From: Miklos Szeredi <mszeredi@redhat.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"Venegas Munoz,
Jose Carlos" <jose.carlos.venegas.munoz@intel.com>,
"cdupontd@redhat.com" <cdupontd@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
virtio-fs-list <virtio-fs@redhat.com>,
"Shinde, Archana M" <archana.m.shinde@intel.com>
Subject: Re: [Virtio-fs] virtiofs vs 9p performance(Re: tools/virtiofs: Multi threading seems to hurt performance)
Date: Tue, 29 Sep 2020 16:54:15 +0200 [thread overview]
Message-ID: <CAOssrKd8RAQ+D0o8O9HJND5skG0-wZhucz2R9sH-CC_4cASH3w@mail.gmail.com> (raw)
In-Reply-To: <20200929140136.GD220516@redhat.com>
On Tue, Sep 29, 2020 at 4:01 PM Vivek Goyal <vgoyal@redhat.com> wrote:
>
> On Tue, Sep 29, 2020 at 03:49:04PM +0200, Miklos Szeredi wrote:
> > On Tue, Sep 29, 2020 at 3:18 PM Vivek Goyal <vgoyal@redhat.com> wrote:
> >
> > > - virtiofs cache=none mode is faster than cache=auto mode for this
> > > workload.
> >
> > Not sure why. One cause could be that readahead is not perfect at
> > detecting the random pattern. Could we compare total I/O on the
> > server vs. total I/O by fio?
>
> Hi Miklos,
>
> I will instrument virtiosd code to figure out total I/O.
>
> One more potential issue I am staring at is refreshing the attrs on
> READ if fc->auto_inval_data is set.
>
> fuse_cache_read_iter() {
> /*
> * In auto invalidate mode, always update attributes on read.
> * Otherwise, only update if we attempt to read past EOF (to ensure
> * i_size is up to date).
> */
> if (fc->auto_inval_data ||
> (iocb->ki_pos + iov_iter_count(to) > i_size_read(inode))) {
> int err;
> err = fuse_update_attributes(inode, iocb->ki_filp);
> if (err)
> return err;
> }
> }
>
> Given this is a mixed READ/WRITE workload, every WRITE will invalidate
> attrs. And next READ will first do GETATTR() from server (and potentially
> invalidate page cache) before doing READ.
>
> This sounds suboptimal especially from the point of view of WRITEs
> done by this client itself. I mean if another client has modified
> the file, then doing GETATTR after a second makes sense. But there
> should be some optimization to make sure our own WRITEs don't end
> up doing GETATTR and invalidate page cache (because cache contents
> are still valid).
Yeah, that sucks.
> I disabled ->auto_invalid_data and that seemed to result in 8-10%
> gain in performance for this workload.
Need to wrap my head around these caching issues.
Thanks,
Miklos
next prev parent reply other threads:[~2020-09-29 14:55 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-18 21:34 tools/virtiofs: Multi threading seems to hurt performance Vivek Goyal
2020-09-21 8:39 ` Stefan Hajnoczi
2020-09-21 13:39 ` Vivek Goyal
2020-09-21 16:57 ` Stefan Hajnoczi
2020-09-21 8:50 ` Dr. David Alan Gilbert
2020-09-21 13:35 ` Vivek Goyal
2020-09-21 14:08 ` Daniel P. Berrangé
2020-09-21 15:32 ` Dr. David Alan Gilbert
2020-09-22 10:25 ` Dr. David Alan Gilbert
2020-09-22 17:47 ` Vivek Goyal
2020-09-24 21:33 ` Venegas Munoz, Jose Carlos
2020-09-24 22:10 ` virtiofs vs 9p performance(Re: tools/virtiofs: Multi threading seems to hurt performance) Vivek Goyal
2020-09-25 8:06 ` virtiofs vs 9p performance Christian Schoenebeck
2020-09-25 13:13 ` Vivek Goyal
2020-09-25 15:47 ` Christian Schoenebeck
2021-02-19 16:08 ` Can not set high msize with virtio-9p (Was: Re: virtiofs vs 9p performance) Vivek Goyal
2021-02-19 17:33 ` Christian Schoenebeck
2021-02-19 19:01 ` Vivek Goyal
2021-02-20 15:38 ` Christian Schoenebeck
2021-02-22 12:18 ` Greg Kurz
2021-02-22 15:08 ` Christian Schoenebeck
2021-02-22 17:11 ` Greg Kurz
2021-02-23 13:39 ` Christian Schoenebeck
2021-02-23 14:07 ` Michael S. Tsirkin
2021-02-24 15:16 ` Christian Schoenebeck
2021-02-24 15:43 ` Dominique Martinet
2021-02-26 13:49 ` Christian Schoenebeck
2021-02-27 0:03 ` Dominique Martinet
2021-03-03 14:04 ` Christian Schoenebeck
2021-03-03 14:50 ` Dominique Martinet
2021-03-05 14:57 ` Christian Schoenebeck
2020-09-25 12:41 ` virtiofs vs 9p performance(Re: tools/virtiofs: Multi threading seems to hurt performance) Dr. David Alan Gilbert
2020-09-25 13:04 ` Christian Schoenebeck
2020-09-25 13:05 ` Dr. David Alan Gilbert
2020-09-25 16:05 ` Christian Schoenebeck
2020-09-25 16:33 ` Christian Schoenebeck
2020-09-25 18:51 ` Dr. David Alan Gilbert
2020-09-27 12:14 ` Christian Schoenebeck
2020-09-29 13:03 ` Vivek Goyal
2020-09-29 13:28 ` Christian Schoenebeck
2020-09-29 13:49 ` Vivek Goyal
2020-09-29 13:59 ` Christian Schoenebeck
2020-09-29 13:17 ` Vivek Goyal
2020-09-29 13:49 ` [Virtio-fs] " Miklos Szeredi
2020-09-29 14:01 ` Vivek Goyal
2020-09-29 14:54 ` Miklos Szeredi [this message]
2020-09-29 15:28 ` Vivek Goyal
2020-09-25 12:11 ` tools/virtiofs: Multi threading seems to hurt performance Dr. David Alan Gilbert
2020-09-25 13:11 ` Vivek Goyal
2020-09-21 20:16 ` Vivek Goyal
2020-09-22 11:09 ` Dr. David Alan Gilbert
2020-09-22 22:56 ` Vivek Goyal
2020-09-23 12:50 ` [Virtio-fs] " Chirantan Ekbote
2020-09-23 12:59 ` Vivek Goyal
2020-09-25 11:35 ` Dr. David Alan Gilbert
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