From patchwork Mon Sep 25 18:55:34 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jennifer Herbert X-Patchwork-Id: 9970367 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 2CD2C60365 for ; Mon, 25 Sep 2017 18:58:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 103C7288D0 for ; Mon, 25 Sep 2017 18:58:45 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 04E1428CB8; Mon, 25 Sep 2017 18:58:45 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 49D2528ABC for ; Mon, 25 Sep 2017 18:58:44 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dwYYD-0000zG-Uv; Mon, 25 Sep 2017 18:56:17 +0000 Received: from mail6.bemta6.messagelabs.com ([193.109.254.103]) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dwYYC-0000yX-O9 for xen-devel@lists.xenproject.org; Mon, 25 Sep 2017 18:56:16 +0000 Received: from [193.109.254.147] by server-10.bemta-6.messagelabs.com id 35/82-03642-05159C95; Mon, 25 Sep 2017 18:56:16 +0000 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFupjkeJIrShJLcpLzFFi42JxWrrBXtc/8GS kQVefoMX3LZOZHBg9Dn+4whLAGMWamZeUX5HAmrH930TWgs8hFW/uNbM3MHY5dDFyckgI+Evc /jabsYuRg4NNwETizYPQLkYuDhGBFkaJxad2sYPEmQWMJNqOcoOUCwtYSSxffocVJMwioCrRs 1ARxOQV8JFYsJMFYqCCxJSH75lBbE4BX4k9fw+wgdhCQCWbmt5C2RoSZxcsYgWxeQUEJU7OfA LWyywgIXHwxQvmCYy8s5CkZiFJLWBkWsWoUZxaVJZapGtsoJdUlJmeUZKbmJmja2hgppebWly cmJ6ak5hUrJecn7uJERg2DECwg/Hv2sBDjJIcTEqivHf5TkQK8SXlp1RmJBZnxBeV5qQWH2KU 4eBQkuAtDTgZKSRYlJqeWpGWmQMMYJi0BAePkgjvTX+gNG9xQWJucWY6ROoUoy5Hx827f5iEW PLy81KlxHmFQGYIgBRllObBjYBF0yVGWSlhXkago4R4ClKLcjNLUOVfMYpzMCoJQ6ziycwrgd v0CugIJqAjeqeeADmiJBEhJdXAaFDSb3x7zsrJVx+2qC689OLrmnclx6I1a59Nn7JhT27JnPP yV2OFGVueVolMybdSn/ZmnfeyvwlZWl/kzPnNmmbMW510Q0uBYerGcLscuc4tFd3mpz/77NyR POu5TIdMcoDOl5ye17yB5velaw5Vnzkmu9us0rdJ6SrvOofM7HTmLfMDvh8+rcRSnJFoqMVcV JwIAOtz572hAgAA X-Env-Sender: prvs=434979fdc=jennifer.herbert@citrix.com X-Msg-Ref: server-3.tower-27.messagelabs.com!1506365773!118149178!1 X-Originating-IP: [66.165.176.63] X-SpamReason: No, hits=0.0 required=7.0 tests=sa_preprocessor: VHJ1c3RlZCBJUDogNjYuMTY1LjE3Ni42MyA9PiAzMDYwNDg=\n, received_headers: No Received headers X-StarScan-Received: X-StarScan-Version: 9.4.45; banners=-,-,- X-VirusChecked: Checked Received: (qmail 41638 invoked from network); 25 Sep 2017 18:56:14 -0000 Received: from smtp02.citrix.com (HELO SMTP02.CITRIX.COM) (66.165.176.63) by server-3.tower-27.messagelabs.com with RC4-SHA encrypted SMTP; 25 Sep 2017 18:56:14 -0000 X-IronPort-AV: E=Sophos;i="5.42,437,1500940800"; d="scan'208";a="449153890" From: Jennifer Herbert To: Ian Jackson , Wei Liu , , Date: Mon, 25 Sep 2017 19:55:34 +0100 Message-ID: <1506365735-133776-3-git-send-email-Jennifer.Herbert@citrix.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1506365735-133776-1-git-send-email-Jennifer.Herbert@citrix.com> References: <1506365735-133776-1-git-send-email-Jennifer.Herbert@citrix.com> MIME-Version: 1.0 Cc: Jennifer Herbert Subject: [Xen-devel] [PATCH v3 2/3] Introduce migration precopy policy X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" X-Virus-Scanned: ClamAV using ClamSMTP This Patch allows a migration precopy policy to be specified. The precopy phase of the xc_domain_save() live migration algorithm has historically been implemented to run until either a) (almost) no pages are dirty or b) some fixed, hard-coded maximum number of precopy iterations has been exceeded. This policy and its implementation are less than ideal for a few reasons: - the logic of the policy is intertwined with the control flow of the mechanism of the precopy stage - it can't take into account facts external to the immediate migration context, such external state transfer state, interactive user input, or the passage of wall-clock time. - it does not permit the user to change their mind, over time, about what to do at the end of the precopy (they get an unconditional transition into the stop-and-copy phase of the migration) To permit callers to implement arbitrary higher-level policies governing when the live migration precopy phase should end, and what should be done next: - add a precopy_policy() callback to the xc_domain_save() user-supplied callbacks - during the precopy phase of live migrations, consult this