From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 09E89C4332F for ; Tue, 31 Oct 2023 17:34:23 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qxsc9-0007QG-L3; Tue, 31 Oct 2023 13:33:17 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qxsc3-0007Mq-D5 for qemu-devel@nongnu.org; Tue, 31 Oct 2023 13:33:11 -0400 Received: from smtp-out1.suse.de ([2001:67c:2178:6::1c]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1qxsc1-0007T4-2V for qemu-devel@nongnu.org; Tue, 31 Oct 2023 13:33:11 -0400 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 8EA5221860; Tue, 31 Oct 2023 17:33:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1698773587; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Cvll5GTO4AbGGAbEz9bmtDak+3k2PB8nFuOFhphtn2I=; b=T+00n6JUCyaWZ6V2FDqh0b5Py1JI4yPdNy3A05J+YNKsDwN6a1qD8hbqyNJGW3TSm+8CYq DTn0ArnfRtO4DEEi8Oixcj9p0CIguCVt64Pz3+tS3zxx6z2I1nUoNaDgtNZDidO12biFT5 uwlNMh9tbfeDy+xzFrNt78jc5gnMRak= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1698773587; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Cvll5GTO4AbGGAbEz9bmtDak+3k2PB8nFuOFhphtn2I=; b=O7y79zVcNCjjaxYwuUEiEx0/e0YBbHgaR5l7URR5iKDy4U3nxufZu2FtaFpXsfuEaIMhlD dg6ZdLP9jE9tm2Cg== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 1B89D1391B; Tue, 31 Oct 2023 17:33:06 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id kZIWNlI6QWW4dQAAMHmgww (envelope-from ); Tue, 31 Oct 2023 17:33:06 +0000 From: Fabiano Rosas To: Peter Xu Cc: qemu-devel@nongnu.org, berrange@redhat.com, armbru@redhat.com, Juan Quintela , Leonardo Bras , Claudio Fontana , Nikolay Borisov , Paolo Bonzini , David Hildenbrand , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH v2 15/29] migration/ram: Add support for 'fixed-ram' outgoing migration In-Reply-To: References: <20231023203608.26370-1-farosas@suse.de> <20231023203608.26370-16-farosas@suse.de> Date: Tue, 31 Oct 2023 14:33:04 -0300 Message-ID: <87zfzyd7e7.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: pass client-ip=2001:67c:2178:6::1c; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Peter Xu writes: > On Mon, Oct 23, 2023 at 05:35:54PM -0300, Fabiano Rosas wrote: >> 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): >> >> ramblock 1 header|ramblock 2 header|...|RAM_SAVE_FLAG_EOS|stream of >> pages (iter 1)|RAM_SAVE_FLAG_EOS|stream of pages (iter 2)|... >> >> With fixed-ram (new): >> >> ramblock 1 header|ramblock 1 fixed-ram header|ramblock 1 pages (fixed >> offsets)|ramblock 2 header|ramblock 2 fixed-ram header|ramblock 2 >> pages (fixed offsets)|...|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 >> --- >> include/exec/ramblock.h | 8 ++++ >> migration/options.c | 3 -- >> migration/ram.c | 98 ++++++++++++++++++++++++++++++++++++----- >> 3 files changed, 96 insertions(+), 13 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; >> >> diff --git a/migration/options.c b/migration/options.c >> index 2622d8c483..9f693d909f 100644 >> --- a/migration/options.c >> +++ b/migration/options.c >> @@ -271,12 +271,9 @@ bool migrate_events(void) >> >> bool migrate_fixed_ram(void) >> { >> -/* >> MigrationState *s = migrate_get_current(); >> >> return s->capabilities[MIGRATION_CAPABILITY_FIXED_RAM]; >> -*/ >> - return false; >> } >> >> bool migrate_ignore_shared(void) >> diff --git a/migration/ram.c b/migration/ram.c >> index 92769902bb..152a03604f 100644 >> --- a/migration/ram.c >> +++ b/migration/ram.c >> @@ -1157,12 +1157,18 @@ static int save_zero_page(RAMState *rs, PageSearchStatus *pss, >> return 0; >> } >> >> + stat64_add(&mig_stats.zero_pages, 1); > > Here we keep zero page accounting, but.. > >> + >> + 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 += save_page_header(pss, file, pss->block, offset | RAM_SAVE_FLAG_ZERO); >> qemu_put_byte(file, 0); >> len += 1; >> ram_release_page(pss->block->idstr, offset); >> - >> - stat64_add(&mig_stats.zero_pages, 1); >> ram_transferred_add(len); >> >> /* >> @@ -1220,14 +1226,20 @@ static int