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 5/8] zsmalloc: introduce zs_can_compact() function
Date: Tue, 16 Jun 2015 23:41:06 +0900 [thread overview]
Message-ID: <20150616144106.GD20596@swordfish> (raw)
In-Reply-To: <20150616141914.GC31387@blaptop>
On (06/16/15 23:19), Minchan Kim wrote:
> On Fri, Jun 05, 2015 at 09:03:55PM +0900, Sergey Senozhatsky wrote:
> > This function checks if class compaction will free any pages.
> > Rephrasing -- do we have enough unused objects to form at least
> > one ZS_EMPTY page and free it. It aborts compaction if class
> > compaction will not result in any (further) savings.
> >
> > EXAMPLE (this debug output is not part of this patch set):
> >
> > -- class size
> > -- number of allocated objects
> > -- number of used objects,
> > -- estimated number of pages that will be freed
> >
> > [..]
> > class-3072 objs:24652 inuse:24628 maxobjs-per-page:4 pages-tofree:6
>
> Please use clear term. We have been used zspage as cluster of pages.
>
> maxobjs-per-zspage:4
>
OK, will correct.
class size
sats[OBJ_ALLOCATED]
stats[OBJ_USED]
get_maxobj_per_zspage()
+pages-per-zspage
zspages-to-free
> And say what is pages-per-zspage for each class.
> then, write how you calculate it for easy reviewing.
>
> * class-3072
> * pages-per-zspage: 3
> * maxobjs-per-zspage = 4
>
> In your example, allocated obj = 24652 and inuse obj = 24628
> so 24652 - 24628 = 24 = 4(ie, maxobjs-per-zspage) * 6
> so we can save 6 zspage. A zspage includes 3 pages so we can
> save 3 * 6 = 18 pages via compaction.
>
>
[..]
> > + * Make sure that we actually can compact this class,
> > + * IOW if migration will empty at least one page.
>
> free at least one zspage
OK.
> > + *
> > + * Should be called under class->lock
> > + */
> > +static unsigned long zs_can_compact(struct size_class *class)
> > +{
> > + /*
> > + * Calculate how many unused allocated objects we
> > + * have and see if we can free any zspages. Otherwise,
> > + * compaction can just move objects back and forth w/o
> > + * any memory gain.
> > + */
> > + unsigned long obj_wasted = zs_stat_get(class, OBJ_ALLOCATED) -
> > + zs_stat_get(class, OBJ_USED);
> > +
> > + obj_wasted /= get_maxobj_per_zspage(class->size,
> > + class->pages_per_zspage);
>
> I don't think we need division and make it simple.
>
> return obj_wasted >= get_maxobj_per_zspage
I use this number later for the shrinker, as a shrinker.count_objects()
return value (total number of zsages that can be freed).
-ss
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 5/8] zsmalloc: introduce zs_can_compact() function
Date: Tue, 16 Jun 2015 23:41:06 +0900 [thread overview]
Message-ID: <20150616144106.GD20596@swordfish> (raw)
In-Reply-To: <20150616141914.GC31387@blaptop>
On (06/16/15 23:19), Minchan Kim wrote:
> On Fri, Jun 05, 2015 at 09:03:55PM +0900, Sergey Senozhatsky wrote:
> > This function checks if class compaction will free any pages.
> > Rephrasing -- do we have enough unused objects to form at least
> > one ZS_EMPTY page and free it. It aborts compaction if class
> > compaction will not result in any (further) savings.
> >
> > EXAMPLE (this debug output is not part of this patch set):
> >
> > -- class size
> > -- number of allocated objects
> > -- number of used objects,
> > -- estimated number of pages that will be freed
> >
> > [..]
> > class-3072 objs:24652 inuse:24628 maxobjs-per-page:4 pages-tofree:6
>
> Please use clear term. We have been used zspage as cluster of pages.
>
> maxobjs-per-zspage:4
>
OK, will correct.
class size
sats[OBJ_ALLOCATED]
stats[OBJ_USED]
get_maxobj_per_zspage()
+pages-per-zspage
zspages-to-free
> And say what is pages-per-zspage for each class.
> then, write how you calculate it for easy reviewing.
>
> * class-3072
> * pages-per-zspage: 3
> * maxobjs-per-zspage = 4
>
> In your example, allocated obj = 24652 and inuse obj = 24628
> so 24652 - 24628 = 24 = 4(ie, maxobjs-per-zspage) * 6
> so we can save 6 zspage. A zspage includes 3 pages so we can
> save 3 * 6 = 18 pages via compaction.
>
>
[..]
> > + * Make sure that we actually can compact this class,
> > + * IOW if migration will empty at least one page.
>
> free at least one zspage
OK.
> > + *
> > + * Should be called under class->lock
> > + */
> > +static unsigned long zs_can_compact(struct size_class *class)
> > +{
> > + /*
> > + * Calculate how many unused allocated objects we
> > + * have and see if we can free any zspages. Otherwise,
> > + * compaction can just move objects back and forth w/o
> > + * any memory gain.
> > + */
> > + unsigned long obj_wasted = zs_stat_get(class, OBJ_ALLOCATED) -
> > + zs_stat_get(class, OBJ_USED);
> > +
> > + obj_wasted /= get_maxobj_per_zspage(class->size,
> > + class->pages_per_zspage);
>
> I don't think we need division and make it simple.
>
> return obj_wasted >= get_maxobj_per_zspage
I use this number later for the shrinker, as a shrinker.count_objects()
return value (total number of zsages that can be freed).
-ss
--
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 14:41 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 [this message]
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=20150616144106.GD20596@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.