From: "Tan, Jianfeng" <jianfeng.tan@intel.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>,
"dev@dpdk.org" <dev@dpdk.org>
Cc: "yliu@fridaylinux.org" <yliu@fridaylinux.org>
Subject: Re: [dpdk-dev] [PATCH 4/4] vhost: avoid populate guest memory
Date: Thu, 22 Feb 2018 08:40:08 +0000 [thread overview]
Message-ID: <ED26CBA2FAD1BF48A8719AEF02201E365144B003@SHSMSX103.ccr.corp.intel.com> (raw)
In-Reply-To: <87337fa8-66fb-f9ec-45c2-78042bb47759@redhat.com>
> -----Original Message-----
> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com]
> Sent: Thursday, February 22, 2018 4:26 PM
> To: Tan, Jianfeng; dev@dpdk.org
> Cc: yliu@fridaylinux.org
> Subject: Re: [PATCH 4/4] vhost: avoid populate guest memory
>
>
>
> On 02/22/2018 03:42 AM, Tan, Jianfeng wrote:
> > Hi Maxime,
> >
> >> -----Original Message-----
> >> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com]
> >> Sent: Tuesday, February 20, 2018 4:45 AM
> >> To: Tan, Jianfeng; dev@dpdk.org
> >> Cc: yliu@fridaylinux.org
> >> Subject: Re: [PATCH 4/4] vhost: avoid populate guest memory
> >>
> >> Hi Jianfeng,
> >>
> >> On 02/14/2018 05:01 AM, Jianfeng Tan wrote:
> >>> It's not necessary to polulate guest memory from vhost side.
> >>>
> >>> Cc: maxime.coquelin@redhat.com
> >>> Cc: yliu@fridaylinux.org
> >>>
> >>> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
> >>> ---
> >>> lib/librte_vhost/vhost_user.c | 4 +++-
> >>> 1 file changed, 3 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> >>> index 90ed211..9bd0391 100644
> >>> --- a/lib/librte_vhost/vhost_user.c
> >>> +++ b/lib/librte_vhost/vhost_user.c
> >>> @@ -644,6 +644,7 @@ vhost_user_set_mem_table(struct virtio_net
> *dev,
> >> struct VhostUserMsg *pmsg)
> >>> uint64_t mmap_offset;
> >>> uint64_t alignment;
> >>> uint32_t i;
> >>> + int populate;
> >>> int fd;
> >>>
> >>> if (dev->mem && !vhost_memory_changed(&memory, dev->mem))
> >> {
> >>> @@ -714,8 +715,9 @@ vhost_user_set_mem_table(struct virtio_net
> *dev,
> >> struct VhostUserMsg *pmsg)
> >>> }
> >>> mmap_size = RTE_ALIGN_CEIL(mmap_size, alignment);
> >>>
> >>> + populate = (dev->dequeue_zero_copy) ? MAP_POPULATE :
> >> 0;
> >>> mmap_addr = mmap(NULL, mmap_size, PROT_READ |
> >> PROT_WRITE,
> >>> - MAP_SHARED | MAP_POPULATE, fd, 0);
> >>> + MAP_SHARED | populate, fd, 0);
> >>>
> >>> if (mmap_addr == MAP_FAILED) {
> >>> RTE_LOG(ERR, VHOST_CONFIG,
> >>>
> >>
> >> Wouldn't not populating all the guest memory have a bad impact on 0%
> >> acceptable loss use-cases?
> >
> > Yes, it could affect such use case; but we can address that by warming up
> the system a little bit, can't we?
>
> I'm not sure this is a good idea to ask the real user to warm-up the
> system.
>
> Also, even with benchmarking, the loss happens when the queues are full,
> so it is likely that it happens with buffers not used before, even if
> system has been warmed-up.
OK, warm-up is a bad idea here :-)
But if a VM is used for such use case, I think we'd better pre-allocate the memory at QEMU side.
>
> > From a good point of view, it could save the memory for VMs without pre-
> allocating.
>
> What could be done is maybe to have an EAL API for mmaping, with an
> associated EAL parameter to state whether it want populating or not.
> This option would be disabled by default.
>
> Does that sounds reasonable?
If we look for an application-level configuration, it's not necessary to have such a parameter. Refer to the 3rd patch in this series, if we make all (current/future) memory locked, the mmap() syscall will populate the memory.
Thanks,
Jianfeng
next prev parent reply other threads:[~2018-02-22 8:40 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-14 4:01 [dpdk-dev] [PATCH 0/4] some fixes target for 18.05 Jianfeng Tan
2018-02-14 4:01 ` [dpdk-dev] [PATCH 1/4] vhost: remove unused macro Jianfeng Tan
2018-02-19 20:49 ` Maxime Coquelin
2018-02-21 7:32 ` Maxime Coquelin
2018-02-14 4:01 ` [dpdk-dev] [PATCH 2/4] vhost: avoid function call in data path Jianfeng Tan
2018-02-19 20:48 ` Maxime Coquelin
2018-02-21 7:32 ` Maxime Coquelin
2018-02-14 4:01 ` [dpdk-dev] [PATCH 3/4] app/testpmd: add option to avoid lock all memory Jianfeng Tan
2018-02-14 6:40 ` Wu, Jingjing
2018-02-24 3:26 ` [dpdk-dev] [PATCH v2] " Jianfeng Tan
2018-04-22 23:05 ` Thomas Monjalon
2018-05-03 11:32 ` Burakov, Anatoly
2018-02-14 4:01 ` [dpdk-dev] [PATCH 4/4] vhost: avoid populate guest memory Jianfeng Tan
2018-02-19 20:44 ` Maxime Coquelin
2018-02-22 2:42 ` Tan, Jianfeng
2018-02-22 8:25 ` Maxime Coquelin
2018-02-22 8:40 ` Tan, Jianfeng [this message]
2018-02-22 12:32 ` Maxime Coquelin
2018-02-23 3:17 ` Tan, Jianfeng
2018-03-28 6:56 ` [dpdk-dev] [PATCH v2] " Jianfeng Tan
2018-03-30 8:21 ` Maxime Coquelin
2018-03-30 8:34 ` Maxime Coquelin
2018-02-21 7:35 ` [dpdk-dev] [PATCH 0/4] some fixes target for 18.05 Maxime Coquelin
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