From 3edcd7e6ebae3ef0ac178eed5f4225803159562d Mon Sep 17 00:00:00 2001 From: Peter Lieven Date: Tue, 26 Mar 2013 10:58:35 +0100 Subject: [PATCH] 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: Peter Lieven Reviewed-by: Orit Wasserman Reviewed-by: Eric Blake Signed-off-by: Juan Quintela --- arch_init.c | 21 ++++++--------------- 1 file changed, 6 insertions(+), 15 deletions(-) diff --git a/arch_init.c b/arch_init.c index 35974c282..dd5deffa9 100644 --- a/arch_init.c +++ b/arch_init.c @@ -146,19 +146,10 @@ int qemu_read_default_config_files(bool userconfig) return 0; } -static int is_dup_page(uint8_t *page) +static inline bool is_zero_page(uint8_t *p) { - VECTYPE *p = (VECTYPE *)page; - VECTYPE val = SPLAT(page); - int i; - - for (i = 0; i < TARGET_PAGE_SIZE / sizeof(VECTYPE); i++) { - if (!ALL_EQ(val, p[i])) { - return 0; - } - } - - return 1; + return buffer_find_nonzero_offset(p, TARGET_PAGE_SIZE) == + TARGET_PAGE_SIZE; } /* struct contains XBZRLE cache and a static page @@ -445,12 +436,12 @@ static int ram_save_block(QEMUFile *f, bool last_stage) /* In doubt sent page as normal */ bytes_sent = -1; - if (is_dup_page(p)) { + if (is_zero_page(p)) { acct_info.dup_pages++; bytes_sent = save_block_hdr(f, block, offset, cont, RAM_SAVE_FLAG_COMPRESS); - qemu_put_byte(f, *p); - bytes_sent += 1; + qemu_put_byte(f, 0); + bytes_sent++; } else if (migrate_use_xbzrle()) { current_addr = block->offset + offset; bytes_sent = save_xbzrle_page(f, p, current_addr, block, -- 2.39.2