From patchwork Mon Sep 12 05:53:56 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juergen Gross X-Patchwork-Id: 12973268 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.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 53831ECAAD5 for ; Mon, 12 Sep 2022 05:54:39 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.405422.647884 (Exim 4.92) (envelope-from ) id 1oXcOc-0007RQ-21; Mon, 12 Sep 2022 05:54:14 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 405422.647884; Mon, 12 Sep 2022 05:54:14 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1oXcOb-0007RJ-Un; Mon, 12 Sep 2022 05:54:13 +0000 Received: by outflank-mailman (input) for mailman id 405422; Mon, 12 Sep 2022 05:54:12 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1oXcOa-00078t-4d for xen-devel@lists.xenproject.org; Mon, 12 Sep 2022 05:54:12 +0000 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 52a17d56-325f-11ed-a31c-8f8a9ae3403f; Mon, 12 Sep 2022 07:54:11 +0200 (CEST) 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 B3E25227C6; Mon, 12 Sep 2022 05:54:10 +0000 (UTC) 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 6E504139BE; Mon, 12 Sep 2022 05:54:10 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id HJuEGYLJHmMuawAAMHmgww (envelope-from ); Mon, 12 Sep 2022 05:54:10 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 52a17d56-325f-11ed-a31c-8f8a9ae3403f DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1662962050; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Ul1iFRnyaP+EjSwgFYHlOg+ezwj9WuwKzmQ6FnbRLy4=; b=ObwtyCGROAgkmoE9giDM1R+ryoK6UHuHq00FAOvQdcf+/7Kcq3LYYFsMD3OgNI7pZxuh8h cNs+ByOJlNBuI2UDlgaezEtW6bXLf0Xn+/YhDmNoLEpURH3UrT66OeeGAhoY1GJlecgOCR RMG6MXrMqlGp88Hr5SVcSgVXuoA9LYs= From: Juergen Gross To: xen-devel@lists.xenproject.org Cc: Juergen Gross , Andrew Cooper , George Dunlap , Jan Beulich , Julien Grall , Stefano Stabellini , Wei Liu Subject: [PATCH 2/2] xen/gnttab: reduce size of struct active_grant_entry Date: Mon, 12 Sep 2022 07:53:56 +0200 Message-Id: <20220912055356.24064-3-jgross@suse.com> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20220912055356.24064-1-jgross@suse.com> References: <20220912055356.24064-1-jgross@suse.com> MIME-Version: 1.0 The size of struct active_grant_entry for 64-bit builds is 40 or 48 bytes today (with or without NDEBUG). It can easily be reduced by 8 bytes by replacing the trans_domain pointer with the domid of the related domain. trans_domain is only ever used for transitive grants, which last known user has been the old Xenolinux branch of the Linux kernel. This reduction will result in less memory usage and (for production builds) in faster code, as indexing into the active_grant_entry array will be much easier with an entry having a power-of-2 size. The performance loss when using transitive grants shouldn't really matter, given the probability that those aren't in use at all today. Signed-off-by: Juergen Gross --- xen/common/grant_table.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c index fba329dcc2..8e4bbe3824 100644 --- a/xen/common/grant_table.c +++ b/xen/common/grant_table.c @@ -381,13 +381,13 @@ struct active_grant_entry { }) domid_t domid; /* Domain being granted access. */ + domid_t trans_domid; /* Domain granting access. */ unsigned int start:15; /* For sub-page grants, the start offset in the page. */ bool is_sub_page:1; /* True if this is a sub-page grant. */ unsigned int length:16; /* For sub-page grants, the length of the grant. */ grant_ref_t trans_gref; - struct domain *trans_domain; mfn_t mfn; /* Machine frame being granted. */ #ifndef NDEBUG gfn_t gfn; /* Guest's idea of the frame being granted. */ @@ -1095,7 +1095,7 @@ map_grant_ref( act->start = 0; act->length = PAGE_SIZE; act->is_sub_page = false; - act->trans_domain = rd; + act->trans_domid = rd->domain_id; act->trans_gref = ref; } } @@ -2494,7 +2494,8 @@ release_grant_for_copy( else { status = &status_entry(rgt, gref); - td = act->trans_domain; + td = (act->trans_domid == rd->domain_id) + ? rd : domid_to_domain(act->trans_domid); trans_gref = act->trans_gref; } @@ -2657,7 +2658,7 @@ acquire_grant_for_copy( !mfn_eq(act->mfn, grant_mfn) || act->start != trans_page_off || act->length != trans_length || - act->trans_domain != td || + act->trans_domid != td->domain_id || act->trans_gref != trans_gref || !act->is_sub_page)) ) { @@ -2676,7 +2677,7 @@ acquire_grant_for_copy( act->domid = ldom; act->start = trans_page_off; act->length = trans_length; - act->trans_domain = td; + act->trans_domid = td->domain_id; act->trans_gref = trans_gref; act->mfn = grant_mfn; act_set_gfn(act, INVALID_GFN); @@ -2738,7 +2739,7 @@ acquire_grant_for_copy( act->is_sub_page = is_sub_page; act->start = trans_page_off; act->length = trans_length; - act->trans_domain = td; + act->trans_domid = td->domain_id; act->trans_gref = trans_gref; act->mfn = grant_mfn; }