multi-threaded raid5

multi-threaded raid5

[stkoupr]

Hi,

We are testing write performance of md raid5 with SSD array and we are 
hitting limit which I understand is caused by writes being handled in 
single thread (md0_raid5 process is eating 100% of 1 CPU core when the 
test is running). I understood that there is some work in progress which 
should make write handling multi-threaded. I'd like to ask about the 
status of this work, is it still in progress or planned?

Regards,
Prema

Re: multi-threaded raid5

[NeilBrown]

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On Tue, 31 Mar 2015 19:17:34 +0200 stkoupr <p.kouril@cra.cz> wrote:

> Hi,
> 
> We are testing write performance of md raid5 with SSD array and we are 
> hitting limit which I understand is caused by writes being handled in 
> single thread (md0_raid5 process is eating 100% of 1 CPU core when the 
> test is running). I understood that there is some work in progress which 
> should make write handling multi-threaded. I'd like to ask about the 
> status of this work, is it still in progress or planned?
> 
> Regards,
> Prema
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See /sys/block/mdXXX/md/group_thread_cnt

Set it to a bigger number, get more threads.

Requires 3.12 or later.

NeilBrown

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Re: multi-threaded raid5

[Thomas Fjellstrom]

On Tue 07 Apr 2015 11:11:57 AM NeilBrown wrote:
> On Tue, 31 Mar 2015 19:17:34 +0200 stkoupr <p.kouril@cra.cz> wrote:
> > Hi,
> > 
> > We are testing write performance of md raid5 with SSD array and we are
> > hitting limit which I understand is caused by writes being handled in
> > single thread (md0_raid5 process is eating 100% of 1 CPU core when the
> > test is running). I understood that there is some work in progress which
> > should make write handling multi-threaded. I'd like to ask about the
> > status of this work, is it still in progress or planned?
> > 
> > Regards,
> > Prema
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> See /sys/block/mdXXX/md/group_thread_cnt
> 
> Set it to a bigger number, get more threads.
> 
> Requires 3.12 or later.

What does it mean when that property is set to 0?

> NeilBrown

-- 
Thomas Fjellstrom
thomas@fjellstrom.ca