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qcow2: reuse cluster data for adjacent sectors (speed up ~30%)

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This commit is contained in:
Ivan Baravy 2023-01-18 20:16:33 +00:00
parent dd34949209
commit 65cbfbc743
1 changed files with 19 additions and 12 deletions
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31
vdisk/qcow2.c
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@ -37,6 +37,7 @@ struct vdisk_qcow2 {
size_t l1_size;
uint64_t sector_idx_mask;
uint64_t *l1;
uint64_t prev_cluster_index;
};
#define QCOW2_MAGIC "QFI\xfb"
@ -100,6 +101,14 @@ qcow2_read_guest_sector(struct vdisk_qcow2 *d, uint64_t sector, uint8_t *buf) {
uint64_t l1_entry = d->l1[l1_index];
uint64_t l2_entry;
if (cluster_index == d->prev_cluster_index) {
memcpy(buf,
d->cluster + (sector & d->sector_idx_mask) * d->vdisk.sect_size,
d->vdisk.sect_size);
return;
}
d->prev_cluster_index = cluster_index;
uint64_t l2_table_offset = l1_entry & L1_ENTRY_OFFSET_MASK;
if (!l2_table_offset) {
memset(buf, 0, d->vdisk.sect_size);
@ -126,9 +135,6 @@ qcow2_read_guest_sector(struct vdisk_qcow2 *d, uint64_t sector, uint8_t *buf) {
strerror(errno));
return;
}
memcpy(buf,
d->cluster + (sector & d->sector_idx_mask) * d->vdisk.sect_size,
d->vdisk.sect_size);
} else {
off_t cmp_offset = d->l2_entry_cmp_offset_mask & l2_entry;
printf("cmp_offset: 0x%" PRIx64 "\n", cmp_offset);
@ -143,10 +149,10 @@ qcow2_read_guest_sector(struct vdisk_qcow2 *d, uint64_t sector, uint8_t *buf) {
}
unsigned long dest_size = d->cluster_size;
uncompress(d->cluster, &dest_size, d->cmp_cluster, cmp_size);
memcpy(buf,
d->cluster + (sector & d->sector_idx_mask) * d->vdisk.sect_size,
d->vdisk.sect_size);
}
memcpy(buf,
d->cluster + (sector & d->sector_idx_mask) * d->vdisk.sect_size,
d->vdisk.sect_size);
}
STDCALL void
@ -194,18 +200,19 @@ struct vdisk*
vdisk_init_qcow2(const char *fname, struct umka_io *io) {
struct vdisk_qcow2 *d =
(struct vdisk_qcow2*)calloc(1, sizeof(struct vdisk_qcow2));
d->vdisk.diskfunc = (diskfunc_t) {.strucsize = sizeof(diskfunc_t),
.close = vdisk_qcow2_close,
.read = vdisk_qcow2_read,
.write = vdisk_qcow2_write,
};
d->vdisk.io = io;
if (!d) {
fprintf(stderr, "[vdisk.qcow2] can't allocate memory: %s\n",
strerror(errno));
return NULL;
}
d->vdisk.diskfunc = (diskfunc_t) {.strucsize = sizeof(diskfunc_t),
.close = vdisk_qcow2_close,
.read = vdisk_qcow2_read,
.write = vdisk_qcow2_write,
};
d->vdisk.io = io;
d->prev_cluster_index = ~(uint64_t)0;
if (!(d->fd = open(fname, O_RDONLY))) {
fprintf(stderr, "[vdisk.qcow2] can't open file '%s': %s\n", fname,
strerror(errno));