From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58107) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YZ2Q5-0008OR-7A for qemu-devel@nongnu.org; Fri, 20 Mar 2015 15:17:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YZ2Q0-0002XA-Fy for qemu-devel@nongnu.org; Fri, 20 Mar 2015 15:17:21 -0400 From: John Snow Date: Fri, 20 Mar 2015 15:16:50 -0400 Message-Id: <1426879023-18151-8-git-send-email-jsnow@redhat.com> In-Reply-To: <1426879023-18151-1-git-send-email-jsnow@redhat.com> References: <1426879023-18151-1-git-send-email-jsnow@redhat.com> Subject: [Qemu-devel] [PATCH v4 07/20] hbitmap: add hbitmap_merge List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, famz@redhat.com, John Snow , qemu-devel@nongnu.org, armbru@redhat.com, vsementsov@parallels.com, stefanha@redhat.com, mreitz@redhat.com We add a bitmap merge operation to assist in error cases where we wish to combine two bitmaps together. This is algorithmically O(bits) provided HBITMAP_LEVELS remains constant. For a full bitmap on a 64bit machine: sum(bits/64^k, k, 0, HBITMAP_LEVELS) ~= 1.01587 * bits We may be able to improve running speed for particularly sparse bitmaps by using iterators, but the running time for dense maps will be worse. We present the simpler solution first, and we can refine it later if needed. Signed-off-by: John Snow Reviewed-by: Max Reitz --- include/qemu/hbitmap.h | 11 +++++++++++ util/hbitmap.c | 29 +++++++++++++++++++++++++++++ 2 files changed, 40 insertions(+) diff --git a/include/qemu/hbitmap.h b/include/qemu/hbitmap.h index 550d7ce..c19c1cb 100644 --- a/include/qemu/hbitmap.h +++ b/include/qemu/hbitmap.h @@ -65,6 +65,17 @@ struct HBitmapIter { HBitmap *hbitmap_alloc(uint64_t size, int granularity); /** + * hbitmap_merge: + * @a: The bitmap to store the result in. + * @b: The bitmap to merge into @a. + * + * Merge two bitmaps together. + * A := A (BITOR) B. + * B is left unmodified. + */ +bool hbitmap_merge(HBitmap *a, const HBitmap *b); + +/** * hbitmap_empty: * @hb: HBitmap to operate on. * diff --git a/util/hbitmap.c b/util/hbitmap.c index 5b78613..ba11fd3 100644 --- a/util/hbitmap.c +++ b/util/hbitmap.c @@ -399,3 +399,32 @@ HBitmap *hbitmap_alloc(uint64_t size, int granularity) hb->levels[0][0] |= 1UL << (BITS_PER_LONG - 1); return hb; } + +/** + * Given HBitmaps A and B, let A := A (BITOR) B. + * Bitmap B will not be modified. + */ +bool hbitmap_merge(HBitmap *a, const HBitmap *b) +{ + int i, j; + + if ((a->size != b->size) || (a->granularity != b->granularity)) { + return false; + } + + if (hbitmap_count(b) == 0) { + return true; + } + + /* This merge is O(size), as BITS_PER_LONG and HBITMAP_LEVELS are constant. + * It may be possible to improve running times for sparsely populated maps + * by using hbitmap_iter_next, but this is suboptimal for dense maps. + */ + for (i = HBITMAP_LEVELS - 1; i >= 0; i--) { + for (j = 0; j < a->sizes[i]; j++) { + a->levels[i][j] |= b->levels[i][j]; + } + } + + return true; +} -- 2.1.0