On 03/22/2012 01:46 PM, Andrew Morton wrote:
On Thu, 22 Mar 2012 10:24:22 -0600
Jason Mattax<jmattax@xxxxxxxxxxxxxxx> 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 :)
Patch worked like a charm for me, thanks.
--
Jason Mattax
575-418-1791
jmattax@xxxxxxxxxxxxxxx
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