From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCHv2 8/8] zsmalloc: register a shrinker to trigger auto-compaction
Date: Thu, 18 Jun 2015 12:58:20 +0900 [thread overview]
Message-ID: <20150618035820.GE3422@swordfish> (raw)
In-Reply-To: <20150618033922.GB2370@bgram>
On (06/18/15 12:39), Minchan Kim wrote:
[..]
> > ah, I see.
> > it doesn't hold the lock `until all the pages are done`. it holds it
> > as long as zs_can_compact() returns > 0. hm, I'm not entirely sure that
> > this patch set has increased the locking time (in average).
>
> I see your point. Sorry for the consusing.
> My point is not average but max time. I bet your patch will increase
> it and it will affect others who want to allocate zspage in parallel on
> another CPU.
makes sense.
[..]
> > > Yes, it's not easy and I believe a few artificial testing are not enough
> > > to prove no regression but we don't have any choice.
> > > Actually, I think this patchset does make sense. Although it might have
> > > a problem on situation heavy memory pressure by lacking of fragment space,
> >
> >
> > I tested exactly this scenario yesterday (and sent an email). We leave `no holes'
> > in classes only in ~1.35% of cases. so, no, this argument is not valid. we preserve
> > fragmentation.
>
> Thanks, Sergey.
>
> I want to test by myself to simulate worst case scenario to make to use up
> reserved memory by zram. For it, please fix below first and resubmit, please.
>
> 1. doesn't hold lock until class compation is done.
> It could prevent another allocation on another CPU.
> I want to make worst case scenario and it needs it.
>
> 2. No touch ZS_ALMOST_FULL waterline. It can put more zspages
> in ZS_ALMOST_FULL list so it couldn't be selected by migration
> source.
>
> With new patchset, I want to watch min(free_pages of the system),
> zram.max_used_pages, testing time and so on.
>
> Really sorry for bothering you, Sergey but I think it's important
> feature on zram so I want to be careful because risk management is
> my role.
ok. will take a day or two to gather new numbers.
-ss
WARNING: multiple messages have this Message-ID (diff)
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCHv2 8/8] zsmalloc: register a shrinker to trigger auto-compaction
Date: Thu, 18 Jun 2015 12:58:20 +0900 [thread overview]
Message-ID: <20150618035820.GE3422@swordfish> (raw)
In-Reply-To: <20150618033922.GB2370@bgram>
On (06/18/15 12:39), Minchan Kim wrote:
[..]
> > ah, I see.
> > it doesn't hold the lock `until all the pages are done`. it holds it
> > as long as zs_can_compact() returns > 0. hm, I'm not entirely sure that
> > this patch set has increased the locking time (in average).
>
> I see your point. Sorry for the consusing.
> My point is not average but max time. I bet your patch will increase
> it and it will affect others who want to allocate zspage in parallel on
> another CPU.
makes sense.
[..]
> > > Yes, it's not easy and I believe a few artificial testing are not enough
> > > to prove no regression but we don't have any choice.
> > > Actually, I think this patchset does make sense. Although it might have
> > > a problem on situation heavy memory pressure by lacking of fragment space,
> >
> >
> > I tested exactly this scenario yesterday (and sent an email). We leave `no holes'
> > in classes only in ~1.35% of cases. so, no, this argument is not valid. we preserve
> > fragmentation.
>
> Thanks, Sergey.
>
> I want to test by myself to simulate worst case scenario to make to use up
> reserved memory by zram. For it, please fix below first and resubmit, please.
>
> 1. doesn't hold lock until class compation is done.
> It could prevent another allocation on another CPU.
> I want to make worst case scenario and it needs it.
>
> 2. No touch ZS_ALMOST_FULL waterline. It can put more zspages
> in ZS_ALMOST_FULL list so it couldn't be selected by migration
> source.
>
> With new patchset, I want to watch min(free_pages of the system),
> zram.max_used_pages, testing time and so on.
>
> Really sorry for bothering you, Sergey but I think it's important
> feature on zram so I want to be careful because risk management is
> my role.
ok. will take a day or two to gather new numbers.
-ss
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next prev parent reply other threads:[~2015-06-18 3:58 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-05 12:03 [RFC][PATCHv2 0/8] introduce automatic pool compaction Sergey Senozhatsky
2015-06-05 12:03 ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 1/8] zsmalloc: drop unused variable `nr_to_migrate' Sergey Senozhatsky
2015-06-05 12:03 ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 2/8] zsmalloc: partial page ordering within a fullness_list Sergey Senozhatsky
2015-06-05 12:03 ` Sergey Senozhatsky
2015-06-16 13:19 ` Minchan Kim
2015-06-16 13:19 ` Minchan Kim
2015-06-16 14:30 ` Sergey Senozhatsky
2015-06-16 14:30 ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 3/8] zsmalloc: lower ZS_ALMOST_FULL waterline Sergey Senozhatsky
2015-06-05 12:03 ` Sergey Senozhatsky
2015-06-16 13:37 ` Minchan Kim
2015-06-16 13:37 ` Minchan Kim
2015-06-16 14:35 ` Sergey Senozhatsky
2015-06-16 14:35 ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 4/8] zsmalloc: always keep per-class stats Sergey Senozhatsky
2015-06-05 12:03 ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 5/8] zsmalloc: introduce zs_can_compact() function Sergey Senozhatsky
2015-06-05 12:03 ` Sergey Senozhatsky
2015-06-16 14:19 ` Minchan Kim
2015-06-16 14:19 ` Minchan Kim
2015-06-16 14:41 ` Sergey Senozhatsky
2015-06-16 14:41 ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 6/8] zsmalloc: cosmetic compaction code adjustments Sergey Senozhatsky
2015-06-05 12:03 ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 7/8] zsmalloc/zram: move `num_migrated' to zs_pool Sergey Senozhatsky
2015-06-05 12:03 ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 8/8] zsmalloc: register a shrinker to trigger auto-compaction Sergey Senozhatsky
2015-06-05 12:03 ` Sergey Senozhatsky
2015-06-16 14:47 ` Minchan Kim
2015-06-16 14:47 ` Minchan Kim
2015-06-16 15:45 ` Sergey Senozhatsky
2015-06-16 15:45 ` Sergey Senozhatsky
2015-06-18 1:50 ` Minchan Kim
2015-06-18 1:50 ` Minchan Kim
2015-06-18 2:41 ` Sergey Senozhatsky
2015-06-18 2:41 ` Sergey Senozhatsky
2015-06-18 3:01 ` Sergey Senozhatsky
2015-06-18 3:01 ` Sergey Senozhatsky
2015-06-18 3:46 ` Minchan Kim
2015-06-18 3:46 ` Minchan Kim
2015-06-18 3:39 ` Minchan Kim
2015-06-18 3:39 ` Minchan Kim
2015-06-18 3:58 ` Sergey Senozhatsky [this message]
2015-06-18 3:58 ` Sergey Senozhatsky
2015-06-17 7:11 ` Sergey Senozhatsky
2015-06-17 7:11 ` Sergey Senozhatsky
2015-06-10 0:04 ` [RFC][PATCHv2 0/8] introduce automatic pool compaction Minchan Kim
2015-06-10 0:04 ` Minchan Kim
2015-06-10 0:07 ` Sergey Senozhatsky
2015-06-10 0:07 ` Sergey Senozhatsky
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