Commit 3edcd7e6 authored by Peter Lieven's avatar Peter Lieven Committed by Juan Quintela

migration: search for zero instead of dup pages

virtually all dup pages are zero pages. remove
the special is_dup_page() function and use the
optimized buffer_find_nonzero_offset() function
instead.

here buffer_find_nonzero_offset() is used directly
to avoid the unnecssary additional checks in
buffer_is_zero().

raw performace gain checking 1 GByte zeroed memory
over is_dup_page() is approx. 10-12% with SSE2
and 8-10% with unsigned long arithmedtic.
Signed-off-by: default avatarPeter Lieven <pl@kamp.de>
Reviewed-by: default avatarOrit Wasserman <owasserm@redhat.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Signed-off-by: default avatarJuan Quintela <quintela@redhat.com>
parent 49f676a0
...@@ -146,19 +146,10 @@ int qemu_read_default_config_files(bool userconfig) ...@@ -146,19 +146,10 @@ int qemu_read_default_config_files(bool userconfig)
return 0; return 0;
} }
static int is_dup_page(uint8_t *page) static inline bool is_zero_page(uint8_t *p)
{ {
VECTYPE *p = (VECTYPE *)page; return buffer_find_nonzero_offset(p, TARGET_PAGE_SIZE) ==
VECTYPE val = SPLAT(page); TARGET_PAGE_SIZE;
int i;
for (i = 0; i < TARGET_PAGE_SIZE / sizeof(VECTYPE); i++) {
if (!ALL_EQ(val, p[i])) {
return 0;
}
}
return 1;
} }
/* struct contains XBZRLE cache and a static page /* struct contains XBZRLE cache and a static page
...@@ -445,12 +436,12 @@ static int ram_save_block(QEMUFile *f, bool last_stage) ...@@ -445,12 +436,12 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
/* In doubt sent page as normal */ /* In doubt sent page as normal */
bytes_sent = -1; bytes_sent = -1;
if (is_dup_page(p)) { if (is_zero_page(p)) {
acct_info.dup_pages++; acct_info.dup_pages++;
bytes_sent = save_block_hdr(f, block, offset, cont, bytes_sent = save_block_hdr(f, block, offset, cont,
RAM_SAVE_FLAG_COMPRESS); RAM_SAVE_FLAG_COMPRESS);
qemu_put_byte(f, *p); qemu_put_byte(f, 0);
bytes_sent += 1; bytes_sent++;
} else if (migrate_use_xbzrle()) { } else if (migrate_use_xbzrle()) {
current_addr = block->offset + offset; current_addr = block->offset + offset;
bytes_sent = save_xbzrle_page(f, p, current_addr, block, bytes_sent = save_xbzrle_page(f, p, current_addr, block,
......
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