Commit 07ac4cdb authored by Fam Zheng's avatar Fam Zheng Committed by Max Reitz
Browse files

HBitmap: Introduce "meta" bitmap to track bit changes 



Upon each bit toggle, the corresponding bit in the meta bitmap will be
set.

Signed-off-by: default avatarFam Zheng <famz@redhat.com>
[Amended text inline. --js]
Reviewed-by: default avatarMax Reitz <mreitz@redhat.com>

Signed-off-by: default avatarJohn Snow <jsnow@redhat.com>
Message-id: 1476395910-8697-3-git-send-email-jsnow@redhat.com
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
parent dc162c8e

include/qemu/hbitmap.h

+21 −0
Original line number Diff line number Diff line
@@ -178,6 +178,27 @@ void hbitmap_iter_init(HBitmapIter *hbi, const HBitmap *hb, uint64_t first); 
 */

unsigned long hbitmap_iter_skip_words(HBitmapIter *hbi);



/* hbitmap_create_meta:

 * Create a "meta" hbitmap to track dirtiness of the bits in this HBitmap.

 * The caller owns the created bitmap and must call hbitmap_free_meta(hb) to

 * free it.

 *

 * Currently, we only guarantee that if a bit in the hbitmap is changed it

 * will be reflected in the meta bitmap, but we do not yet guarantee the

 * opposite.

 *

 * @hb: The HBitmap to operate on.

 * @chunk_size: How many bits in @hb does one bit in the meta track.

 */

HBitmap *hbitmap_create_meta(HBitmap *hb, int chunk_size);



/* hbitmap_free_meta:

 * Free the meta bitmap of @hb.

 *

 * @hb: The HBitmap whose meta bitmap should be freed.

 */

void hbitmap_free_meta(HBitmap *hb);



/**

 * hbitmap_iter_next:

 * @hbi: HBitmapIter to operate on.

util/hbitmap.c

+54 −15
Original line number Diff line number Diff line
@@ -78,6 +78,9 @@ struct HBitmap { 
     */

    int granularity;



    /* A meta dirty bitmap to track the dirtiness of bits in this HBitmap. */

    HBitmap *meta;



    /* A number of progressively less coarse bitmaps (i.e. level 0 is the

     * coarsest).  Each bit in level N represents a word in level N+1 that

     * has a set bit, except the last level where each bit represents the
@@ -209,25 +212,27 @@ static uint64_t hb_count_between(HBitmap *hb, uint64_t start, uint64_t last) 
}



/* Setting starts at the last layer and propagates up if an element

 * changes from zero to non-zero.

 * changes.

 */

static inline bool hb_set_elem(unsigned long *elem, uint64_t start, uint64_t last)

{

    unsigned long mask;

    bool changed;

    unsigned long old;



    assert((last >> BITS_PER_LEVEL) == (start >> BITS_PER_LEVEL));

    assert(start <= last);



    mask = 2UL << (last & (BITS_PER_LONG - 1));

    mask -= 1UL << (start & (BITS_PER_LONG - 1));

    changed = (*elem == 0);

    old = *elem;

    *elem |= mask;

    return changed;

    return old != *elem;

}



/* The recursive workhorse (the depth is limited to HBITMAP_LEVELS)... */

static void hb_set_between(HBitmap *hb, int level, uint64_t start, uint64_t last)

/* The recursive workhorse (the depth is limited to HBITMAP_LEVELS)...

