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 X-Spam-Level: X-Spam-Status: No, score=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EA2B2C433C1 for ; Mon, 29 Mar 2021 12:05:02 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 5CB0261934 for ; Mon, 29 Mar 2021 12:05:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5CB0261934 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; 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bh=jIeG0aiGJvFD417JkZYo5YrdBQIBxVr42m5szL6O52c=; b=YzUAg8EmE9mBbhVPctQ4/XoQ7vbCkhB0o8MSO9+8k7JgdEth9577/76LYVsGHSN8Pg/Agf L7TKv1UPXPVV/FHiGtO8JYN8RUOCYAjg1krhzgGsQ1fzTUkfx8Fkx7LzSJ3knJA8qxSW1E fxywa0osHp7wkqCmQj/xer/m9sIkHZ0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-316-0DFnNf44MVKoX6BURn9z6A-1; Mon, 29 Mar 2021 08:03:10 -0400 X-MC-Unique: 0DFnNf44MVKoX6BURn9z6A-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 403B3107BEFD; Mon, 29 Mar 2021 12:03:09 +0000 (UTC) Received: from work-vm (ovpn-114-160.ams2.redhat.com [10.36.114.160]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 69E8F5C582; Mon, 29 Mar 2021 12:03:07 +0000 (UTC) Date: Mon, 29 Mar 2021 13:03:04 +0100 From: "Dr. David Alan Gilbert" To: leirao Subject: Re: [PATCH v4 08/10] Reduce the PVM stop time during Checkpoint Message-ID: References: <1616639091-28279-1-git-send-email-lei.rao@intel.com> <1616639091-28279-9-git-send-email-lei.rao@intel.com> MIME-Version: 1.0 In-Reply-To: <1616639091-28279-9-git-send-email-lei.rao@intel.com> User-Agent: Mutt/2.0.6 (2021-03-06) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: lukasstraub2@web.de, lizhijian@cn.fujitsu.com, quintela@redhat.com, jasowang@redhat.com, qemu-devel@nongnu.org, chen.zhang@intel.com, pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * leirao (lei.rao@intel.com) wrote: > From: "Rao, Lei" > > When flushing memory from ram cache to ram during every checkpoint > on secondary VM, we can copy continuous chunks of memory instead of > 4096 bytes per time to reduce the time of VM stop during checkpoint. > > Signed-off-by: Lei Rao A minor comment below, but : Reviewed-by: Dr. David Alan Gilbert > --- > migration/ram.c | 45 ++++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 42 insertions(+), 3 deletions(-) > > diff --git a/migration/ram.c b/migration/ram.c > index c69a8e0..a258466 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -822,6 +822,39 @@ unsigned long migration_bitmap_find_dirty(RAMState *rs, RAMBlock *rb, > return next; > } > > +/* > + * colo_bitmap_find_diry:find contiguous dirty pages from start > + * > + * Returns the page offset within memory region of the start of the contiguout > + * dirty page > + * > + * @rs: current RAM state > + * @rb: RAMBlock where to search for dirty pages > + * @start: page where we start the search > + * @num: the number of contiguous dirty pages > + */ > +static inline > +unsigned long colo_bitmap_find_dirty(RAMState *rs, RAMBlock *rb, > + unsigned long start, unsigned long *num) > +{ > + unsigned long size = rb->used_length >> TARGET_PAGE_BITS; > + unsigned long *bitmap = rb->bmap; > + unsigned long first, next; It might be better to add the *num = 0 here, which means this function always writes num > + if (ramblock_is_ignored(rb)) { > + return size; > + } > + > + first = find_next_bit(bitmap, size, start); > + if (first >= size) { > + return first; > + } > + next = find_next_zero_bit(bitmap, size, first + 1); > + assert(next >= first); > + *num = next - first; > + return first; > +} > + > static inline bool migration_bitmap_clear_dirty(RAMState *rs, > RAMBlock *rb, > unsigned long page) > @@ -3666,6 +3699,8 @@ void colo_flush_ram_cache(void) > void *dst_host; > void *src_host; > unsigned long offset = 0; > + unsigned long num = 0; that could move inside the while loop. > + unsigned long i = 0; This line could move inside the 'else' clause below that uses it. > memory_global_dirty_log_sync(); > WITH_RCU_READ_LOCK_GUARD() { > @@ -3679,19 +3714,23 @@ void colo_flush_ram_cache(void) > block = QLIST_FIRST_RCU(&ram_list.blocks); > > while (block) { > - offset = migration_bitmap_find_dirty(ram_state, block, offset); > + offset = colo_bitmap_find_dirty(ram_state, block, offset, &num); > > if (((ram_addr_t)offset) << TARGET_PAGE_BITS > >= block->used_length) { > offset = 0; > + num = 0; > block = QLIST_NEXT_RCU(block, next); > } else { > - migration_bitmap_clear_dirty(ram_state, block, offset); > + for (i = 0; i < num; i++) { > + migration_bitmap_clear_dirty(ram_state, block, offset + i); > + } > dst_host = block->host > + (((ram_addr_t)offset) << TARGET_PAGE_BITS); > src_host = block->colo_cache > + (((ram_addr_t)offset) << TARGET_PAGE_BITS); > - memcpy(dst_host, src_host, TARGET_PAGE_SIZE); > + memcpy(dst_host, src_host, TARGET_PAGE_SIZE * num); > + offset += num; I was initially confused as to why the old code didn't have an offset++ but I guess that means it just checked the bit a second time that was just cleared. Dave > } > } > } > -- > 1.8.3.1 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK