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bh=EUjd+KKO1a0SIehqfLmmOxI1GH8hjBJlH4OWswskEH8=; b=Na42/nziHYOau5dLtU4U1YahrBBmjKbU6XbybaVU7soxco5amQkmOTgUPqpayNeNyEj8mW ixMfytWJFo6YXUrnBud8Yz5D9oVnuD9o27wvQSVuGKopBfl6QuTs295Adz6e3eBZQeVZc0 TpHM/jWPesVceO1nFvAu8ksbFPRcDa0= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1701116799; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EUjd+KKO1a0SIehqfLmmOxI1GH8hjBJlH4OWswskEH8=; b=fQBPVpkru1rRKuDGTuxmINvJeoAlWYLiWecXr9+9iuavxBPN1uK+HSc3LBn7cVHMvKf6sF 9/18XuszpgQNr5DA== From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: berrange@redhat.com, armbru@redhat.com, Juan Quintela , Peter Xu , Leonardo Bras , Claudio Fontana , Nikolay Borisov , Paolo Bonzini , David Hildenbrand , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Subject: [RFC PATCH v3 08/30] migration/ram: Add outgoing 'fixed-ram' migration Date: Mon, 27 Nov 2023 17:25:50 -0300 Message-Id: <20231127202612.23012-9-farosas@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20231127202612.23012-1-farosas@suse.de> References: <20231127202612.23012-1-farosas@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Authentication-Results: smtp-out1.suse.de; 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charset="utf-8" From: Nikolay Borisov Implement the outgoing migration side for the 'fixed-ram' capability. A bitmap is introduced to track which pages have been written in the migration file. Pages are written at a fixed location for every ramblock. Zero pages are ignored as they'd be zero in the destination migration as well. The migration stream is altered to put the dirty pages for a ramblock after its header instead of having a sequential stream of pages that follow the ramblock headers. Since all pages have a fixed location, RAM_SAVE_FLAG_EOS is no longer generated on every migration iteration. Without fixed-ram (current): With fixed-ram (new): --------------------- -------------------------------- | ramblock 1 header | | ramblock 1 header | --------------------- -------------------------------- | ramblock 2 header | | ramblock 1 fixed-ram header | --------------------- -------------------------------- | ... | | padding to next 1MB boundary | --------------------- | ... | | ramblock n header | -------------------------------- --------------------- | ramblock 1 pages | | RAM_SAVE_FLAG_EOS | | ... | --------------------- -------------------------------- | stream of pages | | ramblock 2 header | | (iter 1) | -------------------------------- | ... | | ramblock 2 fixed-ram header | --------------------- -------------------------------- | RAM_SAVE_FLAG_EOS | | padding to next 1MB boundary | --------------------- | ... | | stream of pages | -------------------------------- | (iter 2) | | ramblock 2 pages | | ... | | ... | --------------------- -------------------------------- | ... | | ... | --------------------- -------------------------------- | RAM_SAVE_FLAG_EOS | -------------------------------- | ... | -------------------------------- where: - ramblock header: the generic information for a ramblock, such as idstr, used_len, etc. - ramblock fixed-ram header: the new information added by this feature: bitmap of pages written, bitmap size and offset of pages in the migration file. Signed-off-by: Nikolay Borisov Signed-off-by: Fabiano Rosas --- - used a macro for alignment value - documented alignment assumptions - moved shadow_bmap