From patchwork Thu Dec 5 23:19:08 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniil Tatianin X-Patchwork-Id: 13896088 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 764F9E77170 for ; Thu, 5 Dec 2024 23:20:48 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tJL8Q-00056S-1c; Thu, 05 Dec 2024 18:19:50 -0500 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 1tJL8N-00055r-Qw for qemu-devel@nongnu.org; Thu, 05 Dec 2024 18:19:47 -0500 Received: from forwardcorp1a.mail.yandex.net ([178.154.239.72]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tJL8M-0000X4-0B for qemu-devel@nongnu.org; Thu, 05 Dec 2024 18:19:47 -0500 Received: from mail-nwsmtp-smtp-corp-main-62.myt.yp-c.yandex.net (mail-nwsmtp-smtp-corp-main-62.myt.yp-c.yandex.net [IPv6:2a02:6b8:c12:44a0:0:640:8777:0]) by forwardcorp1a.mail.yandex.net (Yandex) with ESMTPS id A5C1D60B65; Fri, 6 Dec 2024 02:19:39 +0300 (MSK) Received: from d-tatianin-lin.yandex-team.ru (unknown [2a02:6b8:b081:19::1:8]) by mail-nwsmtp-smtp-corp-main-62.myt.yp-c.yandex.net (smtpcorp/Yandex) with ESMTPSA id UJrB130IfiE0-JD04mrXL; Fri, 06 Dec 2024 02:19:39 +0300 X-Yandex-Fwd: 1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1733440779; bh=OEy7/g4ZeJLYdVU3hV0Pv8T+p/lDzE3tCioeLBtxyHE=; h=Message-Id:Date:In-Reply-To:Cc:Subject:References:To:From; b=WueW0+k/5T74Hurd8EFOdkTZVkY6FAhuNaQ2u+4ivsFbPUXREvFeXUd1o6C9cDLJZ uQzPxaekSTTX2fo56iWu/+iQbk6Jg3bPNVQYG3Gv6u7uKPWpJqUaN1wBcLLsRYUhhE fPUpDwL8NMAQ13db2VuFc1Cx3+Jwi9hN5lr2wfSc= Authentication-Results: mail-nwsmtp-smtp-corp-main-62.myt.yp-c.yandex.net; dkim=pass header.i=@yandex-team.ru From: Daniil Tatianin To: Paolo Bonzini Cc: Daniil Tatianin , Stefan Weil , Peter Xu , Fabiano Rosas , qemu-devel@nongnu.org Subject: [PATCH 2/2] overcommit: introduce mem-lock-onfault Date: Fri, 6 Dec 2024 02:19:08 +0300 Message-Id: <20241205231909.1161950-3-d-tatianin@yandex-team.ru> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20241205231909.1161950-1-d-tatianin@yandex-team.ru> References: <20241205231909.1161950-1-d-tatianin@yandex-team.ru> MIME-Version: 1.0 Received-SPF: pass client-ip=178.154.239.72; envelope-from=d-tatianin@yandex-team.ru; helo=forwardcorp1a.mail.yandex.net 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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Locking the memory without MCL_ONFAULT instantly prefaults any mmaped anonymous memory with a write-fault, which introduces a lot of extra overhead in terms of memory usage when all you want to do is to prevent kcompactd from migrating and compacting QEMU pages. Add an option to only lock pages lazily as they're faulted by the process by using MCL_ONFAULT if asked. Signed-off-by: Daniil Tatianin --- include/sysemu/sysemu.h | 1 + migration/postcopy-ram.c | 4 ++-- qemu-options.hx | 13 ++++++++++--- system/globals.c | 1 + system/vl.c | 18 ++++++++++++++++-- 5 files changed, 30 insertions(+), 7 deletions(-) diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h index 7ec419ce13..b6519c3c1e 100644 --- a/include/sysemu/sysemu.h +++ b/include/sysemu/sysemu.h @@ -44,6 +44,7 @@ extern const char *keyboard_layout; extern int old_param; extern uint8_t *boot_splash_filedata; extern bool enable_mlock; +extern bool enable_mlock_onfault; extern bool enable_cpu_pm; extern QEMUClockType rtc_clock; diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index 36ec6a3d75..8ff8c73a27 