From: Fox Chen <foxhlchen@gmail.com>
To: Ian Kent <raven@themaw.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Tejun Heo <tj@kernel.org>, Al Viro <viro@zeniv.linux.org.uk>,
Eric Sandeen <sandeen@sandeen.net>,
Brice Goglin <brice.goglin@gmail.com>,
Rick Lindsley <ricklind@linux.vnet.ibm.com>,
David Howells <dhowells@redhat.com>,
Miklos Szeredi <miklos@szeredi.hu>,
Marcelo Tosatti <mtosatti@redhat.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 0/5] kernfs: proposed locking and concurrency improvement
Date: Thu, 13 May 2021 23:37:38 +0800 [thread overview]
Message-ID: <CAC2o3DKvq12CrsgWTNmQmu3iDJ+9tytMdCJepdBjUKN1iUJ0RQ@mail.gmail.com> (raw)
In-Reply-To: <4eae44395ad321d05f47571b58fe3fe2413b6b36.camel@themaw.net>
Hi Ian
On Thu, May 13, 2021 at 10:10 PM Ian Kent <raven@themaw.net> wrote:
>
> On Wed, 2021-05-12 at 16:54 +0800, Fox Chen wrote:
> > On Wed, May 12, 2021 at 4:47 PM Fox Chen <foxhlchen@gmail.com> wrote:
> > >
> > > Hi,
> > >
> > > I ran it on my benchmark (
> > > https://github.com/foxhlchen/sysfs_benchmark).
> > >
> > > machine: aws c5 (Intel Xeon with 96 logical cores)
> > > kernel: v5.12
> > > benchmark: create 96 threads and bind them to each core then run
> > > open+read+close on a sysfs file simultaneously for 1000 times.
> > > result:
> > > Without the patchset, an open+read+close operation takes 550-570
> > > us,
> > > perf shows significant time(>40%) spending on mutex_lock.
> > > After applying it, it takes 410-440 us for that operation and perf
> > > shows only ~4% time on mutex_lock.
> > >
> > > It's weird, I don't see a huge performance boost compared to v2,
> > > even
> >
> > I meant I don't see a huge performance boost here and it's way worse
> > than v2.
> > IIRC, for v2 fastest one only takes 40us
>
> Thanks Fox,
>
> I'll have a look at those reports but this is puzzling.
>
> Perhaps the added overhead of the check if an update is
> needed is taking more than expected and more than just
> taking the lock and being done with it. Then there's
> the v2 series ... I'll see if I can dig out your reports
> on those too.
Apologies, I was mistaken, it's compared to V3, not V2. The previous
benchmark report is here.
https://lore.kernel.org/linux-fsdevel/CAC2o3DKNc=sL2n8291Dpiyb0bRHaX=nd33ogvO_LkJqpBj-YmA@mail.gmail.com/
> >
> >
> > > though there is no mutex problem from the perf report.
> > > I've put console outputs and perf reports on the attachment for
> > > your reference.
>
> Yep, thanks.
> Ian
>
thanks,
fox
next prev parent reply other threads:[~2021-05-13 15:38 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 0:38 [PATCH v4 0/5] kernfs: proposed locking and concurrency improvement Ian Kent
2021-05-12 0:38 ` [PATCH v4 1/5] kernfs: move revalidate to be near lookup Ian Kent
2021-05-12 0:38 ` [PATCH v4 2/5] kernfs: use VFS negative dentry caching Ian Kent
2021-05-12 0:39 ` [PATCH v4 3/5] kernfs: switch kernfs to use an rwsem Ian Kent
2021-05-12 0:39 ` [PATCH v4 4/5] kernfs: use i_lock to protect concurrent inode updates Ian Kent
2021-05-12 0:39 ` [PATCH v4 5/5] kernfs: add kernfs_need_inode_refresh() Ian Kent
2021-05-12 6:21 ` [PATCH v4 0/5] kernfs: proposed locking and concurrency improvement Greg Kroah-Hartman
2021-05-12 7:16 ` Fox Chen
2021-05-12 8:47 ` Fox Chen
2021-05-12 8:54 ` Fox Chen
2021-05-13 14:10 ` Ian Kent
2021-05-13 15:37 ` Fox Chen [this message]
2021-05-14 1:34 ` Ian Kent
2021-05-14 2:34 ` Fox Chen
2021-05-17 1:32 ` Ian Kent
2021-05-18 8:26 ` Fox Chen
2021-05-27 1:23 ` Ian Kent
2021-05-27 6:50 ` Greg Kroah-Hartman
2021-05-28 5:45 ` Ian Kent
2021-05-13 13:50 ` Ian Kent
2021-05-13 15:19 ` Greg Kroah-Hartman
2021-05-14 1:02 ` Ian Kent
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