debug code to multifd patch - did NOT use used_length for bmap, it breaks dirty page tracking somehow - uncommented the capability enabling - accounted for the bitmap size with ram_transferred_add() --- include/exec/ramblock.h | 8 +++ migration/ram.c | 121 +++++++++++++++++++++++++++++++++++++--- 2 files changed, 120 insertions(+), 9 deletions(-) diff --git a/include/exec/ramblock.h b/include/exec/ramblock.h index 69c6a53902..e0e3f16852 100644 --- a/include/exec/ramblock.h +++ b/include/exec/ramblock.h @@ -44,6 +44,14 @@ struct RAMBlock { size_t page_size; /* dirty bitmap used during migration */ unsigned long *bmap; + /* shadow dirty bitmap used when migrating to a file */ + unsigned long *shadow_bmap; + /* + * offset in the file pages belonging to this ramblock are saved, + * used only during migration to a file. + */ + off_t bitmap_offset; + uint64_t pages_offset; /* bitmap of already received pages in postcopy */ unsigned long *receivedmap; =20 diff --git a/migration/ram.c b/migration/ram.c index 8c7886ab79..4a0ab8105f 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -94,6 +94,18 @@ #define RAM_SAVE_FLAG_MULTIFD_FLUSH 0x200 /* We can't use any flag that is bigger than 0x200 */ =20 +/* + * fixed-ram migration supports O_DIRECT, so we need to make sure the + * userspace buffer, the IO operation size and the file offset are + * aligned according to the underlying device's block size. The first + * two are already aligned to page size, but we need to add padding to + * the file to align the offset. We cannot read the block size + * dynamically because the migration file can be moved between + * different systems, so use 1M to cover most block sizes and to keep + * the file offset aligned at page size as well. + */ +#define FIXED_RAM_FILE_OFFSET_ALIGNMENT 0x100000 + XBZRLECacheStats xbzrle_counters; =20 /* used by the search for pages to send */ @@ -1127,12 +1139,18 @@ static int save_zero_page(RAMState *rs, PageSearchS= tatus *pss, return 0; } =20 + stat64_add(&mig_stats.zero_pages, 1); + + if (migrate_fixed_ram()) { + /* zero pages are not transferred with fixed-ram */ + clear_bit(offset >> TARGET_PAGE_BITS, pss->block->shadow_bmap); + return 1; + } + len +=3D save_page_header(pss, file, pss->block, offset | RAM_SAVE_FLA= G_ZERO); qemu_put_byte(file, 0); len +=3D 1; ram_release_page(pss->block->idstr, offset); - - stat64_add(&mig_stats.zero_pages, 1); ram_transferred_add(len); =20 /* @@ -1190,14 +1208,20 @@ static int save_normal_page(PageSearchStatus *pss, = RAMBlock *block, { QEMUFile *file =3D pss->pss_channel; =20 - ram_transferred_add(save_page_header(pss, pss->pss_channel, block, - offset | RAM_SAVE_FLAG_PAGE)); - if (async) { - qemu_put_buffer_async(file, buf, TARGET_PAGE_SIZE, - migrate_release_ram() && - migration_in_postcopy()); + if (migrate_fixed_ram()) { + qemu_put_buffer_at(file, buf, TARGET_PAGE_SIZE, + block->pages_offset + offset); + set_bit(offset >> TARGET_PAGE_BITS, block->shadow_bmap); } else { - qemu_put_buffer(file, buf, TARGET_PAGE_SIZE); + ram_transferred_add(save_page_header(pss, pss->pss_channel, block, + offset | RAM_SAVE_FLAG_PAGE)); + if (async) { + qemu_put_buffer_async(file, buf, TARGET_PAGE_SIZE, + migrate_release_ram() && + migration_in_postcopy()); + } else { + qemu_put_buffer(file, buf, TARGET_PAGE_SIZE); + } } ram_transferred_add(TARGET_PAGE_SIZE); stat64_add(&mig_stats.normal_pages, 1); @@ -2413,6 +2437,8 @@ static void ram_save_cleanup(void *opaque) block->clear_bmap =3D NULL; g_free(block->bmap); block->bmap =3D NULL; + g_free(block->shadow_bmap); + block->shadow_bmap =3D NULL; } =20 xbzrle_cleanup(); @@ -2780,6 +2806,7 @@ static void ram_list_init_bitmaps(void) */ block->bmap =3D bitmap_new(pages); bitmap_set(block->bmap, 0, pages); + block->shadow_bmap =3D bitmap_new(pages); block->clear_bmap_shift =3D shift; block->clear_bmap =3D bitmap_new(clear_bmap_size(pages, shift)= ); } @@ -2917,6 +2944,58 @@ void qemu_guest_free_page_hint(void *addr, size_t le= n) } } =20 +#define FIXED_RAM_HDR_VERSION 1 +struct FixedRamHeader { + uint32_t version; + /* + * The target's page size, so we know how many pages are in the + * bitmap. + */ + uint64_t page_size; + /* + * The offset in the migration file where the pages bitmap is + * found. + */ + uint64_t bitmap_offset; + /* + * The offset in the migration file where the actual pages (data) + * are found. + */ + uint64_t pages_offset; + /* end of v1 */ +} QEMU_PACKED; +typedef struct FixedRamHeader FixedRamHeader; + +static void fixed_ram_insert_header(QEMUFile *file, RAMBlock *block) +{ + g_autofree FixedRamHeader *header; + size_t header_size, bitmap_size; + long num_pages; + + header =3D g_new0(FixedRamHeader, 1); + header_size =3D sizeof(FixedRamHeader); + + num_pages =3D block->used_length >> TARGET_PAGE_BITS; + bitmap_size =3D BITS_TO_LONGS(num_pages) * sizeof(unsigned long); + + /* + * Save the file offsets of where the bitmap and the pages should + * go as they are written at the end of migration and during the + * iterative phase, respectively. + */ + block->bitmap_offset =3D qemu_get_offset(file) + header_size; + block->pages_offset =3D ROUND_UP(block->bitmap_offset + + bitmap_size, + FIXED_RAM_FILE_OFFSET_ALIGNMENT); + + header->version =3D cpu_to_be32(FIXED_RAM_HDR_VERSION); + header->page_size =3D cpu_to_be64(TARGET_PAGE_SIZE); + header->bitmap_offset =3D cpu_to_be64(block->bitmap_offset); + header->pages_offset =3D cpu_to_be64(block->pages_offset); + + qemu_put_buffer(file, (uint8_t *) header, header_size); +} + /* * Each of ram_save_setup, ram_save_iterate and ram_save_complete has * long-running RCU critical section. When rcu-reclaims in the code @@ -2966,6 +3045,13 @@ static int ram_save_setup(QEMUFile *f, void *opaque) if (migrate_ignore_shared()) { qemu_put_be64(f, block->mr->addr); } + + if (migrate_fixed_ram()) { + fixed_ram_insert_header(f, block); + /* prepare offset for next ramblock */ + qemu_set_offset(f, block->pages_offset + block->used_lengt= h, + SEEK_SET); + } } } =20 @@ -2999,6 +3085,19 @@ static int ram_save_setup(QEMUFile *f, void *opaque) return qemu_fflush(f); } =20 +static void ram_save_shadow_bmap(QEMUFile *f) +{ + RAMBlock *block; + + RAMBLOCK_FOREACH_MIGRATABLE(block) { + long num_pages =3D block->used_length >> TARGET_PAGE_BITS; + long bitmap_size =3D BITS_TO_LONGS(num_pages) * sizeof(unsigned lo= ng); + qemu_put_buffer_at(f, (uint8_t *)block->shadow_bmap, bitmap_size, + block->bitmap_offset); + ram_transferred_add(bitmap_size); + } +} + /** * ram_save_iterate: iterative stage for migration * @@ -3188,6 +3287,10 @@ static int ram_save_complete(QEMUFile *f, void *opaq= ue) return ret; } =20 + if (migrate_fixed_ram()) { + ram_save_shadow_bmap(f); + } + if (migrate_multifd() && !migrate_multifd_flush_after_each_section()) { qemu_put_be64(f, RAM_SAVE_FLAG_MULTIFD_FLUSH); } --=20 2.35.3