* Re: [f2fs-dev] [PATCH] f2fs: fix double count on issued discard commands
@ 2017-09-12 4:34 ` Daeho Jeong
0 siblings, 0 replies; 16+ messages in thread
From: Daeho Jeong @ 2017-09-12 4:34 UTC (permalink / raw)
To: Jaegeuk Kim; +Cc: linux-fsdevel, linux-kernel, linux-f2fs-devel
> Yeah, that's exactly like what I made a mistake before.
> I should have mentioned that earlier. :)
Or I think the previous code which used "iter++" might be right.
You might just want to check the fixed number of small discards, DISCARD_ISSUE_RATE,
when issue_cond is "true".
Anyways, I have another question about this function.
How about just issuing, not checking whether it is idle, the fixed number of small
discards, DISCARD_ISSUE_RATE, when issue_cond is "true".
Actually, the discard commands will be issued as "asynchronous" requests,
which has a low priority in the I/O scheduler,
so the performance degradation of other threads by doing this will not be much severe,
but we can make the performance of the storage device better even if there is no idle.
I am just worried about the storage device I/O performance gets worse
under I/O intensive senario where there is no idle
Thanks,
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix double count on issued discard commands
2017-09-12 4:34 ` Daeho Jeong
(?)
@ 2017-09-12 17:11 ` Jaegeuk Kim
-1 siblings, 0 replies; 16+ messages in thread
From: Jaegeuk Kim @ 2017-09-12 17:11 UTC (permalink / raw)
To: Daeho Jeong; +Cc: linux-fsdevel, linux-kernel, linux-f2fs-devel
On 09/12, Daeho Jeong wrote:
> > Yeah, that's exactly like what I made a mistake before.
> > I should have mentioned that earlier. :)
>
> Or I think the previous code which used "iter++" might be right.
> You might just want to check the fixed number of small discards, DISCARD_ISSUE_RATE,
> when issue_cond is "true".
>
> Anyways, I have another question about this function.
> How about just issuing, not checking whether it is idle, the fixed number of small
> discards, DISCARD_ISSUE_RATE, when issue_cond is "true".
> Actually, the discard commands will be issued as "asynchronous" requests,
> which has a low priority in the I/O scheduler,
> so the performance degradation of other threads by doing this will not be much severe,
> but we can make the performance of the storage device better even if there is no idle.
I don't think I/O scheduler can efficiently prioritize discard commands and user
requests. The proper way that we can do would be waiting for idle time at this
moment.
Thanks,
>
> I am just worried about the storage device I/O performance gets worse
> under I/O intensive senario where there is no idle
>
> Thanks,
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [PATCH] f2fs: fix double count on issued discard commands
@ 2017-09-12 17:11 ` Jaegeuk Kim
0 siblings, 0 replies; 16+ messages in thread
From: Jaegeuk Kim @ 2017-09-12 17:11 UTC (permalink / raw)
To: Daeho Jeong; +Cc: linux-fsdevel, linux-kernel, linux-f2fs-devel
On 09/12, Daeho Jeong wrote:
> > Yeah, that's exactly like what I made a mistake before.
> > I should have mentioned that earlier. :)
>
> Or I think the previous code which used "iter++" might be right.
> You might just want to check the fixed number of small discards, DISCARD_ISSUE_RATE,
> when issue_cond is "true".
>
> Anyways, I have another question about this function.
> How about just issuing, not checking whether it is idle, the fixed number of small
> discards, DISCARD_ISSUE_RATE, when issue_cond is "true".
> Actually, the discard commands will be issued as "asynchronous" requests,
> which has a low priority in the I/O scheduler,
> so the performance degradation of other threads by doing this will not be much severe,
> but we can make the performance of the storage device better even if there is no idle.
I don't think I/O scheduler can efficiently prioritize discard commands and user
requests. The proper way that we can do would be waiting for idle time at this
moment.
Thanks,
>
> I am just worried about the storage device I/O performance gets worse
> under I/O intensive senario where there is no idle
>
> Thanks,
------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix double count on issued discard commands
@ 2017-09-12 17:11 ` Jaegeuk Kim
0 siblings, 0 replies; 16+ messages in thread
From: Jaegeuk Kim @ 2017-09-12 17:11 UTC (permalink / raw)
To: Daeho Jeong; +Cc: linux-fsdevel, linux-kernel, linux-f2fs-devel
On 09/12, Daeho Jeong wrote:
> > Yeah,�that's�exactly�like�what�I�made�a�mistake�before.
