From: Seth Jennings <sjenning@linux.vnet.ibm.com>
To: Bob Liu <bob.liu@oracle.com>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Kyungmin Park <kyungmin.park@samsung.com>,
Dave Hansen <dave.hansen@intel.com>,
Minchan Kim <minchan@kernel.org>
Subject: Re: [PATCH v2 0/5] mm: migrate zbud pages
Date: Mon, 23 Sep 2013 12:19:16 -0500 [thread overview]
Message-ID: <20130923171916.GA23643@variantweb.net> (raw)
In-Reply-To: <5237FDCC.5010109@oracle.com>
On Tue, Sep 17, 2013 at 02:59:24PM +0800, Bob Liu wrote:
> Hi Krzysztof,
>
> On 09/11/2013 04:58 PM, Krzysztof Kozlowski wrote:
> > Hi,
> >
> > Currently zbud pages are not movable and they cannot be allocated from CMA
> > (Contiguous Memory Allocator) region. These patches add migration of zbud pages.
> >
>
> I agree that the migration of zbud pages is important so that system
> will not enter order-0 page fragmentation and can be helpful for page
> compaction/huge pages etc..
>
> But after I looked at the [patch 4/5], I found it will make zbud very
> complicated.
> I'd prefer to add this migration feature later until current version
> zswap/zbud becomes better enough and more stable.
I agree with this. We are also looking to add zsmalloc as an option too. It
would be nice to come up with a solution that worked for both (any) allocator
that zswap used.
>
> Mel mentioned several problems about zswap/zbud in thread "[PATCH v6
> 0/5] zram/zsmalloc promotion".
>
> Like "it's clunky as hell and the layering between zswap and zbud is
> twisty" and "I think I brought up its stalling behaviour during review
> when it was being merged. It would have been preferable if writeback
> could be initiated in batches and then waited on at the very least..
> It's worse that it uses _swap_writepage directly instead of going
> through a writepage ops. It would have been better if zbud pages
> existed on the LRU and written back with an address space ops and
> properly handled asynchonous writeback."
Yes, the laying in zswap vs zbud is wonky and should be addressed before adding
new layers.
>
> So I think it would be better if we can address those issues at first
> and it would be easier to address these issues before adding more new
> features. Welcome any ideas.
Agreed.
Seth
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WARNING: multiple messages have this Message-ID (diff)
From: Seth Jennings <sjenning@linux.vnet.ibm.com>
To: Bob Liu <bob.liu@oracle.com>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Kyungmin Park <kyungmin.park@samsung.com>,
Dave Hansen <dave.hansen@intel.com>,
Minchan Kim <minchan@kernel.org>
Subject: Re: [PATCH v2 0/5] mm: migrate zbud pages
Date: Mon, 23 Sep 2013 12:19:16 -0500 [thread overview]
Message-ID: <20130923171916.GA23643@variantweb.net> (raw)
In-Reply-To: <5237FDCC.5010109@oracle.com>
On Tue, Sep 17, 2013 at 02:59:24PM +0800, Bob Liu wrote:
> Hi Krzysztof,
>
> On 09/11/2013 04:58 PM, Krzysztof Kozlowski wrote:
> > Hi,
> >
> > Currently zbud pages are not movable and they cannot be allocated from CMA
> > (Contiguous Memory Allocator) region. These patches add migration of zbud pages.
> >
>
> I agree that the migration of zbud pages is important so that system
> will not enter order-0 page fragmentation and can be helpful for page
> compaction/huge pages etc..
>
> But after I looked at the [patch 4/5], I found it will make zbud very
> complicated.
> I'd prefer to add this migration feature later until current version
> zswap/zbud becomes better enough and more stable.
I agree with this. We are also looking to add zsmalloc as an option too. It
would be nice to come up with a solution that worked for both (any) allocator
that zswap used.
>
> Mel mentioned several problems about zswap/zbud in thread "[PATCH v6
> 0/5] zram/zsmalloc promotion".
>
> Like "it's clunky as hell and the layering between zswap and zbud is
> twisty" and "I think I brought up its stalling behaviour during review
> when it was being merged. It would have been preferable if writeback
> could be initiated in batches and then waited on at the very least..
> It's worse that it uses _swap_writepage directly instead of going
> through a writepage ops. It would have been better if zbud pages
> existed on the LRU and written back with an address space ops and
> properly handled asynchonous writeback."
Yes, the laying in zswap vs zbud is wonky and should be addressed before adding
new layers.
>
> So I think it would be better if we can address those issues at first
> and it would be easier to address these issues before adding more new
> features. Welcome any ideas.
Agreed.
Seth
next prev parent reply other threads:[~2013-09-23 17:40 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-11 8:58 [PATCH v2 0/5] mm: migrate zbud pages Krzysztof Kozlowski
2013-09-11 8:58 ` Krzysztof Kozlowski
2013-09-11 8:59 ` [PATCH v2 1/5] zbud: use page ref counter for " Krzysztof Kozlowski
2013-09-11 8:59 ` Krzysztof Kozlowski
2013-09-11 8:59 ` [PATCH v2 2/5] zbud: make freechunks a block local variable Krzysztof Kozlowski
2013-09-11 8:59 ` Krzysztof Kozlowski
2013-09-11 8:59 ` [PATCH v2 3/5] mm: use mapcount for identifying zbud pages Krzysztof Kozlowski
2013-09-11 8:59 ` Krzysztof Kozlowski
2013-09-11 8:59 ` [PATCH v2 4/5] mm: use indirect zbud handle and radix tree Krzysztof Kozlowski
2013-09-11 8:59 ` Krzysztof Kozlowski
2013-09-11 8:59 ` [PATCH v2 5/5] mm: migrate zbud pages Krzysztof Kozlowski
2013-09-11 8:59 ` Krzysztof Kozlowski
2013-09-17 6:59 ` [PATCH v2 0/5] " Bob Liu
2013-09-17 6:59 ` Bob Liu
2013-09-23 17:19 ` Seth Jennings [this message]
2013-09-23 17:19 ` Seth Jennings
2013-09-23 22:07 ` Seth Jennings
2013-09-23 22:07 ` Seth Jennings
2013-09-24 9:20 ` Krzysztof Kozlowski
2013-09-24 9:20 ` Krzysztof Kozlowski
2013-09-25 4:28 ` Bob Liu
2013-09-25 4:28 ` Bob Liu
2013-09-25 17:09 ` Tomasz Stanislawski
2013-09-25 17:09 ` Tomasz Stanislawski
2013-09-25 21:57 ` Seth Jennings
2013-09-25 21:57 ` Seth Jennings
2013-09-27 10:16 ` Tomasz Stanislawski
2013-09-27 10:16 ` Tomasz Stanislawski
2013-09-27 22:00 ` Seth Jennings
2013-09-27 22:00 ` Seth Jennings
2013-09-28 2:43 ` Bob Liu
2013-09-28 2:43 ` Bob Liu
2013-09-30 8:28 ` Krzysztof Kozlowski
2013-09-30 8:28 ` Krzysztof Kozlowski
2013-10-01 21:04 ` Seth Jennings
2013-10-01 21:04 ` Seth Jennings
2013-10-03 13:24 ` Krzysztof Kozlowski
2013-10-03 13:24 ` Krzysztof Kozlowski
2013-10-03 15:39 ` Seth Jennings
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