From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [RFC][PATCHv2 3/8] zsmalloc: lower ZS_ALMOST_FULL waterline
Date: Tue, 16 Jun 2015 23:35:03 +0900 [thread overview]
Message-ID: <20150616143503.GC20596@swordfish> (raw)
In-Reply-To: <20150616133708.GB31387@blaptop>
On (06/16/15 22:37), Minchan Kim wrote:
> On Fri, Jun 05, 2015 at 09:03:53PM +0900, Sergey Senozhatsky wrote:
> > get_fullness_group() considers 3/4 full pages as almost empty.
> > That, unfortunately, marks as ALMOST_EMPTY pages that we would
> > probably like to keep in ALMOST_FULL lists.
> >
> > ALMOST_EMPTY:
> > [..]
> > inuse: 3 max_objects: 4
> > inuse: 5 max_objects: 7
> > inuse: 5 max_objects: 7
> > inuse: 2 max_objects: 3
> > [..]
> >
> > For "inuse: 5 max_objexts: 7" ALMOST_EMPTY page, for example,
> > it'll take 2 obj_malloc to make the page FULL and 5 obj_free to
> > make it EMPTY. Compaction selects ALMOST_EMPTY pages as source
> > pages, which can result in extra object moves.
> >
> > In other words, from compaction point of view, it makes more
> > sense to fill this page, rather than drain it.
> >
> > Decrease ALMOST_FULL waterline to 2/3 of max capacity; which is,
> > of course, still imperfect, but can shorten compaction
> > execution time.
>
> However, at worst case, once compaction is done, it could remain
> 33% fragment space while it can remain 25% fragment space in current.
> Maybe 25% wouldn't enough so we might need to scan ZS_ALMOST_FULL as
> source in future. Anyway, compaction is really slow path now so
> I prefer saving memory space by reduce internal fragmentation to
> performance caused more copy of objects.
>
Well, agree. I think we can drop this one from the series for now.
It's very hard to support this patch with any numbers, etc. because
it depends on things that are out of zram/zsmalloc control -- IO and
data patterns.
(opposing this patch is also very hard, due to exactly same reason).
-ss
> >
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> > ---
> > mm/zsmalloc.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> > index cd37bda..b94e281 100644
> > --- a/mm/zsmalloc.c
> > +++ b/mm/zsmalloc.c
> > @@ -198,7 +198,7 @@ static int zs_size_classes;
> > *
> > * (see: fix_fullness_group())
> > */
> > -static const int fullness_threshold_frac = 4;
> > +static const int fullness_threshold_frac = 3;
> >
> > struct size_class {
> > /*
> > @@ -633,7 +633,7 @@ static enum fullness_group get_fullness_group(struct page *page)
> > fg = ZS_EMPTY;
> > else if (inuse == max_objects)
> > fg = ZS_FULL;
> > - else if (inuse <= 3 * max_objects / fullness_threshold_frac)
> > + else if (inuse <= 2 * max_objects / fullness_threshold_frac)
> > fg = ZS_ALMOST_EMPTY;
> > else
> > fg = ZS_ALMOST_FULL;
> > --
> > 2.4.2.387.gf86f31a
> >
>
> --
> Kind regards,
> Minchan Kim
>
WARNING: multiple messages have this Message-ID (diff)
From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [RFC][PATCHv2 3/8] zsmalloc: lower ZS_ALMOST_FULL waterline
Date: Tue, 16 Jun 2015 23:35:03 +0900 [thread overview]
Message-ID: <20150616143503.GC20596@swordfish> (raw)
In-Reply-To: <20150616133708.GB31387@blaptop>
On (06/16/15 22:37), Minchan Kim wrote:
> On Fri, Jun 05, 2015 at 09:03:53PM +0900, Sergey Senozhatsky wrote:
> > get_fullness_group() considers 3/4 full pages as almost empty.
> > That, unfortunately, marks as ALMOST_EMPTY pages that we would
> > probably like to keep in ALMOST_FULL lists.
> >
> > ALMOST_EMPTY:
> > [..]
> > inuse: 3 max_objects: 4
> > inuse: 5 max_objects: 7
> > inuse: 5 max_objects: 7
> > inuse: 2 max_objects: 3
> > [..]
> >
> > For "inuse: 5 max_objexts: 7" ALMOST_EMPTY page, for example,
> > it'll take 2 obj_malloc to make the page FULL and 5 obj_free to
> > make it EMPTY. Compaction selects ALMOST_EMPTY pages as source
> > pages, which can result in extra object moves.
> >
> > In other words, from compaction point of view, it makes more
> > sense to fill this page, rather than drain it.
> >
> > Decrease ALMOST_FULL waterline to 2/3 of max capacity; which is,
> > of course, still imperfect, but can shorten compaction
> > execution time.
>
> However, at worst case, once compaction is done, it could remain
> 33% fragment space while it can remain 25% fragment space in current.
> Maybe 25% wouldn't enough so we might need to scan ZS_ALMOST_FULL as
> source in future. Anyway, compaction is really slow path now so
> I prefer saving memory space by reduce internal fragmentation to
> performance caused more copy of objects.
>
Well, agree. I think we can drop this one from the series for now.
It's very hard to support this patch with any numbers, etc. because
it depends on things that are out of zram/zsmalloc control -- IO and
data patterns.
(opposing this patch is also very hard, due to exactly same reason).
-ss
> >
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> > ---
> > mm/zsmalloc.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> > index cd37bda..b94e281 100644
> > --- a/mm/zsmalloc.c
> > +++ b/mm/zsmalloc.c
> > @@ -198,7 +198,7 @@ static int zs_size_classes;
> > *
> > * (see: fix_fullness_group())
> > */
> > -static const int fullness_threshold_frac = 4;
> > +static const int fullness_threshold_frac = 3;
> >
> > struct size_class {
> > /*
> > @@ -633,7 +633,7 @@ static enum fullness_group get_fullness_group(struct page *page)
> > fg = ZS_EMPTY;
> > else if (inuse == max_objects)
> > fg = ZS_FULL;
> > - else if (inuse <= 3 * max_objects / fullness_threshold_frac)
> > + else if (inuse <= 2 * max_objects / fullness_threshold_frac)
> > fg = ZS_ALMOST_EMPTY;
> > else
> > fg = ZS_ALMOST_FULL;
> > --
> > 2.4.2.387.gf86f31a
> >
>
> --
> Kind regards,
> Minchan Kim
>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2015-06-16 14:36 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 [this message]
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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20150616143503.GC20596@swordfish \
--to=sergey.senozhatsky@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=minchan@kernel.org \
--cc=sergey.senozhatsky.work@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.