On 02/11/2010 Anthony Liguori <anthony@xxxxxxxxxxxxx> wrote:
> Oh, I see what's happening here. Yes, I think a leul_to_cpu() makes more
> sense.
Maybe I'm missing something here.
I couldn't find leul_to_cpu(), so have defined it in bswap.h.
Correct?
--- a/bswap.h
+++ b/bswap.h
@@ -205,8 +205,10 @@ static inline void cpu_to_be32wu(uint32_t *p, uint32_t v)
#ifdef HOST_WORDS_BIGENDIAN
#define cpu_to_32wu cpu_to_be32wu
+#define leul_to_cpu(v) le ## HOST_LONG_BITS ## _to_cpu(v)
#else
#define cpu_to_32wu cpu_to_le32wu
+#define leul_to_cpu(v) (v)
#endif
On 02/10/2010 Ulrich Drepper <drepper@xxxxxxxxxx> wrote:
> If you're optimizing this code you might want to do it all. The
> compiler might not see through the bswap call and create unnecessary
> data dependencies. Especially problematic if the bitmap is really
> sparse. Also, the outer test is != while the inner test is >. Be
> consistent. I suggest to replace the inner loop with
>
> do {
> ...
> } while (c != 0);
>
> Depending on how sparse the bitmap is populated this might reduce the
> number of data dependencies quite a bit.
Combining all comments, the code would be like this.
if (bitmap_ul[i] != 0) {
c = leul_to_cpu(bitmap_ul[i]);
do {
j = ffsl(c) - 1;
c &= ~(1ul << j);
page_number = i * HOST_LONG_BITS + j;
addr1 = page_number * TARGET_PAGE_SIZE;
addr = offset + addr1;
ram_addr = cpu_get_physical_page_desc(addr);
cpu_physical_memory_set_dirty(ram_addr);
} while (c != 0);
}
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