hpfs: implement prefetch to improve performance
This patch implements prefetch to improve performance. It helps mostly when scanning the bitmaps to calculate free space. Signed-off-by: Mikulas Patocka <mpatocka@artax.karlin.mff.cuni.cz> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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a0c1b75963
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275f495dbe
4 changed files with 63 additions and 5 deletions
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@ -7,8 +7,37 @@
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*/
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/blkdev.h>
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#include "hpfs_fn.h"
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void hpfs_prefetch_sectors(struct super_block *s, unsigned secno, int n)
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{
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struct buffer_head *bh;
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struct blk_plug plug;
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if (n <= 0 || unlikely(secno >= hpfs_sb(s)->sb_fs_size))
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return;
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bh = sb_find_get_block(s, secno);
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if (bh) {
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if (buffer_uptodate(bh)) {
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brelse(bh);
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return;
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}
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brelse(bh);
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};
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blk_start_plug(&plug);
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while (n > 0) {
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if (unlikely(secno >= hpfs_sb(s)->sb_fs_size))
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break;
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sb_breadahead(s, secno);
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secno++;
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n--;
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}
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blk_finish_plug(&plug);
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}
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/* Map a sector into a buffer and return pointers to it and to the buffer. */
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void *hpfs_map_sector(struct super_block *s, unsigned secno, struct buffer_head **bhp,
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@ -18,6 +47,8 @@ void *hpfs_map_sector(struct super_block *s, unsigned secno, struct buffer_head
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hpfs_lock_assert(s);
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hpfs_prefetch_sectors(s, secno, ahead);
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cond_resched();
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*bhp = bh = sb_bread(s, secno);
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@ -67,6 +98,8 @@ void *hpfs_map_4sectors(struct super_block *s, unsigned secno, struct quad_buffe
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return NULL;
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}
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hpfs_prefetch_sectors(s, secno, 4 + ahead);
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qbh->data = data = kmalloc(2048, GFP_NOFS);
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if (!data) {
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printk("HPFS: hpfs_map_4sectors: out of memory\n");
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@ -27,8 +27,9 @@
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#define ALLOC_FWD_MAX 128
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#define ALLOC_M 1
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#define FNODE_RD_AHEAD 16
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#define ANODE_RD_AHEAD 16
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#define DNODE_RD_AHEAD 4
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#define ANODE_RD_AHEAD 0
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#define DNODE_RD_AHEAD 72
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#define COUNT_RD_AHEAD 62
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#define FREE_DNODES_ADD 58
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#define FREE_DNODES_DEL 29
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@ -207,6 +208,7 @@ void hpfs_remove_fnode(struct super_block *, fnode_secno fno);
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/* buffer.c */
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void hpfs_prefetch_sectors(struct super_block *, unsigned, int);
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void *hpfs_map_sector(struct super_block *, unsigned, struct buffer_head **, int);
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void *hpfs_get_sector(struct super_block *, unsigned, struct buffer_head **);
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void *hpfs_map_4sectors(struct super_block *, unsigned, struct quad_buffer_head *, int);
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@ -271,6 +273,7 @@ void hpfs_evict_inode(struct inode *);
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__le32 *hpfs_map_dnode_bitmap(struct super_block *, struct quad_buffer_head *);
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__le32 *hpfs_map_bitmap(struct super_block *, unsigned, struct quad_buffer_head *, char *);
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void hpfs_prefetch_bitmap(struct super_block *, unsigned);
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unsigned char *hpfs_load_code_page(struct super_block *, secno);
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__le32 *hpfs_load_bitmap_directory(struct super_block *, secno bmp);
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struct fnode *hpfs_map_fnode(struct super_block *s, ino_t, struct buffer_head **);
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@ -17,6 +17,7 @@ __le32 *hpfs_map_bitmap(struct super_block *s, unsigned bmp_block,
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struct quad_buffer_head *qbh, char *id)
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{
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secno sec;
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__le32 *ret;
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unsigned n_bands = (hpfs_sb(s)->sb_fs_size + 0x3fff) >> 14;
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if (hpfs_sb(s)->sb_chk) if (bmp_block >= n_bands) {
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hpfs_error(s, "hpfs_map_bitmap called with bad parameter: %08x at %s", bmp_block, id);
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@ -27,7 +28,23 @@ __le32 *hpfs_map_bitmap(struct super_block *s, unsigned bmp_block,
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hpfs_error(s, "invalid bitmap block pointer %08x -> %08x at %s", bmp_block, sec, id);
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return NULL;
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}
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return hpfs_map_4sectors(s, sec, qbh, 4);
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ret = hpfs_map_4sectors(s, sec, qbh, 4);
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if (ret) hpfs_prefetch_bitmap(s, bmp_block + 1);
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return ret;
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}
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void hpfs_prefetch_bitmap(struct super_block *s, unsigned bmp_block)
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{
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unsigned to_prefetch, next_prefetch;
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unsigned n_bands = (hpfs_sb(s)->sb_fs_size + 0x3fff) >> 14;
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if (unlikely(bmp_block >= n_bands))
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return;
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to_prefetch = le32_to_cpu(hpfs_sb(s)->sb_bmp_dir[bmp_block]);
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if (unlikely(bmp_block + 1 >= n_bands))
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next_prefetch = 0;
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else
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next_prefetch = le32_to_cpu(hpfs_sb(s)->sb_bmp_dir[bmp_block + 1]);
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hpfs_prefetch_sectors(s, to_prefetch, 4 + 4 * (to_prefetch + 4 == next_prefetch));
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}
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/*
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@ -121,7 +121,7 @@ unsigned hpfs_count_one_bitmap(struct super_block *s, secno secno)
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unsigned long *bits;
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unsigned count;
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bits = hpfs_map_4sectors(s, secno, &qbh, 4);
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bits = hpfs_map_4sectors(s, secno, &qbh, 0);
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if (!bits)
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return 0;
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count = bitmap_weight(bits, 2048 * BITS_PER_BYTE);
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@ -134,8 +134,13 @@ static unsigned count_bitmaps(struct super_block *s)
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unsigned n, count, n_bands;
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n_bands = (hpfs_sb(s)->sb_fs_size + 0x3fff) >> 14;
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count = 0;
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for (n = 0; n < n_bands; n++)
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for (n = 0; n < COUNT_RD_AHEAD; n++) {
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hpfs_prefetch_bitmap(s, n);
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}
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for (n = 0; n < n_bands; n++) {
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hpfs_prefetch_bitmap(s, n + COUNT_RD_AHEAD);
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count += hpfs_count_one_bitmap(s, le32_to_cpu(hpfs_sb(s)->sb_bmp_dir[n]));
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}
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return count;
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}
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