Re: wb-buf-throttle feedback

[Ritesh Raj Sarraf <rrs@researchut.com>]

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Hello Jens,


On Fri, 2016-09-09 at 14:19 -0600, Jens Axboe wrote:
> > What drive is hosting the system and kernel build? I think the current
> > branch isn't aggressive enough on SATA style QD=32 devices with write
> > back caching, so if that's what you are running, it'd be great if you
> > could try a patch or two so we can improve this situation for you.
> >
> > The v4.7 branch is outdated. Let me spin a new one, that's probably the
> > best way to start.
> 

The drive is:

Sep 10 18:19:32 chutzpah kernel: ata1: SATA link up 6.0 Gbps (SStatus 133
SControl 300)
Sep 10 18:19:32 chutzpah kernel: ata1.00: ATA-9: HGST HTS725050A7E630, GH2OA910,
max UDMA/133
Sep 10 18:19:32 chutzpah kernel: ata1.00: 976773168 sectors, multi 16: LBA48 NCQ
(depth 31/32), AA
Sep 10 18:19:32 chutzpah kernel: ata1.00: configured for UDMA/133
Sep 10 18:19:32 chutzpah kernel: scsi 0:0:0:0: Direct-Access     ATA      HGST
HTS725050A7 A910 PQ: 0 ANSI: 5
Sep 10 18:19:32 chutzpah kernel: sd 0:0:0:0: [sda] 976773168 512-byte logical
blocks: (500 GB/466 GiB)
Sep 10 18:19:32 chutzpah kernel: sd 0:0:0:0: [sda] 4096-byte physical blocks
Sep 10 18:19:32 chutzpah kernel: sd 0:0:0:0: [sda] Write Protect is off
Sep 10 18:19:32 chutzpah kernel: sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
Sep 10 18:19:32 chutzpah kernel: sd 0:0:0:0: [sda] Write cache: enabled, read
cache: enabled, doesn't support DPO or FUA
Sep 10 18:19:32 chutzpah kernel: usb 1-4: new full-speed USB device number 2
using xhci_hcd
Sep 10 18:19:32 chutzpah kernel:  sda: sda1 sda2 sda3 sda4 < sda5 >
Sep 10 18:19:32 chutzpah kernel: sd 0:0:0:0: [sda] Attached SCSI disk


> The 4.7 branch has now been updated, it's fully uptodate with the
> current 4.8 based branch. Would be great if you could try that. If you
> still see slowdowns, try and change RWB_DEF_DEPTH. It's currently at 16,
> scale it down to 4 or something like that.


I pulled in your changes from the axboe/wb-buf-throttle-v4.7 branch.

I can confirm now that, with these changes, the machine is very well responsive.
I tried both, the kernel build and the dd tests. Both of them worked fine.

Thank you very much.

Ritesh

- -- 
Ritesh Raj Sarraf
RESEARCHUT - http://www.researchut.com
"Necessity is the mother of invention."
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