Re: [PATCH BUGFIX/IMPROVEMENT 0/2] block, bfq: two pending patches

[Jens Axboe]

On 1/13/18 4:05 AM, Paolo Valente wrote:
> Hi Jens,
> here are again the two pending patches you asked me to resend [1]. One
> of them, fixing read-starvation problems, was accompanied by a cover
> letter. I'm pasting the content of that cover letter below.
> 
> The patch addresses (serious) starvation problems caused by
> request-tag exhaustion, as explained in more detail in the commit
> message. I started from the solution in the function
> kyber_limit_depth, but then I had to define more articulate limits, to
> counter starvation also in cases not covered in kyber_limit_depth.
> If this solution proves to be effective, I'm willing to port it
> somehow to the other schedulers.

It's something we've been doing in the old request layer for tagging for
a long time (more than a decade), so a generic (and fast) solution that
covers all cases for blk-mq-tag would indeed be great.

For now, I have applied these for 4.16, thanks.

-- 
Jens Axboe

Re: [PATCH BUGFIX/IMPROVEMENT 0/2] block, bfq: two pending patches

[Paolo Valente]

> Il giorno 13 gen 2018, alle ore 12:05, Paolo Valente 
>  ha scritto:
> 
> Hi Jens,
> here are again the two pending patches you asked me to resend [1]. One
> of them, fixing read-starvation problems, was accompanied by a cover
> letter. I'm pasting the content of that cover letter below.
> 
> The patch addresses (serious) starvation problems caused by
> request-tag exhaustion, as explained in more detail in the commit
> message. I started from the solution in the function
> kyber_limit_depth, but then I had to define more articulate limits, to
> counter starvation also in cases not covered in kyber_limit_depth.
> If this solution proves to be effective, I'm willing to port it
> somehow to the other schedulers.
> 

Hi Jens,
have had to time to check these patches?  Sorry for pushing, but I
guess 4.16 is getting closer, and these patches are performance
critical; especially the first, which solves a starvation problem.

Thanks,
Paolo

> Thanks,
> Paolo
> 
> [1] https://www.spinics.net/lists/linux-block/msg21586.html
> 
> Paolo Valente (2):
>  block, bfq: limit tags for writes and async I/O
>  block, bfq: limit sectors served with interactive weight raising
> 
> block/bfq-iosched.c | 158 +---
> block/bfq-iosched.h |  17 ++
> block/bfq-wf2q.c|   3 +
> 3 files changed, 169 insertions(+), 9 deletions(-)
> 
> --
> 2.15.1

Re: [PATCH BUGFIX/IMPROVEMENT 0/2] block, bfq: two pending patches

[Oleksandr Natalenko]

Hi.

13.01.2018 12:05, Paolo Valente wrote:

Hi Jens,
here are again the two pending patches you asked me to resend [1]. One
of them, fixing read-starvation problems, was accompanied by a cover
letter. I'm pasting the content of that cover letter below.

The patch addresses (serious) starvation problems caused by
request-tag exhaustion, as explained in more detail in the commit
message. I started from the solution in the function
kyber_limit_depth, but then I had to define more articulate limits, to
counter starvation also in cases not covered in kyber_limit_depth.
If this solution proves to be effective, I'm willing to port it
somehow to the other schedulers.

Thanks,
Paolo

[1] https://www.spinics.net/lists/linux-block/msg21586.html

Paolo Valente (2):
  block, bfq: limit tags for writes and async I/O
  block, bfq: limit sectors served with interactive weight raising

 block/bfq-iosched.c | 158 
+---

 block/bfq-iosched.h |  17 ++
 block/bfq-wf2q.c|   3 +
 3 files changed, 169 insertions(+), 9 deletions(-)

--
2.15.1


I'm running the system with these patches since the end of December, so 
with regard to stability and visible smoke:


Tested-by: Oleksandr Natalenko 

for both of them.

Many thanks, Paolo!

[PATCH BUGFIX/IMPROVEMENT 0/2] block, bfq: two pending patches

[Paolo Valente]

Hi Jens,
here are again the two pending patches you asked me to resend [1]. One
of them, fixing read-starvation problems, was accompanied by a cover
letter. I'm pasting the content of that cover letter below.

The patch addresses (serious) starvation problems caused by
request-tag exhaustion, as explained in more detail in the commit
message. I started from the solution in the function
kyber_limit_depth, but then I had to define more articulate limits, to
counter starvation also in cases not covered in kyber_limit_depth.
If this solution proves to be effective, I'm willing to port it
somehow to the other schedulers.

Thanks,
Paolo

[1] https://www.spinics.net/lists/linux-block/msg21586.html

Paolo Valente (2):
  block, bfq: limit tags for writes and async I/O
  block, bfq: limit sectors served with interactive weight raising

 block/bfq-iosched.c | 158 +---
 block/bfq-iosched.h |  17 ++
 block/bfq-wf2q.c|   3 +
 3 files changed, 169 insertions(+), 9 deletions(-)

--
2.15.1