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From: Steve French <smfrench@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Shyam Prasad N <nspmangalore@gmail.com>,
	CIFS <linux-cifs@vger.kernel.org>,
	Jeff Layton <jlayton@redhat.com>,
	David Howells <dhowells@redhat.com>
Subject: Re: [PATCH] smb3: add rasize mount parameter to improve performance of readahead
Date: Mon, 26 Apr 2021 21:23:36 -0500	[thread overview]
Message-ID: <CAH2r5muEvEUAMEonGWYvBUp1Xp67eACEVNs3JtR9XKTts7vVPw@mail.gmail.com> (raw)
In-Reply-To: <20210426115457.GJ235567@casper.infradead.org>

On Mon, Apr 26, 2021 at 6:55 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Apr 26, 2021 at 10:22:27AM +0530, Shyam Prasad N wrote:
> > Agree with this. Was experimenting on the similar lines on Friday.
> > Does show good improvements with sequential workload.
> > For random read/write workload, the user can use the default value.
>
> For a random access workload, Linux's readahead shouldn't kick in.
> Do you see a slowdown when using this patch with a random I/O workload?

I see few slowdowns in the 20 or so xfstests I have tried, but the
value of rasize
varies a lot by server type and network type and number of channels.  I don't
have enough data to set rasize well (I have experimented with 4MB to 12MB
but need more data).

In some experiments running 20+ typical xfstests

So far I see really good improvement in multichannel to Azure with setting
rasize to 4 times negotiated read size. But I saw less than a 1% gain though
to a slower Windows server running in a VM (without multichannel).  I
also didn't
see a gain to localhost Samba in the simple examples I tried. I saw
about an 11% gain to a typical Azure share without multichannel. See
some example perf data below. The numbers on right are perf with
rasize set to 4MB,
ie 4 times the negotiated read size, instead of results using defaults
of ra_pages = 1MB rsize (on the left).

generic/001 113s ...  117s
generic/005 35s ...  34s
generic/006 567s ...  503s
generic/010 1s ...  1s
generic/011 620s ...  594s
generic/024 10s ...  10s
generic/028 5s ...  5s
generic/029 2s ...  2s
generic/030 3s ...  2s
generic/036 11s ...  11s
generic/069 7s ...  7s
generic/070 287s ...  270s
generic/080 3s ...  2s
generic/084 6s ...  6s
generic/086 1s ...  1s
generic/095 25s ...  23s
generic/098 1s ...  1s
generic/109 469s ...  328s
generic/117 219s ...  201s
generic/124 21s ...  20s
generic/125 63s ...  62s
generic/130 27s ...  24s
generic/132 24s ...  25s


-- 
Thanks,

Steve

  reply	other threads:[~2021-04-27  2:23 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-24 19:27 [PATCH] smb3: add rasize mount parameter to improve performance of readahead Steve French
2021-04-24 20:08 ` Steve French
2021-04-25  2:09 ` Matthew Wilcox
2021-04-25  2:36   ` Steve French
2021-04-25 16:50     ` Steve French
2021-04-26  4:52       ` Shyam Prasad N
2021-04-26 11:54         ` Matthew Wilcox
2021-04-27  2:23           ` Steve French [this message]
2021-04-30 10:49           ` Shyam Prasad N
2021-04-30 11:59             ` Matthew Wilcox
2021-04-30 12:53               ` Shyam Prasad N
2021-04-30 19:22               ` Steve French
2021-05-01 18:35                 ` Matthew Wilcox
2021-05-01 18:47                   ` Steve French
2021-05-01 18:50                     ` Steve French

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