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -651,8 +651,8 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis) mis->have_fault_thread = false; } - if (enable_mlock) { - if (os_mlock(false) < 0) { + if (enable_mlock || enable_mlock_onfault) { + if (os_mlock(enable_mlock_onfault) < 0) { error_report("mlock: %s", strerror(errno)); /* * It doesn't feel right to fail at this point, we have a valid diff --git a/qemu-options.hx b/qemu-options.hx index dacc9790a4..477e0e439a 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -4566,21 +4566,28 @@ SRST ERST DEF("overcommit", HAS_ARG, QEMU_OPTION_overcommit, - "-overcommit [mem-lock=on|off][cpu-pm=on|off]\n" + "-overcommit [mem-lock=on|off][mem-lock-onfault=on|off][cpu-pm=on|off]\n" " run qemu with overcommit hints\n" " mem-lock=on|off controls memory lock support (default: off)\n" + " mem-lock-onfault=on|off controls memory lock on fault support (default: off)\n" " cpu-pm=on|off controls cpu power management (default: off)\n", QEMU_ARCH_ALL) SRST ``-overcommit mem-lock=on|off`` \ +``-overcommit mem-lock-onfault=on|off`` + \ ``-overcommit cpu-pm=on|off`` Run qemu with hints about host resource overcommit. The default is to assume that host overcommits all resources. Locking qemu and guest memory can be enabled via ``mem-lock=on`` - (disabled by default). This works when host memory is not - overcommitted and reduces the worst-case latency for guest. + or ``mem-lock-onfault=on`` (disabled by default). This works when + host memory is not overcommitted and reduces the worst-case latency for + guest. The on-fault option is better for reducing the memory footprint + since it makes allocations lazy, but the pages still get locked in place + once faulted by the guest or QEMU. Note that the two options are mutually + exclusive. Guest ability to manage power state of host cpus (increasing latency for other processes on the same host cpu, but decreasing latency for diff --git a/system/globals.c b/system/globals.c index 84ce943ac9..43501fe690 100644 --- a/system/globals.c +++ b/system/globals.c @@ -35,6 +35,7 @@ enum vga_retrace_method vga_retrace_method = VGA_RETRACE_DUMB; int display_opengl; const char* keyboard_layout; bool enable_mlock; +bool enable_mlock_onfault; bool enable_cpu_pm; int autostart = 1; int vga_interface_type = VGA_NONE; diff --git a/system/vl.c b/system/vl.c index 03819a80ef..89477f38bc 100644 --- a/system/vl.c +++ b/system/vl.c @@ -349,6 +349,10 @@ static QemuOptsList qemu_overcommit_opts = { .name = "mem-lock", .type = QEMU_OPT_BOOL, }, + { + .name = "mem-lock-onfault", + .type = QEMU_OPT_BOOL, + }, { .name = "cpu-pm", .type = QEMU_OPT_BOOL, @@ -792,8 +796,8 @@ static QemuOptsList qemu_run_with_opts = { static void realtime_init(void) { - if (enable_mlock) { - if (os_mlock(false) < 0) { + if (enable_mlock || enable_mlock_onfault) { + if (os_mlock(enable_mlock_onfault) < 0) { error_report("locking memory failed"); exit(1); } @@ -3537,7 +3541,17 @@ void qemu_init(int argc, char **argv) if (!opts) { exit(1); } + enable_mlock = qemu_opt_get_bool(opts, "mem-lock", enable_mlock); + enable_mlock_onfault = qemu_opt_get_bool(opts, + "mem-lock-onfault", + enable_mlock_onfault); + if (enable_mlock && enable_mlock_onfault) { + error_report("mem-lock and mem-lock-onfault are mutually" + "exclusive"); + exit(1); + } + enable_cpu_pm = qemu_opt_get_bool(opts, "cpu-pm", enable_cpu_pm); break; case QEMU_OPTION_compat: