From: Igor Mammedov <imammedo@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, pbonzini@redhat.com
Subject: Re: [PATCH 0/5] vhost: support upto 509 memory regions
Date: Wed, 17 Jun 2015 00:19:15 +0200 [thread overview]
Message-ID: <20150617001915.23f062b0@igors-macbook-pro.local> (raw)
In-Reply-To: <20150616231505-mutt-send-email-mst@redhat.com>
On Tue, 16 Jun 2015 23:16:07 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Tue, Jun 16, 2015 at 06:33:34PM +0200, Igor Mammedov wrote:
> > Series extends vhost to support upto 509 memory regions,
> > and adds some vhost:translate_desc() performance improvemnts
> > so it won't regress when memslots are increased to 509.
> >
> > It fixes running VM crashing during memory hotplug due
> > to vhost refusing accepting more than 64 memory regions.
> >
> > It's only host kernel side fix to make it work with QEMU
> > versions that support memory hotplug. But I'll continue
> > to work on QEMU side solution to reduce amount of memory
> > regions to make things even better.
>
> I'm concerned userspace work will be harder, in particular,
> performance gains will be harder to measure.
it appears so, so far.
> How about a flag to disable caching?
I've tried to measure cost of cache miss but without much luck,
difference between version with cache and with caching removed
was within margin of error (±10ns) (i.e. not mensurable on my
5min/10*10^6 test workload).
Also I'm concerned about adding extra fetch+branch for flag
checking will make things worse for likely path of cache hit,
so I'd avoid it if possible.
Or do you mean a simple global per module flag to disable it and
wrap thing in static key so that it will be cheap jump to skip
cache?
> > Performance wise for guest with (in my case 3 memory regions)
> > and netperf's UDP_RR workload translate_desc() execution
> > time from total workload takes:
> >
> > Memory |1G RAM|cached|non cached
> > regions # | 3 | 53 | 53
> > ------------------------------------
> > upstream | 0.3% | - | 3.5%
> > ------------------------------------
> > this series | 0.2% | 0.5% | 0.7%
> >
> > where "non cached" column reflects trashing wokload
> > with constant cache miss. More details on timing in
> > respective patches.
> >
> > Igor Mammedov (5):
> > vhost: use binary search instead of linear in find_region()
> > vhost: extend memory regions allocation to vmalloc
> > vhost: support upto 509 memory regions
> > vhost: add per VQ memory region caching
> > vhost: translate_desc: optimization for desc.len < region size
> >
> > drivers/vhost/vhost.c | 95
> > +++++++++++++++++++++++++++++++++++++--------------
> > drivers/vhost/vhost.h | 1 + 2 files changed, 71 insertions(+), 25
> > deletions(-)
> >
> > --
> > 1.8.3.1
next prev parent reply other threads:[~2015-06-16 22:19 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-16 16:33 [PATCH 0/5] vhost: support upto 509 memory regions Igor Mammedov
2015-06-16 16:33 ` [PATCH 1/5] vhost: use binary search instead of linear in find_region() Igor Mammedov
2015-06-16 21:07 ` Michael S. Tsirkin
2015-06-16 21:13 ` Igor Mammedov
2015-06-16 16:33 ` [PATCH 2/5] vhost: extend memory regions allocation to vmalloc Igor Mammedov
2015-06-16 16:33 ` [PATCH 3/5] vhost: support upto 509 memory regions Igor Mammedov
2015-06-16 21:14 ` Michael S. Tsirkin
2015-06-16 22:00 ` Igor Mammedov
2015-06-17 6:34 ` Michael S. Tsirkin
2015-06-17 7:28 ` Igor Mammedov
2015-06-17 7:39 ` Michael S. Tsirkin
2015-06-17 8:54 ` Igor Mammedov
2015-06-17 10:11 ` Michael S. Tsirkin
2015-06-17 10:37 ` Igor Mammedov
2015-06-17 10:46 ` Michael S. Tsirkin
2015-06-17 11:48 ` Igor Mammedov
2015-06-17 11:51 ` Michael S. Tsirkin
2015-06-17 12:23 ` Igor Mammedov
2015-06-17 13:13 ` Michael S. Tsirkin
2015-06-17 13:20 ` Paolo Bonzini
2015-06-17 14:32 ` Michael S. Tsirkin
2015-06-17 15:12 ` Igor Mammedov
2015-06-17 15:38 ` Michael S. Tsirkin
2015-06-17 16:09 ` Igor Mammedov
2015-06-17 16:30 ` Michael S. Tsirkin
2015-06-17 16:31 ` Paolo Bonzini
2015-06-17 16:34 ` Michael S. Tsirkin
2015-06-17 16:38 ` Paolo Bonzini
2015-06-17 16:41 ` Michael S. Tsirkin
2015-06-17 16:47 ` Paolo Bonzini
2015-06-17 17:32 ` Igor Mammedov
2015-06-17 19:11 ` Michael S. Tsirkin
2015-06-17 17:30 ` Igor Mammedov
2015-06-18 9:12 ` Igor Mammedov
2015-06-18 9:50 ` Michael S. Tsirkin
2015-06-18 10:03 ` Paolo Bonzini
2015-06-18 11:39 ` Igor Mammedov
2015-06-18 11:41 ` Michael S. Tsirkin
2015-06-18 11:50 ` Paolo Bonzini
2015-06-18 13:19 ` Michael S. Tsirkin
2015-06-18 13:46 ` Paolo Bonzini
2015-06-18 14:47 ` Michael S. Tsirkin
2015-06-18 15:54 ` Igor Mammedov
2015-06-18 16:02 ` Paolo Bonzini
2015-06-19 7:56 ` Michael S. Tsirkin
2015-06-19 7:57 ` Paolo Bonzini
2015-06-19 8:05 ` Michael S. Tsirkin
2015-06-19 8:52 ` Paolo Bonzini
2015-06-19 10:14 ` Michael S. Tsirkin
2015-06-19 10:44 ` Paolo Bonzini
2015-06-19 13:34 ` Michael S. Tsirkin
2015-06-19 13:34 ` Michael S. Tsirkin
2015-06-19 15:19 ` Paolo Bonzini
2015-06-19 15:19 ` Paolo Bonzini
2015-06-19 16:20 ` Michael S. Tsirkin
2015-06-19 16:20 ` Michael S. Tsirkin
2015-06-19 16:26 ` Paolo Bonzini
2015-06-19 16:26 ` Paolo Bonzini
2015-06-19 16:33 ` Michael S. Tsirkin
2015-06-19 16:33 ` Michael S. Tsirkin
2015-06-19 16:44 ` Paolo Bonzini
2015-06-19 16:44 ` Paolo Bonzini
2015-06-22 7:10 ` Igor Mammedov
2015-06-22 7:10 ` Igor Mammedov
2015-06-22 9:45 ` Paolo Bonzini
2015-06-22 9:45 ` Paolo Bonzini
2015-06-19 16:45 ` Michael S. Tsirkin
2015-06-19 16:45 ` Michael S. Tsirkin
2015-06-19 16:50 ` Paolo Bonzini
2015-06-19 16:50 ` Paolo Bonzini
2015-06-18 12:02 ` Igor Mammedov
2015-06-17 8:53 ` Paolo Bonzini
2015-06-16 16:33 ` [PATCH 4/5] vhost: add per VQ memory region caching Igor Mammedov
2015-06-16 16:33 ` [PATCH 5/5] vhost: translate_desc: optimization for desc.len < region size Igor Mammedov
2015-06-16 21:11 ` Michael S. Tsirkin
2015-06-16 21:16 ` [PATCH 0/5] vhost: support upto 509 memory regions Michael S. Tsirkin
2015-06-16 22:19 ` Igor Mammedov [this message]
2015-06-17 6:31 ` Michael S. Tsirkin
2015-06-17 7:33 ` Igor Mammedov
2015-06-17 7:40 ` Michael S. Tsirkin
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