From: Andrew Morton <akpm@linux-foundation.org>
To: Jason Mattax <jmattax@storytotell.org>
Cc: kamezawa.hiroyu@jp.fujitsu.com, cesarb@cesarb.net,
emunson@mgebm.net, penberg@kernel.org, linux-mm@kvack.org,
Hugh Dickins <hughd@google.com>
Subject: Re: Possible Swapfile bug
Date: Thu, 22 Mar 2012 12:46:35 -0700 [thread overview]
Message-ID: <20120322124635.85fd4673.akpm@linux-foundation.org> (raw)
In-Reply-To: <4F6B5236.20805@storytotell.org>
On Thu, 22 Mar 2012 10:24:22 -0600
Jason Mattax <jmattax@storytotell.org> wrote:
> Swapon very slow with swapfiles.
>
> After upgrading the kernel my swap file loads very slowly, while a swap
> partition is unaffected. With the newer kernel (2.6.33.1) I get
>
> # time swapon -v /var/swapfile
> swapon on /var/swapfile
> swapon: /var/swapfile: found swap signature: version 1, page-size 4,
> same byte order
> swapon: /var/swapfile: pagesize=4096, swapsize=6442450944,
> devsize=6442450944
>
> real 4m35.355s
> user 0m0.001s
> sys 0m1.786s
>
> while with the older kernel (2.6.32.27) I get
> # time swapon -v /var/swapfile
> swapon on /var/swapfile
> swapon: /var/swapfile: found swap signature: version 1, page-size 4,
> same byte order
> swapon: /var/swapfile: pagesize=4096, swapsize=6442450944,
> devsize=6442450944
>
> real 0m1.158s
> user 0m0.000s
> sys 0m0.876s
>
> this stays true even for new swapfiles I create with dd.
>
> the file is on an OCZ Vertex2 SSD.
Probably the vertex2 discard problem.
We just merged a patch which will hopefully fix it:
--- a/mm/swapfile.c~swap-dont-do-discard-if-no-discard-option-added
+++ a/mm/swapfile.c
@@ -2103,7 +2103,7 @@ SYSCALL_DEFINE2(swapon, const char __use
p->flags |= SWP_SOLIDSTATE;
p->cluster_next = 1 + (random32() % p->highest_bit);
}
- if (discard_swap(p) == 0 && (swap_flags & SWAP_FLAG_DISCARD))
+ if ((swap_flags & SWAP_FLAG_DISCARD) && discard_swap(p) == 0)
p->flags |= SWP_DISCARDABLE;
}
But Hugh doesn't like it and won't tell us why :)
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next prev parent reply other threads:[~2012-03-22 19:46 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-22 16:24 Jason Mattax
2012-03-22 19:46 ` Andrew Morton [this message]
2012-03-23 0:49 ` Jason Mattax
2012-03-23 12:05 ` Hugh Dickins
2012-03-24 3:56 ` Jason Mattax
2012-03-25 19:39 ` Hugh Dickins
2012-03-25 21:21 ` Jason Mattax
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