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 8B151C25B47 for ; Wed, 25 Oct 2023 09:40:25 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qvaN0-0006Me-Um; Wed, 25 Oct 2023 05:40:11 -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 1qvaMy-0006MN-IJ for qemu-devel@nongnu.org; Wed, 25 Oct 2023 05:40:08 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qvaMw-00040I-7H for qemu-devel@nongnu.org; Wed, 25 Oct 2023 05:40:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1698226804; h=from:from:reply-to:reply-to:subject:subject: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=DDVvz4A6aFOClrfBCbakUVyVJH0P1QRjoM/8EAzndQ0=; b=e0Q7oSqC+ww/F6EBaX8O1Kr6nlZBhpVWVB1a9LgXrsUT5sxIN2hp6VL74jdiwSqdn2rvM+ Qrn2FZaPKX6z8ogSR6mRqdIVWQyBnsMxyjpFK2CoaZiSDsgE5lJMn1D8pagRuV311VIiWZ sRmxXqAfV7Vfq/C+MNf8nU5R5Ypz9eM= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-65-Odarfo2LMIWl6ZraWHQm_w-1; Wed, 25 Oct 2023 05:40:02 -0400 X-MC-Unique: Odarfo2LMIWl6ZraWHQm_w-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0BDBA3813F2C; Wed, 25 Oct 2023 09:40:02 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.154]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 53ECEC15BBC; Wed, 25 Oct 2023 09:40:00 +0000 (UTC) Date: Wed, 25 Oct 2023 10:39:58 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Fabiano Rosas Cc: qemu-devel@nongnu.org, armbru@redhat.com, Juan Quintela , Peter Xu , 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 Message-ID: References: <20231023203608.26370-1-farosas@suse.de> <20231023203608.26370-16-farosas@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20231023203608.26370-16-farosas@suse.de> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org 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)|... Clearer to diagram this vertically I think --------------------- | ramblock 1 header | --------------------- | ramblock 2 header | --------------------- | ... | --------------------- | ramblock n 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 If I'm reading the code correctly the new format has some padding such that each "ramblock pages" region starts on a 1 MB boundary. eg so we get: -------------------------------- | ramblock 1 header | -------------------------------- | ramblock 1 fixed-ram header | -------------------------------- | padding to next 1MB boundary | | ... | -------------------------------- | ramblock 1 pages | | ... | -------------------------------- | ramblock 2 header | -------------------------------- | ramblock 2 fixed-ram header | -------------------------------- | padding to next 1MB boundary | | ... | -------------------------------- | 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 > --- > 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); > + > + 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)); > + 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); > @@ -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); > 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); The 0x100000 gives us our 1 MB alignment. This is quite an important thing, so can we put a nice clear constant at the top of the file: /* Align fixed-ram pages data to the next 1 MB boundary */ #define FIXED_RAM_PAGE_OFFSET_ALIGNMENT 0x100000 > @@ -3179,7 +3252,6 @@ out: > qemu_put_be64(f, RAM_SAVE_FLAG_EOS); > qemu_fflush(f); > ram_transferred_add(8); > - > ret = qemu_file_get_error(f); > } > if (ret < 0) { Supurious whitspace change, possibly better in whatever patch introduced it, or dropped ? With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|