From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [PATCH 3/3] grant-table: defer releasing pages acquired in a grant copy Date: Thu, 22 Jan 2015 14:39:48 +0000 Message-ID: <54C10BB4.90109@citrix.com> References: <1421777990-1122-1-git-send-email-david.vrabel@citrix.com> <1421777990-1122-4-git-send-email-david.vrabel@citrix.com> <54C11875020000780005834D@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta4.messagelabs.com ([85.158.143.247]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YEIvK-0000Bd-2o for xen-devel@lists.xenproject.org; Thu, 22 Jan 2015 14:39:54 +0000 In-Reply-To: <54C11875020000780005834D@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: xen-devel@lists.xenproject.org, Keir Fraser , Ian Campbell , Tim Deegan List-Id: xen-devel@lists.xenproject.org On 22/01/15 14:34, Jan Beulich wrote: >>>> On 20.01.15 at 19:19, wrote: >> Acquiring a page for the source or destination of a grant copy is an >> expensive operation. A common use case is for two adjacent grant copy >> ops to operate on either the same source or the same destination page. >> >> Instead of always acquiring and releasing destination and source pages >> for each operation, release the page once it is no longer valid for >> the next op. >> >> If either the source or destination domains changes both pages are >> released as it is unlikely that either will still be valid. >> >> XenServer's performance benchmarks show modest improvements in network >> receive throughput (netback uses grant copy in the guest Rx path) and >> no regressions in disk performamnce (using tapdisk3 which grant copies >> as the backend). [...] >> +static bool_t gnttab_copy_buf_valid(const struct gnttab_copy *op, >> + const struct gnttab_copy_ptr *p, >> + const struct gnttab_copy_buf *b, >> + unsigned int gref_flag) >> +{ >> + if ( !b->virt ) >> + return 0; >> + if ( op->flags & gref_flag ) >> + return b->have_grant && p->u.ref == b->ptr.u.ref; >> + return p->u.gmfn == b->ptr.u.gmfn; >> +} > > ... whether you wouldn't better fold the op and gref_flag parameters > into one, as they're used only once and only together. Do you mean something like? static bool_t gnttab_copy_buf_valid(const struct gnttab_copy_ptr *p, const struct gnttab_copy_buf *b, bool_t is_gref) David