> > I�should�have�mentioned�that�earlier.�:)
>
> Or I think the previous code which used "iter++" might be right.
> You might just want to check the fixed number of small discards, DISCARD_ISSUE_RATE,
> when issue_cond is "true".
>
> Anyways, I have another question about this function.
> How about just issuing, not checking whether it is idle, the fixed number of small
> discards, DISCARD_ISSUE_RATE, when issue_cond is "true".
> Actually, the discard commands will be issued as "asynchronous" requests,
> which has a low priority in the I/O scheduler,
> so the performance degradation of other threads by doing this will not be much severe,
> but we can make the performance of the storage device better even if there is no idle.
I don't think I/O scheduler can efficiently prioritize discard commands and user
requests. The proper way that we can do would be waiting for idle time at this
moment.
Thanks,
>
> I am just worried about the storage device I/O performance gets worse
> under I/O intensive senario where there is no idle
>
> Thanks,
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix double count on issued discard commands
2017-09-12 4:34 ` Daeho Jeong
(?)
@ 2017-09-13 7:13 ` Chao Yu
-1 siblings, 0 replies; 16+ messages in thread
From: Chao Yu @ 2017-09-13 7:13 UTC (permalink / raw)
To: daeho.jeong, Jaegeuk Kim; +Cc: linux-fsdevel, linux-kernel, linux-f2fs-devel
On 2017/9/12 12:34, Daeho Jeong wrote:
>> Yeah, that's exactly like what I made a mistake before.
>> I should have mentioned that earlier. :)
>
> Or I think the previous code which used "iter++" might be right.
> You might just want to check the fixed number of small discards, DISCARD_ISSUE_RATE,
> when issue_cond is "true".
>
> Anyways, I have another question about this function.
> How about just issuing, not checking whether it is idle, the fixed number of small
> discards, DISCARD_ISSUE_RATE, when issue_cond is "true".
> Actually, the discard commands will be issued as "asynchronous" requests,
> which has a low priority in the I/O scheduler,
> so the performance degradation of other threads by doing this will not be much severe,
> but we can make the performance of the storage device better even if there is no idle.
Actually, we didn't change priority of discard command, so that it is still
synchronous IO for I/O scheduler, hence I/O interference will still exist if we
try to issue discard without IO aware ability.
Of course we can change the priority of discard command to lower, but potential
issue is that with ROW I/O scheduler in kernel or FTL, async I/O will handle
very slowly in heavy load scenario, if we are going to trigger sync write IO in
place in where we're doing async discard, we will face long latency.
Still I think it is worth to build the ability to issue async discard as a part
of discard policy and later we can adjust policy based on different scenario.
Thanks,
>
> I am just worried about the storage device I/O performance gets worse
> under I/O intensive senario where there is no idle
>
> Thanks,
>
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [PATCH] f2fs: fix double count on issued discard commands
@ 2017-09-13 7:13 ` Chao Yu
0 siblings, 0 replies; 16+ messages in thread
From: Chao Yu @ 2017-09-13 7:13 UTC (permalink / raw)
To: daeho.jeong, Jaegeuk Kim; +Cc: linux-fsdevel, linux-kernel, linux-f2fs-devel
On 2017/9/12 12:34, Daeho Jeong wrote:
>> Yeah, that's exactly like what I made a mistake before.
>> I should have mentioned that earlier. :)
>
> Or I think the previous code which used "iter++" might be right.
> You might just want to check the fixed number of small discards, DISCARD_ISSUE_RATE,
> when issue_cond is "true".
>
> Anyways, I have another question about this function.
> How about just issuing, not checking whether it is idle, the fixed number of small
> discards, DISCARD_ISSUE_RATE, when issue_cond is "true".
> Actually, the discard commands will be issued as "asynchronous" requests,
> which has a low priority in the I/O scheduler,
> so the performance degradation of other threads by doing this will not be much severe,
> but we can make the performance of the storage device better even if there is no idle.
Actually, we didn't change priority of discard command, so that it is still
synchronous IO for I/O scheduler, hence I/O interference will still exist if we
try to issue discard without IO aware ability.
Of course we can change the priority of discard command to lower, but potential
issue is that with ROW I/O scheduler in kernel or FTL, async I/O will handle
very slowly in heavy load scenario, if we are going to trigger sync write IO in
place in where we're doing async discard, we will face long latency.
Still I think it is worth to build the ability to issue async discard as a part
of discard policy and later we can adjust policy based on different scenario.
Thanks,
>
> I am just worried about the storage device I/O performance gets worse
> under I/O intensive senario where there is no idle
>
> Thanks,
>
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>
------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix double count on issued discard commands
@ 2017-09-13 7:13 ` Chao Yu
0 siblings, 0 replies; 16+ messages in thread
From: Chao Yu @ 2017-09-13 7:13 UTC (permalink / raw)
To: daeho.jeong, Jaegeuk Kim; +Cc: linux-fsdevel, linux-kernel, linux-f2fs-devel
On 2017/9/12 12:34, Daeho Jeong wrote:
>> Yeah, that's exactly like what I made a mistake before.
>> I should have mentioned that earlier. :)
>
> Or I think the previous code which used "iter++" might be right.
> You might just want to check the fixed number of small discards, DISCARD_ISSUE_RATE,
> when issue_cond is "true".
>
> Anyways, I have another question about this function.
> How about just issuing, not checking whether it is idle, the fixed number of small
> discards, DISCARD_ISSUE_RATE, when issue_cond is "true".
> Actually, the discard commands will be issued as "asynchronous" requests,
> which has a low priority in the I/O scheduler,
> so the performance degradation of other threads by doing this will not be much severe,
> but we can make the performance of the storage device better even if there is no idle.
Actually, we didn't change priority of discard command, so that it is still
synchronous IO for I/O scheduler, hence I/O interference will still exist if we
try to issue discard without IO aware ability.
Of course we can change the priority of discard command to lower, but potential
issue is that with ROW I/O scheduler in kernel or FTL, async I/O will handle
very slowly in heavy load scenario, if we are going to trigger sync write IO in
place in where we're doing async discard, we will face long latency.
Still I think it is worth to build the ability to issue async discard as a part
of discard policy and later we can adjust policy based on different scenario.
Thanks,
>
> I am just worried about the storage device I/O performance gets worse
> under I/O intensive senario where there is no idle
>
> Thanks,
>
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>
^ permalink raw reply [flat|nested] 16+ messages in thread
[parent not found: <CGME20170912042935epcas1p4630737028cc7b9536a0c688c92084e84@epcms1p8>]
* Re: [f2fs-dev] [PATCH] f2fs: fix double count on issued discard commands
[not found] ` <CGME20170912042935epcas1p4630737028cc7b9536a0c688c92084e84@epcms1p8>
@ 2017-09-13 8:48 ` Daeho Jeong
0 siblings, 0 replies; 16+ messages in thread
From: Daeho Jeong @ 2017-09-13 8:48 UTC (permalink / raw)
To: linux-fsdevel, linux-kernel, linux-f2fs-devel
> Actually, we didn't change priority of discard command, so that it is still
> synchronous IO for I/O scheduler, hence I/O interference will still exist if we
> try to issue discard without IO aware ability.
> Of course we can change the priority of discard command to lower, but potential
> issue is that with ROW I/O scheduler in kernel or FTL, async I/O will handle
> very slowly in heavy load scenario, if we are going to trigger sync write IO in
> place in where we're doing async discard, we will face long latency.
> Still I think it is worth to build the ability to issue async discard as a part
> of discard policy and later we can adjust policy based on different scenario.
> Thanks,
Oh, I see.
f2fs is sending discard requests as "sync" requests, I didn't know that.
Right, I just though in case of CFQ I/O scheduler, but f2fs has to consider the other
schedulers, but CFQ.
Thanks, :)
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix double count on issued discard commands
@ 2017-09-13 8:48 ` Daeho Jeong
0 siblings, 0 replies; 16+ messages in thread
From: Daeho Jeong @ 2017-09-13 8:48 UTC (permalink / raw)
To: linux-fsdevel, linux-kernel, linux-f2fs-devel
> Actually, we didn't change priority of discard command, so that it is still
> synchronous IO for I/O scheduler, hence I/O interference will still exist if we
> try to issue discard without IO aware ability.
> Of course we can change the priority of discard command to lower, but potential
> issue is that with ROW I/O scheduler in kernel or FTL, async I/O will handle
> very slowly in heavy load scenario, if we are going to trigger sync write IO in
> place in where we're doing async discard, we will face long latency.
> Still I think it is worth to build the ability to issue async discard as a part
> of discard policy and later we can adjust policy based on different scenario.
> Thanks,
Oh, I see.
f2fs is sending discard requests as "sync" requests, I didn't know that.
Right, I just though in case of CFQ I/O scheduler, but f2fs has to consider the other
schedulers, but CFQ.
Thanks, :)
^ permalink raw reply [flat|nested] 16+ messages in thread