 * Returns true if at least one bit is changed. */

static bool hb_set_between(HBitmap *hb, int level, uint64_t start,

                           uint64_t last)

{

    size_t pos = start >> BITS_PER_LEVEL;

    size_t lastpos = last >> BITS_PER_LEVEL;
@@ -256,23 +261,28 @@ static void hb_set_between(HBitmap *hb, int level, uint64_t start, uint64_t last 
    if (level > 0 && changed) {

        hb_set_between(hb, level - 1, pos, lastpos);

    }

    return changed;

}



void hbitmap_set(HBitmap *hb, uint64_t start, uint64_t count)

{

    /* Compute range in the last layer.  */

    uint64_t first, n;

    uint64_t last = start + count - 1;



    trace_hbitmap_set(hb, start, count,

                      start >> hb->granularity, last >> hb->granularity);



    start >>= hb->granularity;

    first = start >> hb->granularity;

    last >>= hb->granularity;

    count = last - start + 1;

    assert(last < hb->size);

    n = last - first + 1;



    hb->count += count - hb_count_between(hb, start, last);

    hb_set_between(hb, HBITMAP_LEVELS - 1, start, last);

    hb->count += n - hb_count_between(hb, first, last);

    if (hb_set_between(hb, HBITMAP_LEVELS - 1, first, last) &&

        hb->meta) {

        hbitmap_set(hb->meta, start, count);

    }

}



/* Resetting works the other way round: propagate up if the new
@@ -293,8 +303,10 @@ static inline bool hb_reset_elem(unsigned long *elem, uint64_t start, uint64_t l 
    return blanked;

}



/* The recursive workhorse (the depth is limited to HBITMAP_LEVELS)... */

static void hb_reset_between(HBitmap *hb, int level, uint64_t start, uint64_t last)

/* The recursive workhorse (the depth is limited to HBITMAP_LEVELS)...

 * Returns true if at least one bit is changed. */

static bool hb_reset_between(HBitmap *hb, int level, uint64_t start,

                             uint64_t last)

{

    size_t pos = start >> BITS_PER_LEVEL;

    size_t lastpos = last >> BITS_PER_LEVEL;
@@ -337,22 +349,29 @@ static void hb_reset_between(HBitmap *hb, int level, uint64_t start, uint64_t la 
    if (level > 0 && changed) {

        hb_reset_between(hb, level - 1, pos, lastpos);

    }



    return changed;



}



void hbitmap_reset(HBitmap *hb, uint64_t start, uint64_t count)

{

    /* Compute range in the last layer.  */

    uint64_t first;

    uint64_t last = start + count - 1;



    trace_hbitmap_reset(hb, start, count,

                        start >> hb->granularity, last >> hb->granularity);



    start >>= hb->granularity;

    first = start >> hb->granularity;

    last >>= hb->granularity;

    assert(last < hb->size);



    hb->count -= hb_count_between(hb, start, last);

    hb_reset_between(hb, HBITMAP_LEVELS - 1, start, last);

    hb->count -= hb_count_between(hb, first, last);

    if (hb_reset_between(hb, HBITMAP_LEVELS - 1, first, last) &&

        hb->meta) {

        hbitmap_set(hb->meta, start, count);

    }

}



void hbitmap_reset_all(HBitmap *hb)
@@ -381,6 +400,7 @@ bool hbitmap_get(const HBitmap *hb, uint64_t item) 
void hbitmap_free(HBitmap *hb)

{

    unsigned i;

    assert(!hb->meta);

    for (i = HBITMAP_LEVELS; i-- > 0; ) {

        g_free(hb->levels[i]);

    }
@@ -458,6 +478,9 @@ void hbitmap_truncate(HBitmap *hb, uint64_t size) 
                   (size - old) * sizeof(*hb->levels[i]));

        }

    }

    if (hb->meta) {

        hbitmap_truncate(hb->meta, hb->size << hb->granularity);

    }

}
@@ -493,3 +516,19 @@ bool hbitmap_merge(HBitmap *a, const HBitmap *b) 


    return true;

}



HBitmap *hbitmap_create_meta(HBitmap *hb, int chunk_size)

{

    assert(!(chunk_size & (chunk_size - 1)));

    assert(!hb->meta);

    hb->meta = hbitmap_alloc(hb->size << hb->granularity,

                             hb->granularity + ctz32(chunk_size));

    return hb->meta;

}



void hbitmap_free_meta(HBitmap *hb)

{

    assert(hb->meta);

    hbitmap_free(hb->meta);

    hb->meta = NULL;

}