From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Ostrovsky Subject: Re: [PATCH 2/2] x86/HVM: Use fixed TSC value when saving or restoring domain Date: Mon, 31 Mar 2014 11:06:41 -0400 Message-ID: <53398481.3000307@oracle.com> References: <1396148751-6918-1-git-send-email-boris.ostrovsky@oracle.com> <1396148751-6918-3-git-send-email-boris.ostrovsky@oracle.com> <533956C50200007800003B02@nat28.tlf.novell.com> <53397530.8060007@oracle.com> <5339991F0200007800003C65@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5339991F0200007800003C65@nat28.tlf.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: kevin.tian@intel.com, ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, ian.jackson@eu.citrix.com, eddie.dong@intel.com, xen-devel@lists.xen.org, jun.nakajima@intel.com, suravee.suthikulpanit@amd.com List-Id: xen-devel@lists.xenproject.org On 03/31/2014 10:34 AM, Jan Beulich wrote: > >>>> index 95b4b91..032eb23 100644 >>>> --- a/xen/include/xen/time.h >>>> +++ b/xen/include/xen/time.h >>>> @@ -32,7 +32,8 @@ struct vcpu; >>>> typedef s64 s_time_t; >>>> #define PRI_stime PRId64 >>>> >>>> -s_time_t get_s_time(void); >>>> +s_time_t get_s_time_fixed(u64 at_tick); >>>> +#define get_s_time() get_s_time_fixed(0) >>> get_s_time(), through NOW(), has quite many users, so I'm not certain >>> the code bloat resulting from this is desirable. I'd suggest the function >>> to remain such; the compiler will be able to make it a mov+jmp. >> Sorry, not sure I understand what you are asking for. >> >> There shouldn't be much of code size increase since get_s_time() >> currently (and get_s_time_fixed() after this patch is applied) are not >> inlines. The only increase is due to routine itself getting very >> slightly larger. >> >> But I suspect you meant something else. > All call sites have to zero %edi with the change in place, and I > was trying to tell you that the number of call sites of this isn't > exactly small due to the function's use via NOW(). Hence I think > you shouldn't penalize the callers and have an explicit out of line > wrapper. OK, I understand the concern now but still confused about what you want ;-( Two separate routines that only differ in how tsc is calculated (rdtscll vs. an 'in' parameter)? -boris