From: Jan Beulich <jbeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>,
Ian Jackson <iwj@xenproject.org>,
Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
Julien Grall <julien@xen.org>,
Dario Faggioli <dfaggioli@suse.com>,
Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH 4/6] x86/trace: Reduce stack usage from HVMTRACE_ND()
Date: Mon, 20 Sep 2021 15:00:12 +0200 [thread overview]
Message-ID: <f52efb10-7762-9828-e8c4-ce2d00acdff5@suse.com> (raw)
In-Reply-To: <e116bff4-9080-1629-221d-f2ba3255d03e@citrix.com>
On 20.09.2021 13:02, Andrew Cooper wrote:
> On 20/09/2021 10:05, Jan Beulich wrote:
>> On 17.09.2021 10:45, Andrew Cooper wrote:
>>> It is pointless to write all 6 entries and only consume the useful subset.
>>> bloat-o-meter shows quite how obscene the overhead is in vmx_vmexit_handler(),
>>> weighing in at 11% of the function arranging unread zeroes on the stack, and
>>> 8% for svm_vmexit_handler().
>>>
>>> add/remove: 0/0 grow/shrink: 0/20 up/down: 0/-1867 (-1867)
>>> Function old new delta
>>> hvm_msr_write_intercept 1049 1033 -16
>>> vmx_enable_intr_window 238 214 -24
>>> svm_enable_intr_window 337 313 -24
>>> hvmemul_write_xcr 115 91 -24
>>> hvmemul_write_cr 350 326 -24
>>> hvmemul_read_xcr 115 91 -24
>>> hvmemul_read_cr 146 122 -24
>>> hvm_mov_to_cr 438 414 -24
>>> hvm_mov_from_cr 253 229 -24
>>> vmx_intr_assist 1150 1118 -32
>>> svm_intr_assist 459 427 -32
>>> hvm_rdtsc_intercept 138 106 -32
>>> hvm_msr_read_intercept 898 866 -32
>>> vmx_vmenter_helper 1142 1094 -48
>>> vmx_inject_event 813 765 -48
>>> svm_vmenter_helper 238 190 -48
>>> hvm_hlt 197 146 -51
>>> svm_inject_event 1678 1614 -64
>>> svm_vmexit_handler 5880 5416 -464
>>> vmx_vmexit_handler 7281 6473 -808
>>> Total: Before=3644184, After=3642317, chg -0.05%
>>>
>>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> Reviewed-by: Jan Beulich <jbeulich@suse.com>
>
> Thanks, but this is buggy. There are direct callers of HVMTRACE_ND()
> which need adjustments too.
Is this really "buggy" and "need" and not merely "incomplete" and
"want"? (Just for my own understanding in terms of what I may have
overlooked.)
Jan
next prev parent reply other threads:[~2021-09-20 13:00 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-17 8:45 [PATCH 0/6] xen/trace: Fix leakage of uninitialised stack into the tracebuffer Andrew Cooper
2021-09-17 8:45 ` [PATCH 1/6] xen/trace: Don't over-read trace objects Andrew Cooper
2021-09-17 12:58 ` Jan Beulich
2021-09-17 13:26 ` Andrew Cooper
2021-09-20 8:00 ` Jan Beulich
2021-09-20 10:24 ` Andrew Cooper
2021-09-17 8:45 ` [PATCH 2/6] xen/memory: Remove tail padding from TRC_MEM_* records Andrew Cooper
2021-09-17 13:04 ` Jan Beulich
2021-09-17 8:45 ` [PATCH 3/6] xen/credit2: Remove tail padding from TRC_CSCHED2_* records Andrew Cooper
2021-09-17 13:10 ` Jan Beulich
2021-09-17 13:28 ` Andrew Cooper
2021-09-17 8:45 ` [PATCH 4/6] x86/trace: Reduce stack usage from HVMTRACE_ND() Andrew Cooper
2021-09-20 9:05 ` Jan Beulich
2021-09-20 11:02 ` Andrew Cooper
2021-09-20 13:00 ` Jan Beulich [this message]
2021-09-17 8:45 ` [PATCH 5/6] xen/credit2: Clean up trace handling Andrew Cooper
2021-09-20 9:11 ` Jan Beulich
2021-09-17 8:45 ` [PATCH 6/6] xen/trace: Minor code cleanup Andrew Cooper
2021-09-20 9:15 ` Jan Beulich
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