At 03/03/2011 06:27 AM, Stefan Weil Write: > Am 02.03.2011 23:01, schrieb Stefan Weil: >> Am 02.03.2011 19:47, schrieb Peter Maydell: >>> On 2 March 2011 18:36, Stefan Weil <w...@mail.berlios.de> wrote: >>>> No. I dont't think that the third parameter of bitmap_clear is >>>> ok like that. See my patch for the correct value. >>> >>> Wen's patch: >>> >>> + const size_t width = ds_get_width(vd->ds) / 16; >>> [...] >>> - bitmap_set(width_mask, 0, (ds_get_width(vd->ds) / 16)); >>> - bitmap_clear(width_mask, (ds_get_width(vd->ds) / 16), >>> - VNC_DIRTY_WORDS * BITS_PER_LONG); >>> + bitmap_set(width_mask, 0, width); >>> + bitmap_clear(width_mask, width, VNC_DIRTY_WORDS * BITS_PER_LONG >>> - width); >>> >>> Your patch: >>> >>> bitmap_clear(width_mask, (ds_get_width(vd->ds) / 16), >>> - VNC_DIRTY_WORDS * BITS_PER_LONG); >>> + (VNC_MAX_WIDTH - ds_get_width(vd->ds)) / 16); >>> >>> Since ui/vnc.h has: >>> >>> #define VNC_DIRTY_WORDS (VNC_MAX_WIDTH / (16 * BITS_PER_LONG)) >>> >>> the third parameter to bitmap_clear is the same value in >>> both cases, isn't it? Or is this a rounding bug? >>> >>> -- PMM >> >> Because of rounding effects, both values can be different. >> >> The part missing in my patch is correct handling of another >> rounding effect: >> >> VNC_DIRTY_WORDS is exact for 32 bit long values (and the >> "old" code which used uint32_t until some weeks ago), where >> VNC_DIRTY_WORDS = 2560/16/32 = 5. >> >> For 64 bit values, VNC_DIRTY_WORDS = 2560/16/64 = 2 (rounded)! >> >> Stefan W. > > > Is bitmap_clear() really needed here? Meanwhile I think it is not, > so this might be a new patch variant...
I do not know why we call bitmap_clear() hear. I only know it is the same as the old code: -static inline void vnc_set_bits(uint32_t *d, int n, int nb_words) -{ - int j; - - j = 0; - while (n >= 32) { - d[j++] = -1; - n -= 32; - } - if (n > 0) - d[j++] = (1 << n) - 1; - while (j < nb_words) <=== bitmap_clear() - d[j++] = 0; -} - vnc_set_bits(width_mask, (ds_get_width(vd->ds) / 16), VNC_DIRTY_WORDS); + bitmap_set(width_mask, 0, (ds_get_width(vd->ds) / 16)); + bitmap_clear(width_mask, (ds_get_width(vd->ds) / 16), + VNC_DIRTY_WORDS * BITS_PER_LONG); > > >