1 /* 2 * Multifd zero page detection implementation. 3 * 4 * Copyright (c) 2024 Bytedance Inc 5 * 6 * Authors: 7 * Hao Xiang <hao.xiang@bytedance.com> 8 * 9 * This work is licensed under the terms of the GNU GPL, version 2 or later. 10 * See the COPYING file in the top-level directory. 11 */ 12 13 #include "qemu/osdep.h" 14 #include "qemu/cutils.h" 15 #include "exec/ramblock.h" 16 #include "migration.h" 17 #include "multifd.h" 18 #include "options.h" 19 #include "ram.h" 20 21 static bool multifd_zero_page_enabled(void) 22 { 23 return migrate_zero_page_detection() == ZERO_PAGE_DETECTION_MULTIFD; 24 } 25 26 static void swap_page_offset(ram_addr_t *pages_offset, int a, int b) 27 { 28 ram_addr_t temp; 29 30 if (a == b) { 31 return; 32 } 33 34 temp = pages_offset[a]; 35 pages_offset[a] = pages_offset[b]; 36 pages_offset[b] = temp; 37 } 38 39 /** 40 * multifd_send_zero_page_detect: Perform zero page detection on all pages. 41 * 42 * Sorts normal pages before zero pages in p->pages->offset and updates 43 * p->pages->normal_num. 44 * 45 * @param p A pointer to the send params. 46 */ 47 void multifd_send_zero_page_detect(MultiFDSendParams *p) 48 { 49 MultiFDPages_t *pages = p->pages; 50 RAMBlock *rb = pages->block; 51 int i = 0; 52 int j = pages->num - 1; 53 54 if (!multifd_zero_page_enabled()) { 55 pages->normal_num = pages->num; 56 return; 57 } 58 59 /* 60 * Sort the page offset array by moving all normal pages to 61 * the left and all zero pages to the right of the array. 62 */ 63 while (i <= j) { 64 uint64_t offset = pages->offset[i]; 65 66 if (!buffer_is_zero(rb->host + offset, p->page_size)) { 67 i++; 68 continue; 69 } 70 71 swap_page_offset(pages->offset, i, j); 72 ram_release_page(rb->idstr, offset); 73 j--; 74 } 75 76 pages->normal_num = i; 77 } 78 79 void multifd_recv_zero_page_process(MultiFDRecvParams *p) 80 { 81 for (int i = 0; i < p->zero_num; i++) { 82 void *page = p->host + p->zero[i]; 83 if (!buffer_is_zero(page, p->page_size)) { 84 memset(page, 0, p->page_size); 85 } 86 } 87 } 88