policy after each batch of pages transmitted and take the dictated action, which may be to a) abort the migration entirely, b) continue with the precopy, or c) proceed to the stop-and-copy phase. - provide an implementation of the old policy, used when precopy_policy callback is not provided. Signed-off-by: Jennifer Herbert Signed-off-by: Joshua Otto Reviewed-by: Paul Durrant Acked-by: Wei Liu --- v3: Have changed/added comments, removed iteration parmeter from update_progress_string and made a few formatting corrections. v2: Have made a few formatting corrections, added typedef as suggested. This is updated/modified subset of patch 7/20, part of Joshua Otto's "Add postcopy live migration support." patch, dated 27th March 2017. As indicated on the original thread, I wish to make use of this this within the XenServer product. I hope this will aid Josh in pushing the remainder of his series. --- tools/libxc/include/xenguest.h | 37 +++++++++++++-- tools/libxc/xc_sr_common.h | 6 +-- tools/libxc/xc_sr_save.c | 105 ++++++++++++++++++++++++++++------------- 3 files changed, 109 insertions(+), 39 deletions(-) diff --git a/tools/libxc/include/xenguest.h b/tools/libxc/include/xenguest.h index 6626f0c..de97f1b 100644 --- a/tools/libxc/include/xenguest.h +++ b/tools/libxc/include/xenguest.h @@ -39,6 +39,20 @@ */ struct xenevtchn_handle; +/* For save's precopy_policy(). */ +struct precopy_stats +{ + unsigned int iteration; + unsigned int total_written; + long dirty_count; /* -1 if unknown */ +}; + +/* + * A precopy_policy callback may not be running in the same address + * space as libxc an so precopy_stats is passed by value. + */ +typedef int (*precopy_policy_t)(struct precopy_stats, void *); + /* callbacks provided by xc_domain_save */ struct save_callbacks { /* Called after expiration of checkpoint interval, @@ -46,7 +60,22 @@ struct save_callbacks { */ int (*suspend)(void* data); - /* Called after the guest's dirty pages have been + /* + * Called before and after every batch of page data sent during + * the precopy phase of a live migration to ask the caller what + * to do next based on the current state of the precopy migration. + * + * Should return one of the values listed below: + */ +#define XGS_POLICY_ABORT (-1) /* Abandon the migration entirely + * and tidy up. */ +#define XGS_POLICY_CONTINUE_PRECOPY 0 /* Remain in the precopy phase. */ +#define XGS_POLICY_STOP_AND_COPY 1 /* Immediately suspend and transmit the + * remaining dirty pages. */ + precopy_policy_t precopy_policy; + + /* + * Called after the guest's dirty pages have been * copied into an output buffer. * Callback function resumes the guest & the device model, * returns to xc_domain_save. @@ -55,7 +84,8 @@ struct save_callbacks { */ int (*postcopy)(void* data); - /* Called after the memory checkpoint has been flushed + /* + * Called after the memory checkpoint has been flushed * out into the network. Typical actions performed in this * callback include: * (a) send the saved device model state (for HVM guests), @@ -65,7 +95,8 @@ struct save_callbacks { * * returns: * 0: terminate checkpointing gracefully - * 1: take another checkpoint */ + * 1: take another checkpoint + */ int (*checkpoint)(void* data); /* diff --git a/tools/libxc/xc_sr_common.h b/tools/libxc/xc_sr_common.h index a83f22a..3635704 100644 --- a/tools/libxc/xc_sr_common.h +++ b/tools/libxc/xc_sr_common.h @@ -198,12 +198,10 @@ struct xc_sr_context /* Further debugging information in the stream. */ bool debug; - /* Parameters for tweaking live migration. */ - unsigned max_iterations; - unsigned dirty_threshold; - unsigned long p2m_size; + struct precopy_stats stats; + xen_pfn_t *batch_pfns; unsigned nr_batch_pfns; unsigned long *deferred_pages; diff --git a/tools/libxc/xc_sr_save.c b/tools/libxc/xc_sr_save.c index 1e7502d..5a40e58 100644 --- a/tools/libxc/xc_sr_save.c +++ b/tools/libxc/xc_sr_save.c @@ -446,14 +446,13 @@ static int enable_logdirty(struct xc_sr_context *ctx) return 0; } -static int update_progress_string(struct xc_sr_context *ctx, - char **str, unsigned iter) +static int update_progress_string(struct xc_sr_context *ctx, char **str) { xc_interface *xch = ctx->xch; char *new_str = NULL; + unsigned int iter = ctx->save.stats.iteration; - if ( asprintf(&new_str, "Frames iteration %u of %u", - iter, ctx->save.max_iterations) == -1 ) + if ( asprintf(&new_str, "Frames iteration %u", iter) == -1 ) { PERROR("Unable to allocate new progress string"); return -1; @@ -467,6 +466,28 @@ static int update_progress_string(struct xc_sr_context *ctx, } /* + * This is the live migration precopy policy - it's called periodically during + * the precopy phase of live migrations, and is responsible for deciding when + * the precopy phase should terminate and what should be done next. + * + * The policy implemented here behaves identically to the policy previously + * hard-coded into xc_domain_save() - it proceeds to the stop-and-copy phase of + * the live migration when there are either fewer than 50 dirty pages, or more + * than 5 precopy rounds have completed. + */ +#define SPP_MAX_ITERATIONS 5 +#define SPP_TARGET_DIRTY_COUNT 50 + +static int simple_precopy_policy(struct precopy_stats stats, void *user) +{ + return ((stats.dirty_count >= 0 && + stats.dirty_count < SPP_TARGET_DIRTY_COUNT) || + stats.iteration >= SPP_MAX_ITERATIONS) + ? XGS_POLICY_STOP_AND_COPY + : XGS_POLICY_CONTINUE_PRECOPY; +} + +/* * Send memory while guest is running. */ static int send_memory_live(struct xc_sr_context *ctx) @@ -474,21 +495,59 @@ static int send_memory_live(struct xc_sr_context *ctx) xc_interface *xch = ctx->xch; xc_shadow_op_stats_t stats = { 0, ctx->save.p2m_size }; char *progress_str = NULL; - unsigned x; + unsigned int x = 0; int rc; + int policy_decision; - rc = update_progress_string(ctx, &progress_str, 0); - if ( rc ) - goto out; + DECLARE_HYPERCALL_BUFFER_SHADOW(unsigned long, dirty_bitmap, + &ctx->save.dirty_bitmap_hbuf); - rc = send_all_pages(ctx); + precopy_policy_t precopy_policy = ctx->save.callbacks->precopy_policy; + void *data = ctx->save.callbacks->data; + + struct precopy_stats *policy_stats; + + rc = update_progress_string(ctx, &progress_str); if ( rc ) goto out; - for ( x = 1; - ((x < ctx->save.max_iterations) && - (stats.dirty_count > ctx->save.dirty_threshold)); ++x ) + ctx->save.stats = (struct precopy_stats) + { .dirty_count = ctx->save.p2m_size }; + policy_stats = &ctx->save.stats; + + if ( precopy_policy == NULL ) + precopy_policy = simple_precopy_policy; + + bitmap_set(dirty_bitmap, ctx->save.p2m_size); + + for ( ; ; ) { + policy_decision = precopy_policy(*policy_stats, data); + x++; + + if ( stats.dirty_count > 0 && policy_decision != XGS_POLICY_ABORT ) + { + rc = update_progress_string(ctx, &progress_str); + if ( rc ) + goto out; + + rc = send_dirty_pages(ctx, stats.dirty_count); + if ( rc ) + goto out; + } + + if ( policy_decision != XGS_POLICY_CONTINUE_PRECOPY ) + break; + + policy_stats->iteration = x; + policy_stats->total_written += policy_stats->dirty_count; + policy_stats->dirty_count = -1; + + policy_decision = precopy_policy(*policy_stats, data); + + if ( policy_decision != XGS_POLICY_CONTINUE_PRECOPY ) + break; + if ( xc_shadow_control( xch, ctx->domid, XEN_DOMCTL_SHADOW_OP_CLEAN, &ctx->save.dirty_bitmap_hbuf, ctx->save.p2m_size, @@ -499,16 +558,8 @@ static int send_memory_live(struct xc_sr_context *ctx) goto out; } - if ( stats.dirty_count == 0 ) - break; + policy_stats->dirty_count = stats.dirty_count; - rc = update_progress_string(ctx, &progress_str, x); - if ( rc ) - goto out; - - rc = send_dirty_pages(ctx, stats.dirty_count); - if ( rc ) - goto out; } out: @@ -600,8 +651,7 @@ static int suspend_and_send_dirty(struct xc_sr_context *ctx) if ( ctx->save.live ) { - rc = update_progress_string(ctx, &progress_str, - ctx->save.max_iterations); + rc = update_progress_string(ctx, &progress_str); if ( rc ) goto out; } @@ -937,15 +987,6 @@ int xc_domain_save(xc_interface *xch, int io_fd, uint32_t dom, stream_type == XC_MIG_STREAM_REMUS || stream_type == XC_MIG_STREAM_COLO); - /* - * TODO: Find some time to better tweak the live migration algorithm. - * - * These parameters are better than the legacy algorithm especially for - * busy guests. - */ - ctx.save.max_iterations = 5; - ctx.save.dirty_threshold = 50; - /* Sanity checks for callbacks. */ if ( hvm ) assert(callbacks->switch_qemu_logdirty);