)) blk_recount_segments(q, bio); - len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size; - if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio)) - && !BIOVEC_VIRT_OVERSIZE(len)) { - int mergeable = ll_new_mergeable(q, req, bio); - - if (mergeable) { - if (req->nr_hw_segments == 1) - req->bio->bi_hw_front_size = len; - if (bio->bi_hw_segments == 1) - bio->bi_hw_back_size = len; - } - return mergeable; - } return ll_new_hw_segment(q, req, bio); } @@ -337,7 +299,6 @@ int ll_front_merge_fn(struct request_que struct bio *bio) { unsigned short max_sectors; - int len; if (unlikely(blk_pc_request(req))) max_sectors = q->max_hw_sectors; @@ -351,23 +312,10 @@ int ll_front_merge_fn(struct request_que q->last_merge = NULL; return 0; } - len = bio->bi_hw_back_size + req->bio->bi_hw_front_size; if (!bio_flagged(bio, BIO_SEG_VALID)) blk_recount_segments(q, bio); if (!bio_flagged(req->bio, BIO_SEG_VALID)) blk_recount_segments(q, req->bio); - if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) && - !BIOVEC_VIRT_OVERSIZE(len)) { - int mergeable = ll_new_mergeable(q, req, bio); - - if (mergeable) { - if (bio->bi_hw_segments == 1) - bio->bi_hw_front_size = len; - if (req->nr_hw_segments == 1) - req->biotail->bi_hw_back_size = len; - } - return mergeable; - } return ll_new_hw_segment(q, req, bio); } @@ -399,18 +347,6 @@ static int ll_merge_requests_fn(struct r return 0; total_hw_segments = req->nr_hw_segments + next->nr_hw_segments; - if (blk_hw_contig_segment(q, req->biotail, next->bio)) { - int len = req->biotail->bi_hw_back_size + - next->bio->bi_hw_front_size; - /* - * propagate the combined length to the end of the requests - */ - if (req->nr_hw_segments == 1) - req->bio->bi_hw_front_size = len; - if (next->nr_hw_segments == 1) - next->biotail->bi_hw_back_size = len; - total_hw_segments--; - } if (total_hw_segments > q->max_hw_segments) return 0; Index: linux-2.6.26-devel/include/linux/bio.h =================================================================== --- linux-2.6.26-devel.orig/include/linux/bio.h 2008-07-15 23:29:39.000000000 +0200 +++ linux-2.6.26-devel/include/linux/bio.h 2008-08-08 18:46:29.000000000 +0200 @@ -26,21 +26,8 @@ #ifdef CONFIG_BLOCK -/* Platforms may set this to teach the BIO layer about IOMMU hardware. */ #include <asm/io.h> -#if defined(BIO_VMERGE_MAX_SIZE) && defined(BIO_VMERGE_BOUNDARY) -#define BIOVEC_VIRT_START_SIZE(x) (bvec_to_phys(x) & (BIO_VMERGE_BOUNDARY - 1)) -#define BIOVEC_VIRT_OVERSIZE(x) ((x) > BIO_VMERGE_MAX_SIZE) -#else -#define BIOVEC_VIRT_START_SIZE(x) 0 -#define BIOVEC_VIRT_OVERSIZE(x) 0 -#endif - -#ifndef BIO_VMERGE_BOUNDARY -#define BIO_VMERGE_BOUNDARY 0 -#endif - #define BIO_DEBUG #ifdef BIO_DEBUG @@ -235,8 +222,6 @@ static inline void *bio_data(struct bio ((bvec_to_phys((vec1)) + (vec1)->bv_len) == bvec_to_phys((vec2))) #endif -#define BIOVEC_VIRT_MERGEABLE(vec1, vec2) \ - ((((bvec_to_phys((vec1)) + (vec1)->bv_len) | bvec_to_phys((vec2))) & (BIO_VMERGE_BOUNDARY - 1)) == 0) #define __BIO_SEG_BOUNDARY(addr1, addr2, mask) \ (((addr1) | (mask)) == (((addr2) - 1) | (mask))) #define BIOVEC_SEG_BOUNDARY(q, b1, b2) \ Index: linux-2.6.26-devel/fs/bio.c =================================================================== --- linux-2.6.26-devel.orig/fs/bio.c 2008-07-15 23:29:39.000000000 +0200 +++ linux-2.6.26-devel/fs/bio.c 2008-08-08 18:46:30.000000000 +0200 @@ -352,8 +352,7 @@ static int __bio_add_page(struct request */ while (bio->bi_phys_segments >= q->max_phys_segments - || bio->bi_hw_segments >= q->max_hw_segments - || BIOVEC_VIRT_OVERSIZE(bio->bi_size)) { + || bio->bi_hw_segments >= q->max_hw_segments) { if (retried_segments) return 0; @@ -390,8 +389,7 @@ static int __bio_add_page(struct request } /* If we may be able to merge these biovecs, force a recount */ - if (bio->bi_vcnt && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec) || - BIOVEC_VIRT_MERGEABLE(bvec-1, bvec))) + if (bio->bi_vcnt && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec))) bio->bi_flags &= ~(1 << BIO_SEG_VALID); bio->bi_vcnt++; -- 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
