From: "Benjamin Coddington" <bcodding@redhat.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: "Olga Kornievskaia" <aglo@umich.edu>,
linux-nfs <linux-nfs@vger.kernel.org>
Subject: Re: unsharing tcp connections from different NFS mounts
Date: Wed, 07 Oct 2020 07:27:26 -0400 [thread overview]
Message-ID: <57E3293C-5C49-4A80-957B-E490E6A9B32E@redhat.com> (raw)
In-Reply-To: <20201007001814.GA5138@fieldses.org>
On 6 Oct 2020, at 20:18, J. Bruce Fields wrote:
> On Tue, Oct 06, 2020 at 05:46:11PM -0400, Olga Kornievskaia wrote:
>> On Tue, Oct 6, 2020 at 3:38 PM Benjamin Coddington
>> <bcodding@redhat.com> wrote:
>>>
>>> On 6 Oct 2020, at 11:13, J. Bruce Fields wrote:
>>>
>>>> NFSv4.1+ differs from earlier versions in that it always performs
>>>> trunking discovery that results in mounts to the same server
>>>> sharing a
>>>> TCP connection.
>>>>
>>>> It turns out this results in performance regressions for some
>>>> users;
>>>> apparently the workload on one mount interferes with performance of
>>>> another mount, and they were previously able to work around the
>>>> problem
>>>> by using different server IP addresses for the different mounts.
>>>>
>>>> Am I overlooking some hack that would reenable the previous
>>>> behavior?
>>>> Or would people be averse to an "-o noshareconn" option?
>>>
>>> I suppose you could just toggle the nfs4_unique_id parameter. This
>>> seems to
>>> work:
>>>
>>> flock /sys/module/nfs/parameters/nfs4_unique_id bash -c
>>> "OLD_ID=\$(cat
>>> /sys/module/nfs/parameters/nfs4_unique_id); echo imalittleteapot >
>>> /sys/module/nfs/parameters/nfs4_unique_id; mount -ov4,sec=sys
>>> 10.0.1.200:/exports /mnt/fedora2; echo \$OLD_ID >
>>> /sys/module/nfs/parameters/nfs4_unique_id"
>>>
>>> I'm trying to think of a reason why this is a bad idea, and not
>>> coming
>>> up
>>> with any. Can we support users that have already found this
>>> solution?
>>>
>>
>> What about reboot recovery? How will each mount recover its own state
>> (and present the same identifier it used before). Client only keeps
>> track of one?
>
> Looks like nfs4_init_{non}uniform_client_string() stores it in
> cl_owner_id, and I was thinking that meant cl_owner_id would be used
> from then on....
>
> But actually, I think it may run that again on recovery, yes, so I bet
> changing the nfs4_unique_id parameter midway like this could cause
> bugs
> on recovery.
Ah, that's what I thought as well. Thanks for looking closer Olga!
I don't see why we couldn't store it for the duration of the mount, and
doing so would fix reboot recovery when the uniquifier is changed after
a
mount.
Ben
next prev parent reply other threads:[~2020-10-07 11:27 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-06 15:13 unsharing tcp connections from different NFS mounts J. Bruce Fields
2020-10-06 15:20 ` Chuck Lever
2020-10-06 15:22 ` Bruce Fields
2020-10-06 17:07 ` Tom Talpey
2020-10-06 19:30 ` Bruce Fields
[not found] ` <CAGrwUG5_KeRVR8chcA8=3FSeii2+4c8FbuE=CSGAtYVYqV4kLg@mail.gmail.com>
2020-10-07 14:08 ` Tom Talpey
2020-10-06 19:36 ` Benjamin Coddington
2020-10-06 21:46 ` Olga Kornievskaia
2020-10-07 0:18 ` J. Bruce Fields
2020-10-07 11:27 ` Benjamin Coddington [this message]
2020-10-07 12:55 ` Benjamin Coddington
2020-10-07 13:45 ` Chuck Lever
2020-10-07 14:05 ` Bruce Fields
2020-10-07 14:15 ` Chuck Lever
2020-10-07 16:05 ` Bruce Fields
2020-10-07 16:44 ` Trond Myklebust
2020-10-07 17:15 ` Bruce Fields
2020-10-07 17:29 ` Trond Myklebust
2020-10-07 18:05 ` bfields
2020-10-07 19:11 ` Trond Myklebust
2020-10-07 20:29 ` bfields
2020-10-07 18:04 ` Benjamin Coddington
2020-10-07 18:19 ` Trond Myklebust
2020-10-07 16:50 ` Trond Myklebust
2021-01-19 22:22 ` bfields
2021-01-19 23:09 ` Trond Myklebust
2021-01-20 15:07 ` bfields
2021-05-03 20:09 ` bfields
2021-05-04 2:08 ` NeilBrown
2021-05-04 13:27 ` Tom Talpey
2021-05-04 14:27 ` Trond Myklebust
2021-05-04 16:51 ` bfields
2021-05-04 21:32 ` Daire Byrne
2021-05-04 21:48 ` Trond Myklebust
2021-05-05 12:53 ` Daire Byrne
2021-01-20 15:58 ` Chuck Lever
2020-10-07 13:56 ` Patrick Goetz
2020-10-07 16:28 ` Igor Ostrovsky
2020-10-07 16:30 ` Benjamin Coddington
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