save_normal_page(PageSearchStatus *pss, RAMBlock *block, >> { >> QEMUFile *file = pss->pss_channel; >> >> - 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)); > > .. here we ignored normal page accounting. > > I think we should have the same behavior on both, perhaps keep them always? > This is the accounting for the header only if I'm not mistaken. >> + 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); Here's the page accounting. >> @@ -2475,6 +2487,8 @@ static void ram_save_cleanup(void *opaque) >> block->clear_bmap = NULL; >> g_free(block->bmap); >> block->bmap = NULL; >> + g_free(block->shadow_bmap); >> + block->shadow_bmap = NULL; >> } >> >> xbzrle_cleanup(); >> @@ -2842,6 +2856,7 @@ static void ram_list_init_bitmaps(void) >> */ >> block->bmap = bitmap_new(pages); >> bitmap_set(block->bmap, 0, pages); >> + block->shadow_bmap = bitmap_new(block->used_length >> TARGET_PAGE_BITS); > > AFAICT bmap should also use used_length. How about adding one more patch > to change that, then you can use "pages" here? It uses max_length. I don't know what are the effects of that change. I'll look into it. > See ram_mig_ram_block_resized() where we call migration_cancel() if resized. > >> block->clear_bmap_shift = shift; >> block->clear_bmap = bitmap_new(clear_bmap_size(pages, shift)); >> } >> @@ -2979,6 +2994,44 @@ void qemu_guest_free_page_hint(void *addr, size_t len) >> } >> } >> >> +#define FIXED_RAM_HDR_VERSION 1 >> +struct FixedRamHeader { >> + uint32_t version; >> + uint64_t page_size; >> + uint64_t bitmap_offset; >> + uint64_t pages_offset; >> + /* end of v1 */ >> +} QEMU_PACKED; >> + >> +static void fixed_ram_insert_header(QEMUFile *file, RAMBlock *block) >> +{ >> + g_autofree struct FixedRamHeader *header; >> + size_t header_size, bitmap_size; >> + long num_pages; >> + >> + header = g_new0(struct FixedRamHeader, 1); >> + header_size = sizeof(struct FixedRamHeader); >> + >> + num_pages = block->used_length >> TARGET_PAGE_BITS; >> + bitmap_size = 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 = qemu_get_offset(file) + header_size; >> + block->pages_offset = ROUND_UP(block->bitmap_offset + >> + bitmap_size, 0x100000); >> + >> + header->version = cpu_to_be32(FIXED_RAM_HDR_VERSION); >> + header->page_size = cpu_to_be64(TARGET_PAGE_SIZE); > > This is the "page size" for the shadow bitmap, right? Shall we state it > somewhere (e.g. explaining why it's not block->page_size)? Ok. > It's unfortunate that we already have things like: > > if (migrate_postcopy_ram() && block->page_size != > qemu_host_page_size) { > qemu_put_be64(f, block->page_size); > } > > But indeed we can't merge them because they seem to service different > purpose. > >> + header->bitmap_offset = cpu_to_be64(block->bitmap_offset); >> + header->pages_offset = 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 >> @@ -3028,6 +3081,12 @@ 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_length, SEEK_SET); >> + } >> } >> } >> >> @@ -3061,6 +3120,20 @@ static int ram_save_setup(QEMUFile *f, void *opaque) >> return 0; >> } >> >> +static void ram_save_shadow_bmap(QEMUFile *f) >> +{ >> + RAMBlock *block; >> + >> + RAMBLOCK_FOREACH_MIGRATABLE(block) { >> + long num_pages = block->used_length >> TARGET_PAGE_BITS; >> + long bitmap_size = BITS_TO_LONGS(num_pages) * sizeof(unsigned long); >> + qemu_put_buffer_at(f, (uint8_t *)block->shadow_bmap, bitmap_size, >> + block->bitmap_offset); >> + /* to catch any thread late sending pages */ >> + block->shadow_bmap = NULL; > > What is this for? Wouldn't this leak the buffer already? > Ah this is debug code. It's because of multifd. In this series I don't use sem_sync because there's no packets. But doing so causes multifd_send_sync_main() to return before the multifd channel has sent all its pages. This is here so the channel crashes when writing the bitmap. I think it's worth it to keep it but I'd have to move it to the multifd patch and free the bitmap properly. Thanks!